SPECTROMETRY SYSTEM WITH VISIBLE AIMING BEAM
A handheld spectrometer can be configured with a visible aiming beam to allow the user to determine the measured region of the object. When the visible aiming beam comprises the spectrometer measurement beam, the spectrometer measurement beam comprises sufficient energy for the user to see the measurement beam illuminating the object. When the visible aiming beam comprises a separate beam, the visible aiming beam comprises sufficient energy for the user to see a portion of the aiming beam reflected from the object. The visible aiming beam and measurement beam can be arranged to at least partially overlap on the sample, such that the user has an indication of the area of the sample being measured.
The present application is a continuation of International Patent Application No. PCT/IL2016/050130, filed Feb. 4, 2016, entitled “SPECTROMETRY SYSTEM WITH VISIBLE AIMING BEAM” (attorney docket no. 45151-706.601), which claims the benefit of U.S. Provisional Application Ser. No. 62/112,553, filed on Feb. 5, 2015, entitled “Spectrometry System with Visible Aiming Beam” (attorney docket no. 45151-706.101), U.S. Provisional Application Ser. No. 62/154,585, filed on Apr. 29, 2015, entitled “Spectrometry System with Visible Aiming Beam” (attorney docket no. 45151-706.102), U.S. Provisional Application Ser. No. 62/161,728, filed on May 14, 2015, entitled “Spectrometry System with Visible Aiming Beam” (attorney docket no. 45151-706.103), U.S. Provisional Application Ser. No. 62/190,524, filed on Jul. 9, 2015, entitled “Spectrometry System with Visible Aiming Beam” (attorney docket no. 45151-706.104), U.S. Provisional Application Ser. No. 62/258,341, filed on Nov. 20, 2015, entitled “Spectrometry System with Visible Aiming Beam” (attorney docket no. 45151-706.105), and U.S. Provisional Application Ser. No. 62/277,558, filed on Jan. 12, 2016, entitled “Spectrometry System with Visible Aiming Beam” (attorney docket no. 45151-706.106), the entire disclosures of each of which are incorporated herein by reference.
INCORPORATION BY REFERENCEAll publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.
BACKGROUND OF THE INVENTIONSpectrometers are used for many purposes. For example, spectrometers are used in the detection of defects in industrial processes, satellite imaging, and laboratory research. However, these instruments have typically been too large and too costly for the consumer market.
Spectrometers detect radiation from a sample and process the resulting signal to obtain and present information about the sample that includes spectral, physical and chemical information about the sample. These instruments generally include some type of spectrally selective element to separate wavelengths of radiation received from the sample, and a first-stage optic, such as a lens, to focus or concentrate the radiation onto an imaging array.
The prior spectrometers can be less than ideal in at least some respects. Prior spectrometers having high resolution can be larger than ideal for use in many portable applications. Although prior spectrometers with decreased size have been proposed, the prior spectrometers having decreased size and optical path length can have less than ideal resolution, sensitivity and less accuracy than would be ideal. Also, the cost of prior spectrometers can be greater than would be ideal. The prior spectrometers can be somewhat bulky, difficult to transport and the optics can require more alignment than would be ideal in at least some instances.
Further, data integration of prior spectrometers with measured objects can be less than ideal in at least some instances. For example, although prior spectrometers can provide a spectrum of a measured object, the spectrum may be of little significance to at least some users. It would be helpful if a spectrum of a measured object could be associated with attributes of the measured object that are useful to a user. For example, although prior spectrometers may be able to measure sugar, it would be helpful if a spectrometer could be used to determine the sweetness of an object such as an apple. Many other examples exist where spectral data alone does not adequately convey relevant attributes of an object, and it would be helpful to provide attributes of an object to a user in response to measured spectral data.
Prior spectrometer methods and apparatus may have less than ideal aiming characteristics. Prior illumination apparatus for spectrometers may have less specificity and accuracy than would be ideal. Further the prior spectrometer illumination devices may output more light energy than would be ideal. Also, in some situations it can be difficult for a user to know what area of an object is being measured.
In light of the above, an improved spectrometer and interpretation of spectral data that overcomes at least some of the above mentioned deficiencies of the prior spectrometers would be beneficial. Ideally, such a spectrometer would be compact, easy to aim, integrated with a consumer device such as a cellular telephone, sufficiently rugged and low in cost to be practical for end-user spectroscopic measurements of items, and convenient to use. Further, it would be helpful to provide data comprising attributes of measured objects related to the spectral data of the objects to many people.
SUMMARY OF THE INVENTIONThe present disclosure provides improved spectrometer methods and apparatus. A spectrometer may be used to determine one or more spectra of an object, and the one or more spectra may be associated with one or more attributes of the object that are relevant to the user. While the spectrometer can take many forms, in many instances the spectrometer comprises a hand held spectrometer with wavelength multiplexing in which a plurality of wavelengths are used to illuminate the object and measure the one or more spectra. The handheld spectrometer can be configured with a visible aiming beam to allow the user to determine the measured region of the object. The visible aiming beam may comprise the spectrometer measurement beam, or a separate beam. When the visible aiming beam comprises the spectrometer measurement beam, the spectrometer measurement beam comprises sufficient energy for the user to see the measurement beam illuminating the object. When the visible aiming beam comprises a separate beam, the visible aiming beam comprises sufficient energy for the user to see a portion of the aiming beam reflected from the object. The visible aiming beam and measurement beam can be arranged to at least partially overlap on the sample, such that the user has an indication of the area of the sample being measured. The spectrometer may comprise a field of view, and the measurement beam illuminating the sample may occupy only a portion of the field of view of the spectrometer, such that the region of the sample measured is defined with the measurement beam. The measurement beam may overlap with the visible aiming beam such that the visible aiming beam identifies the measurement area of the sample for the user. This identification of the area of the sample to be measured can help the user aim the hand held spectrometer and provide improved measurement accuracy with decreased artifacts. The measurement beam can be coupled to the aiming beam in one or more of many ways with one or more of many configurations, such as a coaxial configuration in which the measurement bean and aiming beam extend coaxially together along a shared optical axis.
The spectral data of the object can be used to determine one or more attributes of the object. In many instances, the spectrometer is coupled to a database of spectral information that can be used to determine the attributes of the object. The spectrometer system may comprise a hand held communication device coupled to a spectrometer, in which the user can input and receive data related to the measured object with the hand held communication device. The configurations disclosed herein allow many users to share object data with many people, in order to provide many people with actionable intelligence in response to spectral data.
In one aspect, an apparatus to measure spectra of a sample comprises a detector and a light source. The detector has a field of view to measure the spectra of the sample within the field of view. The light source is configured to direct an optical beam to the sample within the field of view, wherein a portion of the optical beam reflected from the sample is visible to a user. The portion of the optical beam reflected from the sample visible to the user may define a measurement area of the sample.
The apparatus may further comprise a casing supported with the detector and the light source. The detector and the light source may be arranged to fit within the casing. The casing may be sized to fit within a hand of the user, to allow the user to aim the spectrometer at the sample and measure the sample. The apparatus may further comprise a user input supported with the casing. The user input may be arranged for the user to aim the spectrometer and measure the sample with the user input manipulated with the hand holding the spectrometer. The apparatus may further comprise circuitry coupled to the detector and the light source. The circuitry may be configured to transmit the optical beam in response to the user input with the hand holding the hand held spectrometer.
The light source of the apparatus may be configured in order to provide the optical beam incident on the sample with an illuminance (Ev) within a range from about 20 lux (lm/m2) to about 100,000 lux (lm/m2). The light source may be configured to provide the optical beam incident on the sample with an irradiance within a range from about 0.1 mW/cm2 to about 100 mW/cm2.
The portion of the optical beam visible to the user may comprise a portion of a measurement beam to measure the spectra of the sample. The portion of the optical beam visible to the user may further comprise an aiming beam comprising one or more wavelengths corresponding to one or more colors visible to the user. The one or more colors visible to the user may comprise one or more of red, orange, yellow, blue, green, indigo or violet. The portion of the beam visible to the user may comprise a combination of visible wavelengths of light.
The optical beam may comprise an aiming beam and a measurement beam arranged to illuminate the sample within the field of view of the detector. The detector may comprise one or more filters to inhibit transmission of the aiming beam and to transmit the measurement beam. The one or more filters may comprise a plurality of optical filters to inhibit transmission of a portion of the aiming beam reflected from the sample and to transmit a portion of the measurement beam reflected from the sample. The detector may comprise a plurality of optical channels, each of the plurality of optical filters corresponding to an optical channel, and each optical channel comprising a field of view. The field of view of the detector may comprise a plurality of overlapping fields of view of a plurality of optical channels, wherein the aiming beam and the measurement beam may be arranged to overlap with the plurality of overlapping fields of view on the object.
The apparatus may further comprise a second light source to direct a measurement beam toward the sample, the first light source comprising an aiming beam. The measurement beam may comprise an infrared beam and the aiming beam may comprise a visible light beam.
The apparatus may further comprise one or more optics coupled to the light source to direct the optical beam toward the sample. The one or more optics may comprise one or more of a mirror, a beam splitter, a lens, a curved reflector, or a parabolic reflector to direct the optical beam toward the sample. The light source may comprise a visible light source to generate an aiming beam and a measurement beam light source to generate a measurement beam, wherein the one or more optics may be arranged to receive the aiming beam and the measurement beam and direct the aiming beam and the measurement beam toward the sample with the aiming beam and the measurement beam overlapping on the sample. The measurement beam light source may comprise a phosphorescent plate, and the visible light source may comprise one or more of a laser diode or an LED emitting visible light energy having one or more wavelengths within a range from about 400 to 800 nm. The phosphorescent plate and the one or more of the laser diode or the LED may be arranged coaxially in order to transmit the measurement beam and the aiming beam along a common optical axis. The phosphorescent plate may be positioned to receive the visible light energy from the one or more of the laser diode or the LED. The aiming beam may comprise a portion of the visible light energy transmitted through the phosphorescent plate, and the measurement light beam may comprise light energy generated with the phosphorescent plate.
The measurement beam may be configured to illuminate a measurement area of the sample, and the aiming beam may be configured to illuminate a visible area of the sample overlapping with the measurement area, in order to display the measurement area to the user. The visible area may comprise from about 50% to about 150/o or from about 75% to about 125% of the measurement area. The visible area may comprise at least about 90%, at least about 95%, or at least about 99% of of the measurement area. The one or more optics and the aiming beam and the measurement beam may be arranged to direct the aiming beam extending along an aiming beam axis and the measurement beam extending along a measurement beam axis toward the sample, wherein the aiming beam axis may be co-axial with the measurement beam axis.
The detector and the light source may comprise components of a spectrometer having a volume within a range from about 1 cm3 to about 200 cm3. The detector and the light source may comprise components of a spectrometer having dimensions within a range from about 0.1 cm×0.1 cm×2 cm to about 5 cm×5 cm×10 cm. The detector and the light source may comprise components of a spectrometer having a weight within a range from about 1 g to about 100 g. The detector and the light source may comprise components of a spectrometer having an optical resolution of less than 10 nm. The light source may emit electromagnetic energy comprising one or more of ultraviolet, visible, near infrared, or infrared light energy.
In another aspect, a method of measuring spectra of a sample comprises providing a detector having a field of view to measure the spectra of the sample within the field of view. The method further comprises providing a light source to direct an optical beam to the sample within the field of view, wherein a portion of the optical beam reflected from the sample is visible to a user.
The accuracy and reliability of measurements made by the spectrometer may be improved by providing a spectrometer system configured to reduce the system's sensitivity to the spatial distribution of light on the diffuser. To reduce the dependence of detected intensity distributions of incident light on spatial variations of the light intensity on the diffuser near a diffuser plane, a filter assembly comprising a diffuser and an optical filter may be provided with the spectrometer system. The filter assembly may comprise two or more of an optical substrate, an optical filter such as an interference filter, and a diffuser, integrated into a single optical component. The optical substrate can, for example, comprise a bulk visible light filter, configured to block out wavelengths that are outside the operational range of the spectrometer. In addition to improving the accuracy and reliability of the spectrometer measurements, by integrating the functions of a visible light filter, diffuser, and/or optical filter into a single optical component, the total cost of production and the size of the spectrometer can be reduced. The filter assembly may further comprise a lens or a lens array coupled directly thereto. In a spectrometer system comprising a plurality of optical channels, the filter assembly may be coupled to an aperture array comprising a plurality of apertures having different sizes, so as to balance the intensity of incident light transmitted through the filters across the different channels of the system.
The light beam may comprise a modulated light beam, and the circuitry can be coupled to the light source and detector and configured to measure the sample with the modulated light beam, in order to inhibit noise from ambient light sources. The modulated light beam may comprise visible light, and the light beam can be modulated with frequencies away from a frequency peak of the ambient light. The modulated light beam may comprise a modulation frequency within a range from about 10 Hz to about 45 Hz, or within a range from about 65 Hz to about 90 Hz, for example. Alternatively or in combination, the circuitry can be configured to measure the sample with one or more dark field samples and one or more pulsed samples to inhibit ambient light noise. The modulated light beam is well suited for use in combination with many spectrometers, such as spectrometers comprising a filter array or spectrometers comprising a plurality of light sources having different wavelengths, and combinations thereof.
The spectrometer module of the compact spectrometer may comprise a support array configured to increase the spectral range of the spectrometer. The support array can be disposed between the lens array and the image sensor to provide a plurality of isolated optical channels extending from a lens of the lens array and a corresponding sensor area of the image sensor. Each channel of the support array may be defined by a first opening facing the lens array, a second opening facing the image sensor, and a channel wall extending therebetween. The support array may be configured such that the channel wall extends all the way to the image sensor, such that crosstalk between adjacent optical channels can be inhibited, for example minimized. Inhibiting the crosstalk between channels can allow the sampling of a larger portion of the image sensor without detecting stray light, such that the area of the image generated on the image sensor by light from each channel can be increased substantially, for example maximized. Alternatively or in combination, each channel of the support array may be configured to have a round-shaped first opening facing the lens array and a rectangular or square-shaped opening facing the image sensor. Such a configuration can provide rectangular or square-shaped images of light on the image sensor. The rectangular or square-shaped images can collect additional spectral information compared to round-shaped images. The additional spectral information can comprise information from light having higher angles of incidence, enabling the sensor area corresponding to each optical channel to detect an extended spectral range of incident light.
In another aspect, an apparatus to measure spectra of a sample comprises a filter array comprising a plurality of filters, a lens array comprising a plurality of lenses, an image sensor comprising a plurality of sensor areas, and at least one diffuser. The filter array may be configured to receive light from the sample, the lens array configured to receive light transmitted through the filter array, and the image sensor configured to receive light transmitted through the lens array. The diffuser may be configured to spatially distribute the light from the sample substantially evenly across a front surface of the apparatus.
The at least one diffuser may comprise three or more diffusers arranged sequentially along an optical path of the light from the sample. The at least one diffuser may comprise a lateral diffuser configured to receive input light having a first lateral distribution and transmit output light having a second lateral distribution greater than the first lateral distribution. The lateral diffuser may comprise a plurality of scattering structures. The plurality of scattering structures may comprise a refractive index that is greater than a refractive index of a support material surround the plurality of scattering structures. The lateral diffuser may comprise a plurality of non-overlapping scattering structures. The plurality of scattering structures comprises a plurality of particles, a plurality of pores, or a combination thereof. The plurality of scattering structures may have a size and a density per unit volume, the lateral diffuser may comprise a thickness, and the thickness of the lateral diffuser and the size and density of the plurality of scattering structures mat be arranged such that a majority of light exiting the lateral diffuser is scattered by at least two light scattering structures.
In another aspect, an apparatus to measure spectra of a sample comprises a diffuser, a filter array comprising a plurality of filters, a lens array comprising a plurality of lenses, and an image sensor comprising a plurality of sensor areas. The apparatus further comprises an aperture array disposed between the diffuser and the lens array, and a support array disposed between the lens array and the image sensor. The diffuser may be configured to receive light from the sample, the filter array configured to receive light transmitted through the diffuser, the lens array configured to receive light transmitted through the filter array, and the image sensor configured to receive light transmitted through the lens array. The aperture array may comprise a plurality of apertures configured to pass light from the diffuser to the lens array, and the support array may comprise a plurality of channels configured to pass light from the lens array to the image sensor. The aperture array and the support array may be collectively configured to selectively pass light from the sample incident on a front surface of the apparatus at an angle of incidence within a predetermined range.
The aperture array may comprise a first aperture array layer and a second aperture array layer. The first aperture array layer may be disposed between the diffuser and the filter array, and may comprise a first plurality of apertures. The second aperture array layer may be disposed between the filter array and the lens array, and comprise a second plurality of apertures aligned with the first plurality of apertures. The first and second aperture layers may be arranged to block light having an angle of incidence outside the predetermined range from passing through to the lens array.
Each of the first plurality of apertures may have a first diameter, each of the second plurality of apertures may have a second diameter, and the first aperture layer array and the second aperture array layer may be separated by a separation distance. One or more of the first diameter, the second diameter, and the separation distance may be arranged to block light have the angle of incident outside the predetermined range. The first diameter may be greater than the second diameter, the second diameter may be greater than the first diameter, or the first diameter and the second diameter may be equal.
The filter array may comprise an opaque material disposed between adjacent filters of the plurality of filters. The opaque material may be configured to prevent cross-talk of light between the adjacent filters.
A side wall of each of the plurality of channels of the support array may be configured to reduce an intensity of light by at least about 90% after a single reflection of the light from the side wall. Each of the plurality of channels of the support array may be shaped substantially as a frustum, wherein a top opening of the channel is smaller than a bottom opening of the channel. Each channel may comprise a continuous, rounded side wall, or each channel may comprise two or more side walls connected at an angle relative to one another. Each channel may comprise three or more straight side walls connected at one or more angles relative to one another, such that a horizontal cross-section of the channel forms a polygon. The two or more side walls may be arranged such that light entering the channel is reflected from the two or more side walls at least two times before exiting the channel. A side wall of each of the plurality of channels of the support array may be configured to provide substantially specular reflection of light from the side wall, or substantially diffusive reflection of light from the side wall.
Each of the plurality of channels of the support array may comprise one or more side walls extending from a top end of the channel to a bottom end of the channel, and a bottom wall extending over the bottom end. The bottom wall may comprise a central opening therethrough, wherein an area of the central opening is smaller than a cross-sectional area of the channel at the bottom end. The one or more side walls and the bottom wall may be arranged to selectively allow the light having the angle of incidence within the predetermined range to pass through the central opening and exit the channel.
The apparatus may further comprise an angle limiting layer disposed between the diffuser and the filter array, wherein the angle limiting layer is configured to selectively allow the light having the angle of incidence within the predetermined range to pass therethrough. The angle limiting layer may comprise a micro-louver film having a plurality of light transmissive sections and a plurality of light blocking sections arranged alternatingly along a length of the micro-louver film. One or more of a thickness of the micro-louver film and a distance between adjacent light blocking sections may be configured to selectively allows the light having the angle of incidence within the predetermined range to pass through to the filter array. The angle limiting layer may comprises a prism film having an input surface configured to receive light and an output surface configured to output the light, the output surface comprising a plurality of microstructures configured to modify an angle of transmission of the output light. The plurality of microstructures may be configured to output light selectively comprising the light having the angle of incidence within the predetermined range. The plurality of microstructures may be further configured to redirect light having an angle of incidence greater than a predetermined threshold value to adjacent microstructures or back towards the diffuser. The plurality of microstructures may comprise a plurality of pyramid shaped structures.
In the following description, various aspects of the invention will be described. For the purposes of explanation, specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent to one skilled in the art that there are other embodiments of the invention that differ in details without affecting the essential nature thereof. Therefore the invention is not limited by that which is illustrated in the figure and described in the specification, but only as indicated in the accompanying claims, with the proper scope determined only by the broadest interpretation of said claims.
A better understanding of the features and advantages of the present disclosure will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of embodiments of the present disclosure are utilized, and the accompanying drawings.
The configurations disclosed herein can be combined in one or more of many ways to provide improved spectrometer methods and apparatus. One or more components of the configurations disclosed herein can be combined with each other in many ways. A spectrometer as described herein can be used to generate spectral data of the object, and the spectral data of the object transmitted to a cloud based server in order to determine one or more attributes of the object. Alternatively or in combination, data of the cloud based server can be made available to both users and non-users of the spectrometers in order to provide useful information related to attributes of measured objects. The data of the cloud based server can be made available to users and non-users in many ways, for example with downloadable apps capable of connecting to the cloud based server and downloading information related to spectra of many objects.
The configurations disclosed herein are also capable of providing a database of attributes of many objects related to spectral data. A mobile communication device can be configured for a user to input attributes of one or more measured objects in order to construct a database based on spectral data of many measured objects.
As used herein, like characters refer to like elements. As used herein, the term “light” encompasses electromagnetic radiation having wavelengths in one or more of the ultraviolet, visible, or infrared portions of the electromagnetic spectrum. As used herein, the term “dispersive” is used, with respect to optical components, to describe a component that is designed to separate spatially, the different wavelength components of a polychromatic beam of light. Non-limiting examples of “dispersive” optical elements by this definition include diffraction gratings and prisms. The term specifically excludes elements such as lenses that disperse light because of non-idealities such as chromatic aberration or elements such as interference filters that have different transmission profiles according to the angle of incident radiation. The term also excludes the filters and filter matrixes described herein. As used herein, the term “store” encompasses a structure that stores objects, such as a crate or building.
The dimensions of an optical beam as described herein can be determined in one or more of many ways. The size of the beam may comprise a full width half maximum of the beam, for example. The measurement beam may comprise blurred edges, and the measurement area of the beam defining the measurement area of the sample may comprise a portion of the beam extending beyond the full width half maximum of the beam, for example. The dimensions of the aiming beam can be similarly determined.
Overview of Compact Spectrometer System
The spectrometer system may allow multiple users to connect to the cloud based server 118 via their hand held devices 110, as described in further detail herein. In some instances, the server 118 may be configured to simultaneously communicate with up to millions of hand held devices 110. The ability of the system to support a large number of users and devices at the same time can allow users of the system to access, in some instances in real-time, large amounts of information relating to a material of interest. Access to such information may provide users with a way of making informed decisions relating to a material of interest.
The hand held device 110 may comprise one or more components of a smart phone, such as a display 112, an interface 114, a processor, a computer readable memory and communication circuitry. The device 110 may comprise a substantially stationary device when used, such as a wireless communication gateway, for example.
The processor 106 may comprise a tangible medium embodying instructions, such as a computer readable memory embodying instructions of a computer program. Alternatively or in combination the processor may comprise logic such as gate array logic in order to perform one or more logic steps.
The sensor module 130 can enable the identification of the sample material based on non-spectroscopic information in addition to the spectroscopic information measured by the spectrometer module 160. Such a dual information system may enhance the accuracy of detection or identification of the material.
The sensor element of sensor module 130 may comprise any sensor configured to generate a non-spectroscopic signal associated with at least one aspect of the environment, including the material being analyzed. For example, the sensor element may comprise one or more of a camera, temperature sensor, electrical sensor (capacitance, resistance, conductivity, inductance), altimeter, GPS unit, turbidity sensor, pH sensor, accelerometer, vibration sensor, biometric sensor, chemical sensor, color sensor, clock, ambient light sensor, microphone, penetrometer, durometer, barcode reader, flowmeter, speedometer, magnetometer, and another spectrometer.
The output of the sensor module 130 may be associated with the output of the spectrometer module 160 via at least one processing device of the spectrometer system. The processing device may be configured to receive the outputs of the spectrometer module and sensor module, analyze both outputs, and based on the analysis provide information relating to at least one characteristic of the material to a display unit. A display unit may be provided on the device in order to allow display of such information.
The spectrometer module 160 may comprise one or more lens elements. Each lens can be made of two surfaces, and each surface may be an aspheric surface. In designing the lens for a fixed-focus system, it may be desirable to reduce the system's sensitivity to the exact location of the optical detector on the z-axis (the axis perpendicular to the plane of the optical detector), in order to tolerate larger variations and errors in mechanical manufacturing. To do so, the point-spread-function (PSF) size and shape at the nominal position may be traded off with the depth-of-field (DoF) length. For example, a larger-than-optimal PSF size may be chosen in return for an increase in the DoF length. One or more of the aspheric lens surfaces of each lens of a plurality of lenses can be shaped to provide the increased PSF size and the increased DoF length for each lens. Such a design may help reduce the cost of production by enabling the use of mass production tools, since mass production tools may not be able to meet stringent tolerance requirements associated with systems that are comparatively more sensitive to exact location of the optical detector.
In some cases, the measurement of the sample may be performed using scattered ambient light. In some cases, the spectrometer system may comprise a light or illumination source, such as illumination module 140. The light source can be of any type (e.g., laser, light-emitting diode, etc.) known in the art appropriate for the spectral measurements to be made. The light source may emit from 350 nm to 1100 nm. The light source may emit from 0.1 mW to 500 mW. The wavelength(s) and intensity of the light source can depend on the particular use to which the spectrometer will be put.
The spectrometer may also include a power source, such as a battery or power supply. In some instances the spectrometer is powered by a power supply from a consumer hand held device (e.g. a cell phone). In some instances the spectrometer has an independent power supply. In some instances a power supply from the spectrometer can supply power to a consumer hand held device.
The spectrometer as described herein can be adapted, with proper choice of light source, detector, and associated optics, for a use with a wide variety of spectroscopic techniques. Non-limiting examples include Raman, fluorescence, and IR or UV-VIS reflectance and absorbance spectroscopies. Because, as described herein, a compact spectrometer system can separate a Raman signal from a fluorescence signal, the same spectrometer may be used for both spectroscopies. The spectrometer may not comprise a monochromator.
Referring again to
When a user initiates a measurement of a sample material S using the spectrometer 102, for example by pressing the operating button 1006 with hand H, the spectrometer emits an optical beam 10 toward the sample material within the field of view 40. When the optical beam 10 hits the sample material S, the light may be partially absorbed and/or partially reflected by the sample material; alternatively or in combination, optical beam 10 may cause the sample material to emit light in response. The detector of the spectrometer module 160 may be configured to sense at least a portion of the optical beam 10 reflected back by the sample and/or light emitted by the sample in response to the optical beam 10, and consequently generate the spectral data of the sample material as described in further detail herein.
The spectrometer 102 may be configured to begin measurement of a sample material S with just ambient light, without the optical beam 10. After completing the measurement with ambient light only, the illumination module 140 of the spectrometer 102 can generate the optical beam 10, and the spectrometer module 160 can begin measurement of the sample material with the optical beam 10. In this case, there may be a brief time lapse between the initiation of a measurement, for example by a user pressing the operating button 1006, and the generation of the optical beam 10 and the visible portions thereof. The ambient light-only measurement can be used to reduce or eliminate the contribution of ambient light in the spectral data of the sample material S. For example, the measurement made with ambient light only can be subtracted from the measurement made with the optical beam 10.
A portion of the optical beam 10 that is reflected from the sample material S may be visible to the user; this visible, reflected portion of optical beam 10 may define the measurement area 50 of the sample material S. The measurement area 50 of the sample may at least partially overlap with and fall within the field of view 40 of the detector of the spectrometer. The area covered by the field of view 40 may be larger than the visible area of the sample illuminated by the optical beam 10, or the measurement area 50 defined by the visible portion of the optical beam 10. Alternatively, the field of view may be smaller than the optical beam, for example. In many configurations, the field of view 40 of the detector of the spectrometer module is larger than the area illuminated by the optical beam 10, and hence the measurement area 50 is defined by the optical beam 10 rather than by the field of view 40 of the detector.
The visible portion of optical beam 10 may comprise one or more wavelengths corresponding to one or more colors visible to the user. For example, the visible portion of optical beam 10 may comprise one or more wavelengths corresponding to the colors red, orange, yellow, blue, green, indigo, violet, or a combination thereof. The visible portion of optical beam 10 reflected from the sample material S may comprise about 0.1% to about 10%, about 1% to about 4%, or about 2% to about 3% of optical beam 10. The visible portion of optical beam 10 may comprise light operating with power in a range from about 0.1 mW to about 100 mW, about 1 mW to about 75 mW, about 1 mW to about 50 mW, about 5 mW to about 40 mW, about 5 mW to about 30 mW, about 5 mW to about 20 mW, or about 10 mW to about 15 mW. The visible portion of optical beam 10 incident on the sample may have an intensity in a range from about 0.1 mW to about 100 mW, about 1 mW to about 75 mW, about 1 mW to about 50 mW, about 5 mW to about 40 mW, about 5 mW to about 30 mW, about 5 mW to about 20 mW, or about 10 mW to about 15 mW. The visible portion of optical beam 10 incident on the sample may have an intensity or total light output in a range from about 0.001 lumens to about 10 lumens, about 0.001 lumens to about 5 lumens, about 0.005 lumens to about 10 lumens, about 0.01 lumens to about 10 lumens, about 0.005 lumens to about 5 lumens, about 0.05 lumens to about 5 lumens, about 0.1 lumens to about 5 lumens, about 0.2 lumens to about 1 lumens, or about 0.5 lumens to about 5 lumens.
The optical beam 10 incident on the sample S may have an area of about 0.5 to about 2 cm2, or about 1 cm2. Accordingly, the optical beam 10 incident on the sample S may have an irradiance within a range from about 0.1 mW/cm2 to about 100 mW/cm2, about 1 mW/cm2 to about 75 mW/cm2, about 1 mW/cm2 to about 50 mW/cm2, about 5 mW/cm2 to about 40 mW/cm2, about 5 mW/cm2 to about 30 mW/cm2, about 5 mW/cm2 to about 20 mW/cm2, or about 10 mW/cm2 to about 15 mW/cm2. The optical beam 10 incident on the sample S may have an illuminance (E) within a range from about 20 lux (lumens/m2) to about 100,000 lux, about 200 lux to about 75,000 lux, about 400 lux to about 50,000 lux, about 2,000 lux to about 25,000 lux, about 2,000 lux to about 15,000 lux, about 4,000 lux to about 15,000 lux, or about 4,000 lux to about 6,000 lux.
The light output of the visible portion of optical beam 10 may vary depending on the type of light source. In some cases, the visible light output of optical beam 10 may vary due to the different luminous efficacies of different types of light source. For example, blue light-emitting diode (LED) may have an efficacy of about 40 lumens/W, a red LED may have an efficacy of about 70 lumens/W, and a green LED may have an efficacy of about 90 lumens/W. Accordingly, the visible light output of optical beam 10 may vary depending on the color or wavelength range of the light source.
The light output of the visible portion of optical beam 10 may also vary due to the nature of interactions between the different components of a light source. For example, the light source may comprise a light source combined with an optical element configured to shift the wavelength of the light produced by the first light source, as described in further detail herein. In this embodiment, the visible light output of the visible portion of optical beam 10 may vary depending on the amount of the light produced by the light source that is configured to pass through the optical element without being absorbed or wavelength-shifted, as described in further detail herein.
As shown in
The visible aiming beam 20 may comprise light in the visible spectrum, for example in a range from about 390 nm to about 800 nm, which the user can see reflected on a portion of the sample material S. The aiming beam 20 can provide basic visual verification that the spectrometer 102 is operational, and can provide visual indication to the user that a measurement is in progress. The aiming beam 20 can help the user visualize the area of the sample material being measured, and thereby provide guidance the user in adjusting the position and/or angle of the spectrometer 102 to position the measurement area 50 over the desired area of the sample material S. The aiming beam 20 may be configured with circuitry to be emitted throughout the duration of a measurement, and automatically turn off when the measurement of the sample material S is complete; in this case, the aiming beam 20 can also provide visual indication to the user of how long the user should hold the spectrometer 102 pointed at the sample material S.
The visible aiming beam 20 and the measurement beam 30 may be produced by the same light source, wherein the visible aiming beam 20 comprises a portion of the measurement beam 30. Alternatively, the aiming beam 20 may be produced by a first light source, and the measurement beam 30 may be produced by a second light source. For example, the measurement beam 30 may comprise an infrared beam and the aiming beam 20 may comprise a visible light beam.
The measurement beam 30 may be configured to illuminate the measurement area 50 of the sample S, and the aiming beam 20 may be configured to illuminate an area of the sample overlapping with the measurement area, thereby displaying the measurement area to the user. The visible area illuminated by the visible aiming beam 20 may comprise from about 50% to about 150% or about 75% to about 125% of the measurement area, or at least about 90%, at least about 95%, or at least about 99% of the measurement area.
One or more optics of the illumination module, such as a lens or a parabolic reflector, may be arranged to receive the aiming beam 20 and the measurement beam 30 and direct the aiming beam and measurement beam toward the sample material S, with the aiming beam and measurement beam overlapping on the sample. The aiming beam 20 may be arranged to be directed along an aiming beam axis 25, while the measurement beam 30 may be arranged to be directed along a measurement beam axis 35. The aiming beam axis 25 may be co-axial with measurement beam axis 35.
The sensor or detector of the spectrometer module 160 may comprise one or more filters configured to transmit the measurement beam 30 but inhibit transmission of the aiming beam 20. In many configurations, the spectrometer module comprises one filter configured to inhibit transmission of visible light, thereby inhibiting transmission of portions of the aiming beam 20 and measurement beam 30 reflected from the sample that comprise visible light. In some configurations, the spectrometer module 160 may comprise a plurality of optical filters configured to inhibit transmission of a portion of the aiming beam 20 reflected the sample material S, and to transmit a portion of the measurement beam 30 reflected from the sample. In configurations of the spectrometer module comprising a plurality of optical channels, the spectrometer module may comprise a plurality of filters wherein each optical filter corresponds to an optical channel. Each filter may be configured to inhibit transmission of light within a specific range and/or within a specific angle of incidence, wherein the filtered specific range or specific angle of incidence may be specific to the corresponding channel. In some configurations, each optical channel of the spectrometer module may comprise a field of view. The field of view 40 of the spectrometer module may comprise a plurality of overlapping fields of view of a plurality of optical channels. The aiming beam and the measurement beam may overlap with the plurality of overlapping fields of view on the sample S. In many configurations, a diffuser may be disposed between the plurality of optical filters and the incident light from the sample, in which each optical filter corresponds to an optical channel. In such configurations, the plurality of optical channels may comprise similar fields of view through the diffuser, with each field of view at least partially overlapping with the fields of view of other optical channels. With the diffuser, the spectrometer may comprise a wide field of view, for example ±900.
Optionally, the visible aiming beam 20 may be produced by a light source separate from the illumination module 140. In this case, the separate light source may be configured to produce the aiming beam such that the aiming beam illuminates a portion of the sample material that overlaps with the measurement area 50 of the sample.
The compact size of the spectrometer 102 can provide a hand held device that can be directed (e.g., pointed) at a material to rapidly obtain information about the material. As shown in
The spectrometer can have a total volume of at most about 200 cm3, 150 cm3, 100 cm3, 95 cm3, 90 cm3, 85 cm3, 80 cm3, 75 cm3, 70 cm3, 65 cm3, 60 cm3, 55 cm3, 50 cm3, 45 cm3, 40 cm3, 35 cm3, 30 cm3, 25 cm3, 20 cm3, 15 cm3, 10 cm3, 5 cm3, or 1 cm3. The spectrometer can have a volume less than 1 cm3. The spectrometer can have a volume greater than 100 cm3. The spectrometer can have a volume that is between any of the two values given above. For example, the spectrometer may have a volume within a range from about 1 cm3 to about 200 cm3, about 40 cm3 to about 200 cm3, about 60 cm3 to about 150 cm3, about 80 cm3 to about 120 cm3, about 80 cm3 to about 100 cm3, or about 90 cm3.
The spectrometer shape can comprise a rectangular prism, cylinder, or other three-dimensional shape. The spectrometer can have a length of at most about 500 mm, 400 mm, 300 mm, 200 mm, 250 mm, 100 mm, 95 mm, 90 mm, 85 mm, 80 mm, 75 mm, 70 mm, 65 mm, 60 mm, 55 mm, 50 mm, 45 mm, 40 mm, 35 mm, 30 mm, 25 mm, 20 mm, 15 mm, 10 mm, or 5 mm. The spectrometer can have a length less than 5 mm. The spectrometer can have a length greater than 500 mm. The spectrometer can have a length that is between any of the two values given above. For example, the spectrometer have a length within a range from about 10 mm to about 100 mm, about 25 mm to about 75 mm, or about 50 mm to about 70 mm. The spectrometer can have a width of at most about 500 mm, 400 mm, 300 mm, 200 mm, 250 mm, 100 mm, 95 mm, 90 mm, 85 mm, 80 mm, 75 mm, 70 mm, 65 mm, 60 mm, 55 mm, 50 mm, 45 mm, 40 mm, 35 mm, 30 mm, 25 mm, 20 mm, 15 mm, 10 mm, or 5 mm. The spectrometer can have a width less than 5 mm. The spectrometer can have a width greater than 500 mm. The spectrometer can have a width that is between any of the two values given above. For example, the spectrometer may have a width within a range from about 10 mm to about 75 mm, about 20 mm to about 60 mm, or about 30 mm to about 50 mm. The spectrometer can have a height of at most about 500 mm, 400 mm, 300 mm, 200 mm, 250 mm, 100 mm, 95 mm, 90 mm, 85 mm, 80 mm, 75 mm, 70 mm, 65 mm, 60 mm, 55 mm, 50 mm, 45 mm, 40 mm, 35 mm, 30 mm, 25 mm, 20 mm, 15 mm, 10 mm, or 5 mm. The spectrometer can have a height less than 5 mm. The spectrometer can have a height greater than 500 mm. The spectrometer can have a height that is between any of the two values given above. For example, the spectrometer may have a height within a range from about 1 mm to about 50 mm, about 5 mm to about 40 mm, or about 10 mm to about 20 mm. The spectrometer may, for example, have dimensions within a range from about 0.1 cm×0.1 cm×2 cm to about 5 cm×5 cm×10 cm. In the case of a cylindrical spectrometer the spectrometer can have a radius of at most about 500 mm, 400 mm, 300 mm, 200 mm, 250 mm, 100 mm, 95 mm, 90 mm, 85 mm, 80 mm, 75 mm, 70 mm, 65 mm, 60 mm, 55 mm, 50 mm, 45 mm, 40 mm, 35 mm, 30 mm, 25 mm, 20 mm, 15 mm, 10 mm, or 5 mm. The spectrometer can have a radius less than 5 mm. The spectrometer can have a radius greater than 500 mm. The spectrometer can have a radius that is between any of the two values given above.
One or more of the components of the spectrometer can be powered by a battery. The battery can be on-board the spectrometer. The battery can have a weight of at most about 50 g, 45 g, 40 g, 35 g, 30 g, 25 g, 20 g, 15 g, 10 g, 5 g, 1 g, or 0.1 g. The battery can have a weight less than 0.1 g. The battery can have a weight greater than 50 g. The battery can have a weight that is between any of the two values given above. For example, the batter may have a weight that is within a range from about 2 g to about 6 g, about 3 g to about 5 g, or about 4 g.
The compact spectrometer 102 may have an optical resolution of less than 10 nm, less than 5 nm, less than 4 nm, less than 3 nm, less than 2 nm, less than 1 nm, less than 0.5 nm, or less than 0.1 nm. The spectrometer can have an optical resolution that is between any of the two values given above. For example, the spectrometer may have an optical resolution that is within a range from about 0.1 nm to about 100 nm, about 1 nm to about 50 nm, about 1 nm to about 10 nm, or about 2 nm to about 5 nm. The spectrometer may have an optical resolution of approximately 5 nm, which is equivalent to approximately 100 cm−1 at a wavelength of about 700 nm and equivalent to approximately 40 cm−1 at a wavelength of about 1100 nm. The spectrometer may have an optical resolution that is between 100 cm−1 and 40 cm−1. The spectrometer can have a temporal signal-to-noise ratio (SNR) of about 1000 for a single sensor reading (without averaging, at maximum spectral resolution) for a wavelength of about 1000 nm, or an SNR of about 2500 for a wavelength of about 850 nm. The compact spectrometer, when configured to perform algorithmic processing or correction of measured spectral data, may be able to detect changes in normalized signals in the order of about 1×10−3 to about 1×10−4, or about 5×10−4. The light source of the illumination module may be configured to have a stabilization time of less than 1 min, less than 1 s, less than 1 ms, or about 0 s.
Spectrometer Using Secondary Emission Illumination with Filter-Based Optics
Reference is now made to
The spectrometer system may comprise a plurality of optical filters of filter matrix 170. The optical filter can be of any type known in the art. Non-limiting examples of suitable optical filters include Fabry-Perot (FP) resonators, cascaded FP resonators, and interference filters. For example, a narrow bandpass filter (≤10 nm) with a wide blocking range outside of the transmission band (at least 200 nm) can be used. The center wavelength (CWL) of the filter can vary with the incident angle of the light impinging upon it.
The central wavelength of the central band can vary by 10 nm or more, such that the effective range of wavelengths passed with the filter is greater than the bandwidth of the filter. In many instances, the central wavelength varies by an amount greater than the bandwidth of the filter. For example, the bandpass filter can have a bandwidth of no more than 10 nm and the wavelength of the central band can vary by more than 10 nm across the field of view of the sensor.
The spectrometer system may comprise a filter matrix. The filter matrix can comprise one or more filters, for example a plurality of filters. The use of a single filter can limit the spectral range available to the spectrometer. A filter can be an element that only permits transmission of a light signal with a predetermined incident angle, polarization, wavelength, and/or other property. For example, if the angle of incidence of light is larger than 30°, the system may not produce a signal of sufficient intensity due to lens aberrations and the decrease in the efficiency of the detector at large angles. For an angular range of 30° and an optical filter center wavelength (CWL) of ˜850 nm, the spectral range available to the spectrometer can be about 35 nm, for example. As this range can be insufficient for some spectroscopy based applications, configurations with larger spectral ranges may comprise an optical filter matrix composed of a plurality of sub-filters. Each sub-filter can have a different CWL and thus covers a different part of the optical spectrum. The sub-filters can be configured in one or more of many ways and be tiled in two dimensions, for example.
Depending on the number of sub-filters, the wavelength range accessible to the spectrometer can reach hundreds of nanometers. In configurations comprising a plurality of sub-filters, the approximate Fourier transforms formed at the image plane (i.e. one per sub-filter) overlap, and the signal obtained at any particular pixel of the detector can result from a mixture of the different Fourier transforms.
The filter matrixes may be arranged in a specific order to inhibit cross talk on the detector of light emerging from different filters and to minimize the effect of stray light. For example, if the matrix is composed of 3×4 filters then there are 2 filters located at the interior of the matrix and 10 filters at the periphery of the matrix. The 2 filters at the interior can be selected to be those at the edges of the wavelength range. Without being bound by a particular theory, the selected inner filters may experience the most spatial cross-talk but be the least sensitive to cross-talk spectrally.
The spectrometer module may comprise a lens array 174. The lens array can comprise a plurality of lenses. The number of lenses in the plurality of lenses can be determined such that each filter of the filter array corresponds to a lens of the lens array. Alternatively or in combination, the number of lenses can be determined such that each channel through the support array corresponds to a lens of the lens array. Alternatively or in combination, the number of lenses can be selected such that each region of the plurality of regions of the image sensor corresponds to an optical channel and corresponding lens of the lens array and filter of the filter array.
The spectrometer system may comprise a detector 190, which may comprise an array of sensors. In many cases, the detector is capable of detecting light in the wavelength range of interest. The compact spectrometer system disclosed herein can be used from the UV to the IR, depending on the nature of the spectrum being obtained and the particular spectral properties of the sample being tested. The detector can be sensitive to one or more of ultraviolet wavelengths of light, visible wavelengths of light, or infrared wavelengths of light. In some cases, a detector that is capable of measuring intensity as a function of position (e.g. an array detector or a two-dimensional image sensor) is used.
In some instances the spectrometer does not comprise a cylindrical beam volume hologram (CVBH).
The detector can be located in a predetermined plane. The predetermined plane can be the focal plane of the lens array. Light of different wavelengths (X1, X2, X3, X4, etc.) can arrive at the detector as a series of substantially concentric circles of different radii proportional to the wavelength. The relationship between the wavelength and the radius of the corresponding circle may not be linear.
The detector may receive non-continuous spectra, for example spectra that can be unlike a dispersive element would create. The non-continuous spectra can be missing parts of the spectrum. The non-continuous spectrum can have the wavelengths of the spectra at least in part spatially out of order, for example. In some cases, first short wavelengths contact the detector near longer wavelengths, and second short wavelengths contact the detector at distances further away from the first short wavelengths than the longer wavelengths.
The detector may comprise a plurality of detector elements, such as pixels for example. Each detector element may be configured so as to receive signals of a broad spectral range. The spectral range received on a first and second pluralities of detector elements may extend at least from about 10 nm to about 400 nm. In many instances, spectral range received on the first and second pluralities of detector elements may extend at least from about 10 nm to about 700 nm. In many instances, spectral range received on the first and second pluralities of detector elements may extend at least from about 10 nm to about 1600 nm. In many instances, spectral range received on the first and second pluralities of detector elements may extend at least from about 400 nm to about 1600 nm. In many instances, spectral range received on the first and second pluralities of detector elements may extend at least from about 700 nm to about 1600 nm.
The spectrometer system may comprise a diffuser. In configurations in which the light emanating from the sample is not sufficiently diffuse, a diffuser can be placed in front of other elements of the spectrometer. The diffuser can be placed in a light path between a light emission and a detector and/or filter. Collimated (or partially collimated light) can impinge on the diffuser, which then produces diffuse light which then impinges on other aspects of the spectrometer, e.g. an optical filter.
In many cases, the lens array, the filter matrix, and the detector are not centered on a common optical axis. In many cases, the lens array, the filter matrix, and the detector are aligned on a common optical axis.
The principle of operation of compact spectrometer may comprise one or more of the following attributes. Light impinges upon the diffuser and at least a fraction of the light is transmitted through the diffuser. The light next impinges upon the filter matrix at a wide range of propagation angles and the spectrum of light passing through the sub-filters is angularly encoded. The angularly encoded light then passes through the lens array (e.g. Fourier transform focusing elements) which performs (approximately) a spatial Fourier transform of the angle-encoded light, transforming it into a spatially-encoded spectrum. Finally the light reaches the detector. The location of the detector element relative to the optical axis of a lens of the array corresponds to the wavelength of light, and the wavelength of light at a pixel location can be determined based on the location of the pixel relative to the optical axis of the lens of the array. The intensity of light recorded by the detector element such as a pixel as a function of position (e.g. pixel number or coordinate reference location) on the sensor corresponds to the resolved wavelengths of the light for that position.
In some cases, an additional filter is placed in front of the compact spectrometer system in order to block light outside of the spectral range of interest (i.e. to prevent unwanted light from reaching the detector).
In configurations in which the spectral range covered by the optical filters is insufficient, additional sub-filters with differing CWLs can be used.
In some instances, shutters allow for the inclusion or exclusion of light from part of the spectrometer 102. For example, shutters can be used to exclude particular sub-filters. Shutters may also be used to exclude individual lens.
The illumination module and the spectrometer module may be configured to have overlapping fields of view at the sample. The overlapping fields of view can be provided in one or more of many ways. For example, the optical axes of the illumination source, the temperature sensor and the matrix array can extend in a substantially parallel configuration. Alternatively, one or more of the optical axes can be oriented toward another optical axis of another module.
The temperature sensor can comprise a field of view (herein after “FoV”) limiter. In many instances, the temperature sensor has a field of view oriented to overlap with a field of view of the detector and a field of view of an illuminator. For example, the field of view can be limited by an aperture formed in a material supporting the window 132 of temperature sensor module and the dimensions of the temperature sensor 134. In some instances, the temperature sensor module has a limited field of view and comprises a heat conductive metal cage disposed on a flex printed circuit board (PCB) 136. The PCB 136 can be mounted on a stiffener 138 in order to inhibit movement relative to the other modules on the sensor head. The flexible circuit board may be backed by stiffener 138 comprising a metal. The temperature sensor 134 can be a remote temperature sensor. The temperature sensor can give a temperature that is accurate to within about 5, 4, 3, 2, 1, 0.7, 0.4, 0.3, 0.2 or 0.1 degree Celsius of the ambient temperature of the sample. The temperature sensor may measure the ambient temperature with precision to 3, 2, 1, 0.5, or 0.1 degree Celsius.
The spectrometer head may comprise an illumination module 140. The illumination module can illuminate a sample with light. In some instances, the illumination module comprises an illumination window 142. The illumination window can seal the illumination module. The illumination window can be substantially transmissive to the light produced in the illumination module. For example, the illumination window can comprise glass. The illumination module can comprise a light source 148. The light source can comprise one or more light emitting diodes (LED). For example, the light source may comprise a blue LED, red LED, green LED, infrared LED, or a combination thereof.
The light source 148 can be mounted on a mounting fixture 150. The mounting fixture may comprise a ceramic package. For example, the light fixture can be a flip-chip LED die mounted on a ceramic package. The mounting fixture 150 can be attached to a flexible printed circuit board (PCB) 152 which can optionally be mounted on a stiffener 154 to reduce movement of the illumination module. The flex PCB of the illumination module and the PCT of temperature sensor modules may comprise different portions of the same flex PCB, which may also comprise portions of spectrometer PCB.
The wavelength of the light produced by the light source 148 can be shifted by a plate 146. Plate 146 can be a wavelength shifting plate. Plate 146 may comprise phosphor embedded in glass. Alternatively or in combination, plate 146 can comprise a nano-crystal, a quantum dot, or combinations thereof. The plate can absorb light from the light source and release light having a frequency lower than the frequency of the absorbed light. In some cases, a light source produces visible light, and plate 146 absorbs the light and emits near infrared light. The light source may be in close proximity to or directly touching the plate 146. The light source and associated packaging may be separated from the plate by a gap to limit heat transfer. For example, the gap between the light source and the plate can be at least 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0 mm. Alternatively, the light source packaging may touch the plate 146 in order to conduct heat from the plate such that the light source packaging comprises a heat sink.
The illumination module can further comprise a light concentrator such as a parabolic concentrator 144 or a condenser lens in order to concentrate the light. The parabolic concentrator 144 may be a reflector. The parabolic concentrator 144 may comprise stainless steel or gold-plated stainless steel. The concentrator can concentrate light to a cone. For example, the light can be concentrated to a cone with a field of view of about 30-45, 25-50, or 20-55 degrees.
The illumination module may be configured to transmit light and the spectrometer module may be configured to receive light along optical paths extending substantially perpendicular to an entrance face of the spectrometer head. The modules can be configured such that light can be transmitted from one module to an object (such as a sample S) and reflected or scattered to another module which receives the light.
The optical axes of the illumination module and the spectrometer module may be configured to be non-parallel such that the optical axis representing the spectrometer module is at an offset angle to the optical axis of the illumination module. This non-parallel configuration can be provided in one or more of many ways. For example, one or more components can be supported on a common support and offset in relation to an optic such as a lens in order to orient one or more optical axes toward each other. Alternatively or in combination, a module can be angularly inclined with respect to another module. The optical axis of each module may be aligned at an offset angle of greater than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 25, 30, 35, 40, 45, or 50 degrees. The illumination module and the spectrometer module may be configured to be aligned at an offset angle of less than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 25, 30, 35, 40, 45, or 50 degrees. The illumination module and the spectrometer module can be configured to be aligned at an offset angle between than 1-10, 11-20, 21-30, 31-40 or 41-50 degrees. The offset angle of the modules may be set firmly and not adjustable, or the offset angle may adjustable. The offset angle of the modules may be automatically selected based on the distance of the spectrometer head from the sample. Two modules may have parallel optical axes. Two or more modules may have offset optical axes. In some instances, the modules can have optical axes offset such that they converge on a sample. The modules can have optical axes offset such that they converge at a set distance. For example, the modules can have optical axes offset such that they converge at a distance of about 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, or 500 mm away.
The first filter and the second filter can be arranged in one or more of many ways to provide a substantially uniform light distribution to the filters. The substantially uniform light distribution can be uniform with respect to an average energy to within about 25%, for example to within about 10%, for example. The first diffuser may distribute the incident light energy spatially on the second diffuser with a substantially uniform energy distribution profile. The first diffuser may make the light substantially homogenous with respect to angular distribution. The second diffuser can further diffuse the light energy of the substantially uniform energy distribution profile to a substantially uniform angular distribution profile, such that the light transmitted to each filter can be substantially homogenous both with respect to the spatial distribution profile and the angular distribution profile of the light energy incident on each filter. For example, the angular distribution profile of light energy onto each filter can be uniform to within about +/−25%, for example substantially uniform to within about +/−10%.
The spectrometer module comprises a filter matrix 170. The filter matrix can comprise one or more filters. In many instances, the filter matrix comprises a plurality of filters.
In some instances, each filter of the filter matrix 170 is configured to transmit a range of wavelengths distributed about a central wavelength. The range of wavelengths can be defined as a full width half maximum (hereinafter “FWHM”) of the distribution of transmitted wavelengths for a light beam transmitted substantially normal to the surface of the filter as will be understood by a person of ordinary skill in the art. A wavelength range can be defined by a central wavelength and by a spectral width. The central wavelength can be the mean wavelength of light transmitted through the filter, and the band spectral width of a filter can be the difference between the maximum and the minimum wavelength of light transmitted through the filter. Each filter of the plurality of filters may be configured to transmit a range of wavelengths different from other filters of the plurality. The range of wavelengths overlaps with ranges of said other filters of the plurality and wherein said each filter comprises a central wavelength different from said other filters of the plurality.
The filter array comprises a substrate having a thickness and a first side and a second side, the first side oriented toward the diffuser, the second side oriented toward the lens array. In some instances, each filter of the filter array comprises a substrate having a thickness and a first side and a second side, the first side oriented toward the diffuser, the second side oriented toward the lens array. The filter array can comprise one or more coatings on the first side, on the second side, or a combination thereof. Each filter of the filter array can comprise one or more coatings on the first side, on the second side, or a combination thereof. In some instances, each filter of the filter array comprises one or more coatings on the second side, oriented toward the lens array. In some instances, each filter of the filter array comprises one or more coatings on the second side, oriented toward the lens array and on the first side, oriented toward the diffuser. The one or more coatings on the second side can be an optical filter. For example, the one or more coatings can permit a wavelength range to selectively pass through the filter. Alternatively or in combination, the one or more coatings can be used to inhibit cross-talk among lenses of the array. In some instances, the plurality of coatings on the second side comprises a plurality of interference filters, said each of the plurality of interference filters on the second side configured to transmit a central wavelength of light to one lens of the plurality of lenses. In some instances, the filter array comprises one or more coatings on the first side of the filter array. The one or more coatings on the first side of the array can comprise a coating to balance mechanical stress. In some instances, the one or more coatings on the first side of the filter array comprises an optical filter. For example, the optical filter on the first side of the filter array can comprise an IR pass filter to selectively pass infrared light. In many instances, the first side does not comprise a bandpass interference filter coating. In some instances, the first does not comprise a coating.
In many instances, the array of filters comprises a plurality of bandpass interference filters on the second side of the array. The placement of the fine frequency resolving filters on the second side oriented toward the lens array and apertures can inhibit cross-talk among the filters and related noise among the filters. In many instances, the array of filters comprises a plurality of bandpass interference filters on the second side of the array, and does not comprise a bandpass interference filter on the first side of the array.
In many instances, each filter defines an optical channel of the spectrometer. The optical channel can extend from the filter through an aperture and a lens of the array to a region of the sensor array. The plurality of parallel optical channels can provide increased resolution with decreased optical path length.
The spectrometer module can comprise an aperture array 172. The aperture array can prevent cross talk between the filters. The aperture array comprises a plurality of apertures formed in a non-optically transmissive material. In some instances, the plurality of apertures is dimensioned to define a clear lens aperture of each lens of the array, wherein the clear lens aperture of each lens is limited to one filter of the array. In some instances, the clear lens aperture of each lens is limited to one filter of the array.
In many instances the spectrometer module comprises a lens array 174. The lens array can comprise a plurality of lenses. The number of lenses can be determined such that each filter of the filter array corresponds to a lens of the lens array. Alternatively or in combination, the number of lenses can be determined such that each channel through the support array corresponds to a lens of the lens array. Alternatively or in combination, the number of lenses can be selected such that each region of the plurality of regions of the image sensor corresponds to an optical channel and corresponding lens of the lens array and filter of the filter array.
In many instances, each lens of the lens array comprises one or more aspheric surfaces, such that each lens of the lens array comprises an aspherical lens. In many instances, each lens of the lens array comprises two aspheric surfaces. Alternatively or in combination, one or more individual lens of the lens array can have two curved optical surfaces wherein both optical surfaces are substantially convex. Alternatively or in combination, the lenses of the lens array may comprise one or more diffractive optical surfaces.
In many instances, the spectrometer module comprises a support array 176. The support array 176 comprises a plurality of channels 177 defined with a plurality of support structures 179 such as interconnecting annuli. The plurality of channels 177 may define optical channels of the spectrometer. The support structures 179 can comprises stiffness to add rigidity to the support array 176. The support array may comprise a stopper to limit movement and fix the position the lens array in relation to the sensor array. The support array 176 can be configured to support the lens array 174 and fix the distance from the lens array to the sensor array in order to fix the distance between the lens array and the sensor array at the focal length of the lenses of the lens array. In many instances, the lenses of the array comprise substantially the same focal length such that the lens array and the sensor array are arranged in a substantially parallel configuration.
The support array 176 can extend between the lens array 174 and the stopper mounting 178. The support array 176 can serve one or more purposes, such as 1) providing the correct separation distance between each lens of lens array 170 and each region of the plurality of regions of the image sensor 190, and/or 2) preventing stray light from entering or exiting each channel, for example. In some instances, the height of each support in support array 176 is calibrated to the focal length of the lens within lens array 174 that it supports. In some instances, the support array 176 is constructed from a material that does not permit light to pass such as substantially opaque plastic. In some instances, support array 176 is black, or comprises a black coating to further reduce cross talk between channels. The spectrometer module can further comprise a stopper mounting 178 to support the support array. In many instances, the support array comprises an absorbing and/or diffusive material to reduce stray light, for example.
In many instances, the support array 176 comprises a plurality of channels having the optical channels of the filters and lenses extending therethrough. In some instances, the support array comprise a single piece of material extending from the lens array to the detector (i.e. CCD or CMOS array).
The lens array can be directly attached to the aperture array 172, or can be separated by an air gap of at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 30, 40, or 50 micrometers. The lens array can be directly on top of the support array 178. Alternatively or in combination, the lens array can be positioned such that each lens is substantially aligned with a single support stopper or a single optical isolator in order to isolate the optical channels and inhibit cross-talk. In some instances, the lens array is positioned to be at a distance approximately equal to the focal length of the lens away from the image sensor, such that light coming from each lens is substantially focused on the image sensor.
In some instances, the spectrometer module comprises an image sensor 190. The image sensor can be a light detector. For example, the image sensor can be a CCD or 2D CMOS or other sensor, for example. The detector can comprise a plurality of regions, each region of said plurality of regions comprising multiple sensors. For example, a detector can be made up of multiple regions, wherein each region is a set of pixels of a 2D CMOS. The detector, or image sensor 190, can be positioned such that each region of the plurality of regions is directly beneath a different channel of support array 176. In many instances, an isolated light path is established from a single of filter of filter array 170 to a single aperture of aperture array 172 to a single lens of lens array 174 to a single stopper channel of support array 176 to a single region of the plurality of regions of image sensor 190. Similarly, a parallel light path can be established for each filter of the filter array 170, such that there are an equal number of parallel (non-intersecting) light paths as there are filters in filter array 170.
The image sensor 190 can be mounted on a flexible printed circuit board (PCB) 184. The PCB 184 can be attached to a stiffener 186. In some instances, the stiffener comprises a metal stiffener to prevent motion of the spectrometer module relative to the spectrometer head 120.
The glass-embedded phosphor of plate 146 may be a near-infrared (NIR) phosphor, capable of emitting infrared or NIR radiation in the range from about 700 nm to about 1100 nm.
The light filter 188 may be configured to block at least a portion of visible radiation included in the incident light.
In some cases, the first wavelength range of the first filter and the second wavelength range of the second filter fall within a wavelength range of about 400 nm to about 1100 nm. In some instances, the second wavelength range overlaps the first wavelength range by at least 2% of the second wavelength range. In some instances, the second wavelength range overlaps the first wavelength range by an amount of about 1% to about 5% of the second wavelength range. The overlap in the range of wavelengths of the filters may be configured to provide algorithmic correction of the gains across different channels, for example across the outputs of a first filter element and a second filter element.
The coating of the filter array and/or the support array may comprise a black coating configured to absorb most of the light that hits the coated surface. For example, the coating may comprise a coating commercially available from Anoplate (as described on http://www.anoplate.com/capabilities/anoblack_ni.html), Acktar (as described on the world wide web at the Acktar website, www.acktar.com), or Avian Technologies (as described on http://www.aviantechnologies.com/products/coatings/diffuse_black.php), or other comparable coatings.
The stopper and the image sensor may be configured to have matching coefficients of thermal expansion (CTE). For example, the stopper and the image sensor may be configured to have a matching CTE of about 7 10−6 K−1. In order to match the CTE between the stopper and the image sensor where the stopper and image sensor have different CTEs, a liquid crystal polymer, such as Vectra E130, may be applied between the stopper and the image sensor.
The lens may be configured to introduce some distortion in the output of the lens, in order to improve performance in analyzing the obtained spectral data. The filters described herein may typically allow transmission of a specific wavelength for a specific angle of propagation of the incident light beam. As the light transmitted through the filters pass through the lens, the output of the lens may generate concentric rings on the sensor for different wavelengths of incident light. With typical spherical lens performance, as the angle of incidence grows larger, the concentric ring for that wavelength becomes much thinner (for a typical light bandwidth of ˜5 nm). Such variance in the thickness of the rings may cause reduced linearity and related performance in analyzing the spectral data. To overcome this non-linearity, some distortion may be introduced into the lens, so as to reduce the thickness of the rings that correspond to incident light having smaller angles of propagation, and increase the thickness of the rings that correspond to incident light having larger angles of propagation, wherein non-linearity of ring size related to incident angle is decreased. Lenses configured to produce such distortion in the output can produce a more even distribution of ring thicknesses along the supported range of angles of incidence, consequently improving performance in the analysis of the generated spectral data. The distortion can be provided with one or more aspheric lens profiles to increase the depth of field (DoF) and increase the size of the point spread function (PSF) as described herein.
Referring again to
The power or visible light output of the aiming beam 20 may vary depending on the amount of optical beam 10 that is configured to pass through the plate 146 without being absorbed or wavelength-shifted. About 0.1% to about 10%, about 0.5% to about 5%, about 1% to about 4%, or about 2% to about 3% of optical beam 10 may be transmitted through plate 146 without being wavelength-shifted. The transmission of the optical beam 10 through plate 146 may be affected by the thickness of the plate 146. Further, the transmission of the optical beam 10 through plate 146 may be affected by the type of light source 148. For example, different types of light sources can be absorbed by the plate 146 at different efficiencies, consequently affecting the amount of light that is transmitted through the plate 146 without being wavelength-shifted. For a light source 148 comprising a blue LED and a plate 146 comprising phosphor-embedded glass, about 10 mW to about 15 mW (or about 0.4 to about 0.6 lumens) of light may transmit through the plate 146 to form the aiming beam 20. By comparison, light produced by a light source comprising a red LED may not absorb as efficiently by a phosphor-embedded glass plate, and consequently more light, for example about 15 mW to about 30 mW (or about 1 to about 2 lumens) of the light, may transmit through the plate to form the aiming beam 20.
The spectrometer module 160 may comprise one or more filters configured to transmit the measurement beam 30 but inhibit transmission of the aiming beam 20. In many configurations, the spectrometer module comprises one filter, such as light filter 188, configured to inhibit transmission of visible light, thereby inhibiting transmission of portions of the aiming beam 20 and measurement beam 30 reflected from the sample that comprise visible light. In some configurations, the spectrometer module may comprise a plurality of optical filters configured to inhibit transmission of a portion of the aiming beam 20 reflected the sample material S, and to transmit a portion of the measurement beam 30 reflected from the sample. For example, the plurality of optical filters may comprise the optical filters of the filter matrix 170, wherein each filter in the filter matrix 170 corresponds to an optical channel of the plurality of channels 177. Each filter may be configured to inhibit transmission of light within a specific range and/or within a specific angle of incidence, wherein the filtered specific range or specific angle of incidence may be specific to the corresponding channel. In some configurations, each optical channel may comprise a field of view. The field of view of the spectrometer module 160 may hence comprise a plurality of overlapping fields of view of the plurality of optical channels 177. The aiming beam 20 and the measurement beam 30 may overlap with the plurality of overlapping fields of view on the sample S.
Spectrometer Using Multiple Illumination Sources
The illumination module 140 comprises at least two light sources, such as light-emitting diodes (LEDs) 210. The illumination module may comprise at least about 10 LEDs. The illumination module 140 further comprises a radiation diffusion unit 213 configured to receive the radiation emitted from the array of LEDs 210, and provide as an output illumination radiation for use in analyzing a sample material. The radiation diffusion unit may comprise one or more of a first diffuser 215, a second diffuser 220, and one lens 225 disposed between the first and second diffusers. The radiation diffusion unit may further comprise additional diffusers and lenses. The radiation diffusion unit may comprise a housing 214 to support the first diffuser and the second diffuser with fixed distances from the light sources. The inner surface of the housing 214 may comprise a plurality of light absorbing structures 216 to inhibit reflection of light from an inner surface of the housing. For example, the plurality of light absorbing structures may comprise one or more of a plurality of baffles or a plurality of threads, as shown in
The array of LEDs 210 may be configured to generate illumination light composed of multiple wavelengths. Each LED may be configured to emit radiation within a specific wavelength range, wherein the wavelength ranges of the plurality of LEDs may be different. The LEDs may have different specific power, peak wavelength and bandwidth, such that the array of LEDs generates illumination that spans across the spectrum of interest. There can be between a few LEDs and a few tens of LEDs in a single array.
In some instances, the LED array is placed on a printed circuit board (PCB) 152. In order to reduce the size, cost and complexity of the PCB and LED driving electronics and reduce the number of interconnect lines, the LEDs may preferably be arranged in rows and columns, as shown in
The LED currents can be regulated by various means as known to those skilled in the art. In some instances, Current Control Regulator (CCR) components may be used in series to each anode row and/or to each cathode column of the array. In some instances, a current control loop may be used instead of the CCR, providing more flexibility and feedback on the actual electrode currents. Alternatively, the current may be determined by the applied anode voltages, though this method should be used with care as LEDs can vary significantly in their current to voltage characteristics.
An optional voltage adjustment diode can be useful in reducing the difference between the LED driving voltages of LEDs sharing the same anode row, so that they can be driven directly from the voltage source without requiring a current control circuit. The optional voltage adjustment diode can also help to improve the stability and simplicity of the driving circuit. These voltage adjustment diodes may be selected according to the LEDs' expected voltage drops across the row, in opposite tendency, so that the total voltage drop variation along a shared row is smaller.
Referring to
The first diffuser 215, preferably mechanically supported and protected by a cover glass 230, may be placed above the array of LEDs 210. The diffuser may be configured to equalize the beam patterns of the different LEDs, as the LEDs will typically differ in their illumination profiles. Regardless of the beam shape of any LED, the light that passes through the first diffuser 215 can be configured to have a Lambertian beam profile, such that the emitted spectrum at each of the directions from first diffuser 215 is uniform. Ideally, the ratios between the illuminations at different wavelengths do not depend on the direction to the plane of the first diffuser 215, as observed from infinity. Such directions are indicated schematically by the dashed lines shown in
The first diffuser 215 is preferably placed at the aperture plane of the lens 225. Thus, parallel rays can be focused by the lens to the same location on the focal plane of the lens, where the second diffuser 220 is placed (preferably supported and protected by cover glass 230). Since all illumination directions at the output of the first diffuser 215 have the same spectrum, the spectrum at the input plane of the second diffuser 220 can be uniform (though the absolute power may vary). The second diffuser 220 can then equalize the beam profiles from each of the locations in its plane, so that the output spectrum is uniform both in location and in direction, leading to uniform spectral illumination across the sample irrespective of the sample distance from the device (when the sample is close to the device it is more affected by the spatial variance of spectrum, and when the sample is far from the device it is more affected by the angular variation of the spectrum).
In designing the radiation diffusion unit 213 configured to improve spectral uniformity, size and power may be traded off in order to achieve the required spectral uniformity. For example, as shown in
Referring back to
The one or more photodiodes 263 are preferably placed at the focal plane of lens 225, as shown in
The photodiode current can be detected using a trans-impedance amplifier. For the dual photodiode architecture embodiment, the photocurrent can first be converted from current to voltage using resistors with resistivity that provides high gain on the one hand to reduce noise, while having a wide enough bandwidth and no saturation on the other hand. An operational amplifier can be connected in photovoltaic mode amplification to the photodiodes, for minimum noise. Voltage dividers can provide a small bias to the operational amplifier (Op Amp) to compensate for possible bias current and bias voltage at the Op Amp input. Additional amplification may be preferable with voltage amplifiers.
In the embodiment of the spectrometer head shown in
In some instances, the modulation/demodulation may be achieved by time division multiplexing (TDM). In TDM, each LED is switched “on” in a dedicated time slot, and the photocurrent sampled in synchronization to that time slot represents the contribution of the corresponding LED and its wavelength. Black level and ambient light is measured at the “off” times between “on” times.
In some instances, the modulation/demodulation may be achieved by frequency division modulation (FDM). In FDM, each LED is modulated at a different frequency. This modulation can be with any waveform, and preferably by square wave modulation for best efficiency and simplicity of the driving circuit. This means that at any given time, one or more of the LEDs can be “on” at the same time, and one of more of the LEDs can be “off” at the same time. The detected signal is decomposed to the different LED contributions, for example by using matched filter or fast Fourier transform (FFT), as known to those skilled in the art.
FDM may be preferable with respect to TDM as FDM can provide lower peak current than TDM for the same average power, thus improving the efficiency of the LEDs. The higher efficiency allows for lower LED temperatures, which in turn provide better LED spectrum stability. Another advantage of FDM is that FDM has lower electromagnetic interference than TDM (since slower current slopes can be used), and smaller amplification channel bandwidth requirement than TDM.
In some instances, the modulation/demodulation may be achieved by amplitude modulation, each at a different frequency.
When the LED array uses a shared-electrodes architecture, a single LED can be turned “on” when the corresponding row and column are connected (e.g., anode to power and cathode to GND). However, when more than one row and one column is switched “on”, all the LEDs sharing the connected rows and columns will be switched on. This can complicate the modulation/demodulation scheme. In order to resolve such a complication, TDM may be used, wherein a single row and a single column is enabled at each “on” time slot. Alternatively, combined TDM and FDM may be used, wherein a single row is selected with TDM, and FDM is applied on the columns (or vice versa). Alternatively, a 2-level FDM may be used, wherein each row and each column is modulated at different frequencies. The LEDs can be decoupled using matched filter or spectrum analysis, while taking special care to avoid overlapping harmonics of base frequencies.
Referring again to
Additional Disclosure Relating to Spectrometer Using Secondary Emission Illumination with Filter-Based Optics
The coated side 173 of the filter array 170 and the aperture array 172 may be configured to have as small a gap 169 as possible. In preferred embodiments, the gap is substantially zero, such that the coated side of the filter array is in contact with the aperture array. The elements of the optical subassembly 165 may be designed such that the position of the filter array 170 along the optical axis (Z-axis) is determined by the thickness of the lens array 174 and the aperture array 172, such that the filter array physically contacts the lens array, and the subassembly comprising the filter array, lens array, and aperture array can be bonded to the support array 176.
The spaces 171 between the filters of the filter array 170 can be filled with an index-matched material to enable homogeneous illumination at the plane of the coated side 173 of the filter array. This can accomplished, for example, using an optical adhesive 167 that can also encapsulate and thereby provide structural support to the filter array. The optical adhesive 167 may be optically clear and comprise an index of refraction similar to the substrate material of the filter array 170 (e.g., fused glass). The optical adhesive 167 may comprise one or more of a variety of chemicals such as silicone and epoxy, and may be cured using one or more curing mechanisms known in the art, such as UV-curing.
Preferably, the positions of the filter array 170, aperture array 172, and lens array 174 are tightly controlled, so as to reduce chipping and peeling of the filter coating at the edges of the filters, and to minimize the necessary filter area in order to reduce cost. For example, the positions of the filter array, aperture array, and lens array may be substantially fixed relative to one another. The support array 176 may be configured to align the lens array, the aperture array, and the filter array, for example.
The filter array 170 can be configured to have top and bottom surfaces that are parallel to one another, such that the filter array can support the assembly of additional elements of the spectrometer module (e.g., referring again to
Alternatively, in embodiments comprising a filter array 170 having filters of uniform thickness, the optical subassembly 165 may be assembled such that the filter array 170 is in direct contact with the glass plate 168. For example, the top surface of the filter array may be placed flush against the bottom surface of the glass plate. Such an assembly configuration can eliminate the need to bond the filter array to the aperture array 172, since the filter array can be retained in a substantially fixed position by the glass plate 168. Without the need to support bonding of the filter array, the aperture array can be simplified in construction and/or have fewer constraints on design. For example, the aperture array can be made without the grooves 175, and/or be made from a more flexible material.
Filter Coatings
Referring again to
It is helpful when the intensity of light in each ring, corresponding to light of a particular wavelength, is affected by the intensity of illumination at that wavelength on diffuser 164, but does not depend on the position of the illumination on the diffuser 164. In order to reduce the dependence of measured light intensity on the position of the light hitting the diffuser, the diffuser 164 may be placed at the aperture plane of the lens array 174. Placing the diffuser farther from the lens aperture plane may result in variations in the spatial distribution of light on the diffuser, translating into variations in the intensity distribution in the ring images on the image sensor 190. Such an effect can decrease the accuracy of the spectrometer.
To reduce the system's sensitivity to the spatial distribution of light on the diffuser, the lens array 174 may be configured to account for the thickness of the interference filter substrate, such that the aperture plane of the lens of the array is one or more of near, adjacent or coincides with the plane of the diffuser The entrance pupil defined with aperture plane may comprise a virtual plane that coincides with the plane of the diffuser, for example with a lens comprising a plurality of components such as a multicomponent lens. The aperture plane can be physically located between each of a plurality of lens components such that the entrance pupil of the lens coincides with the plane of the diffuser, for example. Alternatively or in combination, the substrate of the filter may comprise a diffusing material such as an opal glass, for example which can place the diffuser near to the aperture, for example adjacent or coinciding with the apertures.
Alternatively or in combination, to reduce the system's sensitivity to the spatial distribution of light on the diffuser, the functions of the diffuser and filter may be combined.
Referring again to
To further simplify the design and production of the spectrometer, a bulk visible light filter, such as light filter 188 of
The optical elements shown in the configurations of
In configurations with an optical component comprising an interference filter coated on a substrate with a diffuser, such as the configurations shown in
The surface of the substrate supporting the filter coating may comprise an optically flat surface. As used herein an optically flat surface encompasses having a wavelength to root mean square (RMS) ratio that is surface sufficiently small, such as having an RMS of no more than one or more of lambda (λ) over 5 (λ/5), lambda (λ) over 10 (λ/10), for example. The specified wavelength lambda (λ) may comprise one or more of the shortest wavelength measured with the spectrometer, longest wavelength measured with the spectrometer, or an average wavelength measured with the spectrometer.
Each of the components shown in
The lenses 335 can be an array of refractive lithographic lenses grown at the uncoated side of the substrate before the substrate is cut into individual filter assemblies. Alternatively or in combination, the lenses can be an array of Fresnel lenses, either etched into the optical substrate before the substrate is cut into individual filter assemblies, or built separately from a thin plate, adhered to the optical substrate, and cut together with the substrate into individual filter assemblies, as in wafer level packaging techniques. Other methods may be used for building lenses onto the optical substrate, as known in the art. For example, techniques commonly used in the optical wafer-level industry, such as using drops of glue with well controlled volumes to build the lenses, may be used. The lenses can be configured such that the diffuser is placed at the entrance pupil defined with aperture plane of the lens.
Lenses that are attached to or built directly onto the filter substrate are not limited to the configuration of
The aperture array 172 as shown in
An aperture array comprising a plurality of apertures having different sizes can be advantageous in controlling the balance between the intensities of light collected by the different channels in the filter array. Different channels of the filter array may provide light to the filter array with different throughput, due to factors such as the illumination spectrum intensity, image sensor spectral response curve, and spectrometer system geometry. The balancing of the spectral illumination intensity with the transmission efficiency of the filters can provide a more uniform amount of intensity on the detector elements for an object with a uniform spectral response, e.g. white, in order to increase the signal to noise ratio of the spectrometer. A channel with one or more of a relatively lower light intensity or a relatively lower transmission efficiency may be provided with an aperture of a relatively larger size, such that the intensity of the illumination of the detector can be increased. A channel with one or more of a relatively higher light intensity or a relatively higher transmission efficiency may be provided with an aperture of a relatively smaller size, such that the intensity of the illumination on the detector array can be decreased. This balancing of the intensities of different channels using apertures of different sizes, the light intensity detected by the lower optical throughput channels may be increased without saturating the signal detected by the higher-efficiency channels. The light intensity detected by the relatively higher optical throughput channels may be decreased without decreasing the signal detected by the relatively lower optical throughput channels. Balancing the intensities of different channels can also help to balance cross-channel disturbances, so that disturbances or cross-talk between the different channels can be better compensated.
Modulated Light Beam
When performing spectroscopy in ambient lighting conditions, the reduction of noise, such as that from ambient light impingent on the detector can be helpful. An approach suitable for reduction of noise is to record a “dark frame,” comprising a signal taken with the optical beam turned off, in addition to a “probe frame,” comprising an signal taken with the optical beam turned on. The dark frame represents a recording of the portion of the signal illumination that is due to external sources, such as ambient light. By subtracting the dark frame from the probe frame, a signal showing the net effect of the optical beam can be isolated.
This approach can reduce noise but may not account for changes in ambient light intensity or pattern over time in some instances. For example, if a probe frame is recorded followed by a dark frame, the dark frame is supposed to represent the ambient light at the time the probe frame was taken, but is a measurement of the ambient light some time later. If the ambient light changed in intensity or pattern during that time, the dark frame will fail to properly account for it, resulting in a higher level of noise.
In some examples, to account for the possibility of changes in ambient lighting and other sources of noise, more than one dark frame may be recorded. For example, two dark frames may be recorded, one before and one after a probe frame. The average of the two dark frames will then be a more accurate approximation of the “true” dark frame that would have been recorded during the probe frame, had the probe light not been turned on. In further examples, a plurality of dark frames may be recorded and used to determine a trend in ambient noise, for example by fitting with a polynomial curve or other suitable function. While this method of noise reduction will typically lead to greater accuracy with greater number of dark frames, it also may lead to inefficient amounts of data acquisition and processing.
Modulation effects of the light beam can be used to filter out noise from ambient sources. By modulating the probe beam at a known frequency, then demodulating the recorded signal using the same frequency as a reference, noise can be reduced. However, the choice of modulation frequency is helpful. Noise sources that vary at frequencies close to or the same as the chosen modulation frequency may provide less than ideal results. Thus, if a modulation frequency is chosen that matches the characteristic frequency of some ambient source, demodulation may fail to effectively eliminate that noise.
The light source may be configured to provide the modulated optical beam incident on the sample with an illuminance (Ev) of no more than about 100,000 lux (lm/m2), or within a range from about 20 lux (lm/m2) to about 100,000 lux (lm/m2). The light source may be configured to provide the modulated optical beam incident on the sample with an irradiance of no more than about 100 mW/cm2, or within a range from about 0.1 mW/cm2 to about 100 mW/cm2.
In step 2201, a noise spectrum is determined. This determination may be made by performing a Fourier transform on a plurality of sequential dark frames. An FFT may be used to generate a noise spectrum in this manner. The frequency resolution of this measurement will be proportional to the number of frames used to generate it; for this reason, it may be desired to record a large number of frames. The noise spectrum may in some cases identify pixel-by-pixel noise spectra, and may in some cases identify noise spectra averaged over a plurality of pixels, including for example all pixels. Further implementations may record data at only a small number of pixels to increase the speed at which frames may be recorded. Alternatively or in combination, the ambient noise spectrum may be generated using measurements from an independent sensor. The noise spectrum generated by step 2201 may relate measured noise as a function of frequency, for example as depicted in
In step 2202, one or more frequency bands are identified in which noise is relatively low. These bands may correspond to local minima in the noise spectrum, as can be found for example by a peak finding algorithm. In some cases, the frequency bands may be identified by finding local maxima in the measured noise, then choosing frequencies that are at least a minimum desired distance away from the noise maxima in order to substantially decrease noise. In many cases, it may be preferred to choose a frequency high enough to avoid 1/f noise, and this may be accomplished in many ways, such as designating a band of low frequencies as undesirable, or by weighting a plurality of candidate frequency bands to favor those at higher frequencies. In some cases, certain frequencies may be pre-designated as undesirable; for example, frequencies near certain multiples of 50 or 60 Hz may be designated as undesirable to avoid electronic or light noise due to AC power sources.
In step 2203, a modulation frequency is chosen from one of the identified bands. This choice may be made on a variety of bases, such as choosing the global minimum of noise, or choosing the maximum distance from noise maxima, or choosing among a set of local minima, for example. The chosen frequency may further comprise a set of chosen frequencies, which may be useful, for example, when multiple light sources are to be modulated at different frequencies. When choosing more than one frequency, the chosen frequencies may be selected from a set of frequencies within one band, of from more than one band, and the differences in frequencies may be adjusted to improve accuracy in future demodulation.
In step 2204, the chosen frequencies are assigned to be used in modulation. This assignment may be performed automatically by setting a variable modulation frequency to a chosen frequency, and may in some cases involve an optional user confirmation. This step may also be performed by defining a fixed set of frequencies for future use, for example in the process of manufacturing the spectrometer.
In step 2205, the one or more chosen frequencies are used to modulate one or more light sources, for example, in Frequency Division Modulation. By recording images or other sensor data taken during light modulation, then demodulating the recorded data, detected signals may be retrieved, allowing each light source to be identified by its corresponding frequency. When multiple different light sources are used, such as a plurality of LEDs, each light source may be modulated at a different frequency. In some cases, the different frequencies may be selected from separate bands, and in some cases one or more frequencies may be selected from the same band.
In step 2206, the user directs the spectrometer at a sample. This allows the modulated light sources to illuminate the sample.
In step 2207, the user directs the detector of the spectrometer to view the illuminated sample. This step may include the user confirming that the modulated light sources are illuminating the correct portion of the sample, as well as confirming that the sample is within the field of view of the detector.
In step 2208, the spectrometer records signals such as images to measure the light scattered from the sample. In some cases, this measurement will comprise a plurality of signals. Data representing these signals may be stored in memory for processing, processed on-the-fly, or processed remotely as described herein.
In step 2209, the associated processor processes the measured light. This step may include one or more demodulation steps for each modulation frequency, to recover a spectrum corresponding to each modulated light source while eliminating noise. This may alternatively or additionally include a step of subtracting a recorded dark frame, or a combination of multiple dark frames, from one or more recorded signals. This step allows the isolation of one or more signals corresponding to one or more light frequencies.
In step 2210, one or more spectra are determined from the signals isolated in step 2209. These spectra may correspond to measured powers at one or more frequencies of emitted and/or scattered light. In some cases, the spectra may be corrected for the relative strengths of different illuminating beams; for example, the amplitudes corresponding to each of a plurality of light sources may be divided by the intensities of each respective light source, then combined to create a normalized spectrum.
Another method of modulation that may alternatively or additionally be employed involves spatial recording of modulation data. In sensors such as CMOS sensors comprising a rolling shutter architecture, the rolling shutter may be exploited to allow modulation at frequencies much higher than the sensor frame rate. Because a rolling shutter exposes different pixel columns to incident light at different times, a single frame such as an image frame may comprise a spatial encoding of time information.
Each pixel column may then be treated as an independent frame measurement, separated by an amount of time given by the rate at which the shutter exposes pixels. A spatial Fourier transform along the direction of shutter movement may then be used to extract frequency information, giving a column of frequency spectra, one for each row of pixels. When performed on one or more dark frames, this sequence of measurements may then be used in conjunction with method 2200 to achieve a noise spectrum at higher frequencies and/or with fewer frames recorded. Similarly, use of a rolling shutter in conjunction with a probe beam may allow spectroscopy to be performed with high modulation frequency, due to the high effective frame rate. Because rolling shutter measurements encode temporal data spatially, light with substantial spatial inhomogeneity may give rise in some cases to false frequency measurements. For this reason, rolling shutter measurements is most useful in situations where incident light is more spatially uniform.
Support Array
Referring again to
The spectrometer can be configured to inhibit cross-talk. Referring again to
In the example shown in
Increasing the area of the imaging portion of each sensor area can have important advantages for a compact spectrometer as described herein. For example, larger imaging portions can allow light of higher angles of incidence to be detected by the image sensor, thus extending the spectral range covered by each optical channel. However, in configurations as described wherein the channel walls do not extend all the way to the image sensor, the size of each imaging portion of a sensor area can be limited by the crosstalk between channels. For example, in the configuration shown in
To increase the area of imaging portions of an image sensor without increasing crosstalk between optical channels, a support array may be configured such that the channel walls extend all the way to the image sensor.
Alternatively to or in combination with extending the channel walls all the way to the image sensor, a support array may be modified in shape to further increase the size of the imaging portions of the image sensor. As described herein, each channel of a support array may comprise a first opening adjacent the lens array, a second opening adjacent the image sensor, and a channel wall extending between the first opening and the second opening. Both the first opening 1771 and the second opening 1772 of each channel 177 may be round or substantially circular in shape, thereby defining a substantially cylindrical channel therebetween, for example as shown with reference
While the spectrometer can be configured in many ways, the filter and lens array as described herein can be configured to provide an annular spectral pattern 2500 on each rectangular sensor area. For example, the filters many comprise interference filters with coatings or etalons and combinations thereof. The annular spectral pattern may comprise annular variations in intensity 2510 corresponding to spectral lines of the spectrum from the object. The annular patterns may comprise segments 2520 extending into the corner portions of imaging portion 1903b of each sensor area. These annular segments provide additional spectral data and information that can increase the resolution of the spectrometer. The processor coupled to the detector can be configured to receive the spectral data from the corner portions. The processor as described herein can be configured to measure the spectrum of the object in response to the annular segments extending into the corner portions of the imaging portions. The processor may comprise a remote processor such as a cloud based server, for example.
Lateral Diffuser
Referring again to
Sources of geometrical deviations may include, for example: 1) Differences in distances between various portions of the sample and the integrated light source of the spectrometer, combined with differences in distances between the illuminated portions of the sample and different locations of the spectrometer input port (differences in distances between various portions of the sample and the light source lead to uneven illumination of the sample surface, especially as the distance between the sample surface and the light source decreases; differences in distances between illuminated portions of the sample and the spectrometer input port leads to uneven distribution of input light intensity across the input port, especially as the distance between the sample surface and the light source decreases); 2) Uneven reflection of light from sample may cause uneven spread of light across the front surface of the spectrometer input port; 3) Measuring a sample while holding the spectrometer tilted with respect to the sample surface; 4) Dirt and particles on the outside surface of the spectrometer input port, blocking some of the incoming light with a non-uniform geometrical distribution; 5) Uneven illumination when using the device with various accessories. One or more of these reasons, in addition to various other reasons not listed, may result in geometrical deviations of light incident on the spectrometer input port.
Disclosed herein are methods and devices for spatially spreading the incoming sample light before the light reaches the optical detector of the spectrometer, to improve the uniformity of the spatial distribution of light on the detector. For example, the methods and devices can spatially distribute the light from the sample substantially evenly across a front surface of the spectrometer configured to receive the light, such as across a lateral dimension of a filter array. The substantially even spatial distribution of light can be uniform across the front surface of the spectrometer to within about 25%, or to within about 10%. For example, light can be distributed substantially even across a lateral dimension of the filter array such that the light transmitted to each filter of the filter array can be substantially homogenous with respect to the spatial distribution profile. These methods and devices may be incorporated with any embodiment of a compact spectrometer as described herein.
Output light 205b from the second diffuser can have an intensity distribution that varies across the width or the area of the diffuser. For example, output light exiting the second diffuser at locations relatively farther from the location 2720 on which the incident light 200 impinges on the first diffuser can have a relatively lower intensity compared to output light exiting the diffuser at locations relatively closer to the location 2720. To reduce this spatial variation in the intensity of output light, the separation distance 2717 between the two diffusers can be increased. The spectrometer can be configured with two or more diffusers that are separated by a distance 2717 that is greater than or substantially similar to a width of the desired light output area. For example, the two diffusers can be separated by a distance that is approximately half of the output lateral dimension of the filter array (e.g., half of the width of filter matrix 170 shown in
The spectrometer can be configured with more than two cosine diffusers, such as three or more diffusers, arranged sequentially along the optical path of the light from the sample.
Alternatively or in addition to the cosine diffusers as shown in
The diffusivity of a lateral diffuser and hence the extent of lateral distribution of input light exiting the lateral diffuser may be controlled by varying one or more of the refractive index of the scattering structures, refractive index of the support material, the size of the scattering structures, the number or density per unit volume of the scattering structures, and the overall thickness of the diffuser. The thickness of the lateral diffuser and the size and density of the plurality of scattering structures may be arranged such that a majority of light exiting the lateral diffuser is scattered by at least two light scattering structures. One or more properties of the lateral diffuser can be controlled to configure the diffuser such that for input light having any full-width half maximum (FWHM) value, the FWHM of the output light is in a range which is relatively large compared to the size of each optical channel or each filter of the filter array. For example, in a lateral diffuser having a thickness of about 100 um, comprising scattering particles having a diameter of about 10 um at a particle concentration of about 2.5%, assuming ideal scatter wherein the light is very efficiently scattered in substantially all directions, input light of any spot size may result in output light having a FWHM of at least about 0.3 mm.
In operation, the input light 200 incident on the input surface 2765 of the lateral diffuser hits one or more of the plurality of scattering structures as the light is transmitted through the diffuser. The scattering structures can scatter the incident light in a plurality of directions, as shown in
For example, the input light can hit a first scattering structure 2760a, scattering the light in a first direction 201a and in a second direction 201b. The light scattered in the first direction 201a can subsequently hit a second scattering structure 2760b, and light scattered in the second direction 201b can subsequently hit a third scattering structure 2760c. Light impinging on the second scattering structure 2760b can scatter in a plurality of directions and exit the diffuser from the output surface 2770 at the second location 2782 and third location 2784 along the width of the lateral diffuser. Light impinging on the third scattering structure 2760c can be further scattered in a first direction 202a and a second direction 202b. The light scattered in the first direction 202a can hit a fourth scattering structure 2760d, subsequently scatter in another direction to hit a fifth scattering structure 2760e, then exit the diffuser from the output surface 2770 at the fourth location 2786. The light scattered in the second direction 202b can hit a sixth scattering structure 2760f, and subsequently scatter in another direction to exit the diffuser from the output surface at a fifth location 2788.
Examples of commercially available lateral diffusers and additional details regarding the principle of operation of a lateral diffuser as herein described may be found on the Internet, for example, at http://www.entire.com.tw/english/product1.htm (Entire Technology Co. LTD diffuser plate) and http://www.chimeicorp.com/en-usiproducts/electronic-materials/optical-grade-diffliser-plate/ (CHIMEI optical grade diffuser plate).
Optionally, a lateral diffuser may also be a cosine diffuser, configured to angularly distribute light according to a cosine function. In such a case, the same diffuser can both angularly and spatially distribute input light, such that the profile of transmitted diffuse light is substantially uniform both along a spatial or lateral dimension, as well as in the angular dimension.
Referring again to
One exemplary configuration of the first cosine diffuser 2700a and second cosine diffuser 2700b in an optical stack is shown in
Stray Light Reduction
Diffuse light transmitted through the diffuser can enter the optical stack at many angles. Light that enters the optical stack at large angles with respect to the normal to the plane of the optical stack may be reflected from one or more channel side walls defining the channels of the support array, and reach the image sensor at unintended angles such that the light may be difficult to resolve spectrally. Alternatively or additionally, light entering the optical stack at large angles may pass from one channel to an adjacent channel, causing mixing of light between different optical channels and consequently ambiguity in the spectral resolution of the input light. Arrow 2850 illustrates stray light caused by the reflection of light from the channel side walls 2829 of the support array. Arrow 2852 illustrates stray light caused by the passing of light between adjacent channels.
The spectrometer can be configured in one or more of many ways to reduce or eliminate the amount of stray light that reaches the image sensor. For example, the aperture array may comprise a first aperture array layer and a second aperture array layer configured to limit the angles of light that can pass through the aperture array; the filter array may comprise an opaque material disposed between adjacent filters; the channel side walls of the support array may comprise micro features configured to redirect or absorb light having large angles; the support array may comprise channel bottom walls having a central openings therethrough; the optical stack may comprise angle limiting layers configured to limit the angles of light that enter the optical stack, such as a micro-louver film or a prism film. Each of these elements or features may be incorporated into a spectrometer as described herein alone or in combination with one or more other elements or features, to achieve the desired reduction of stray light as well as improved light transmission efficiency.
Filter Array with Opaque Material, Aperture Array Comprising Two Aperture Array Layers
The opaque material 2914 can comprise any material configured to prevent cross-talk of light between adjacent filters of the filter array, such as an opaque glue or coating configured to substantially absorb light that impinges upon the material. Arrow 2952 shows light entering the optical stack at a large angle of incidence, such that the light, if uninterrupted, would cross between two or more adjacent filters while traveling through the filter array. In the configuration of
The first and second aperture array layers can be arranged to block light entering the optical stack at an angle of incidence outside a predetermined range that is deemed acceptable for the normal operation of the spectrometer. Arrows 2950a and 2950b show light entering the optical stack at the maximum angle of incidence 2954 allowed to pass through the aperture array 2915. As illustrated in
wherein α is the maximum angle of incidence 2954 of light allowed to pass through the aperture array, L is the first diameter 2963 of the first aperture, S is the second diameter 2973 of the second aperture, and D is the effective separation distance between the first and second aperture array layers, or the free-space separation distance 2919 divided by the refractive index of the medium. Thus, one or more of the first diameter, the second diameter, and the separation distance may be adjusted to achieve a predetermined, desired value of the maximum angle of incidence 2954. For example, to achieve a maximum allowed angle of incidence of 40°, the first plurality of apertures can be configured to have a first diameter of about 1 mm, the second plurality of apertures can be configured to have a second diameter of about 0.68 mm, and the first and second aperture array layers can be disposed at a separation distance of about 1 mm. In many cases, the predetermined range for the angles of incidence of input light allowed to pass through the aperture array can be from about −40° to about 40° with respect to the normal to the plane of the optical stack. Depending on the specific configuration of the optical stack, the predetermined range can be increased to a wider range (e.g., from about −50° to about 50°), or decreased to narrower range (e.g., from about −30° to about 30°).
Support Array Channel Side Walls Comprising Micro Features
The side walls of the plurality of channels may be configured to provide substantially specular reflection of light from the side walls, for example by providing polished side walls. Alternatively or in combination, side walls of the plurality of channels may be configured to provide substantially diffusive reflection of light from the side walls, such that the reflected light may be scattered to many directions.
Support Array Channels Comprising Bottom Wall with Central Opening
In the configurations shown in
The performance characteristics of the channel comprising the bottom wall can depend on the ratio between the cross-sectional area of the channel and the area of the central opening. Large ratios, corresponding to relatively larger areas of the bottom wall that can block light traveling towards the bottom end of the channel, can allow a smaller range of angles of light to pass through the channel. In exemplary configurations, the ratio between the cross-sectional area of the channel and the area of the central opening can be in a range from about 1.1 to about 1.5, in a range from about 1.2 to about 1.4, or about 1.3. In one exemplary configuration, a channel may have an internal diameter of about 576 um, and a center opening with a diameter of about 500 um, corresponding to a ratio of about 1.33 between the cross-section area of the channel and the area of the central opening. In some configurations, the cross-sectional area of the channel may be increased by reducing the thickness of the channel side walls.
Angle Limiting Layer
Alternatively to or in combination with one or more of the configurations discussed in reference to
The maximum angle of incidence of light allowed to pass through the micro-louver film may be calculated using the following equation:
wherein α is the maximum angle of incidence of light allowed to pass, D is the distance between adjacent light blocking sections, and T is the effective thickness of the micro-louver film, or the free-space thickness divided by the index of refraction of the film. Thus, the maximum allowed angle of incidence may be controlled by adjusting one or more of the thickness of the micro-louver film and the distance between adjacent light blocking sections. For example, to achieve a maximum allowed angle of incidence of 40°, assuming the light transmissive sections of the micro-louver film have an average index of refraction of about 1.3, the micro-louver film can be arranged to have a thickness of about 500 um, and a distance between adjacent light blocking sections of about 322 um. In many cases, the predetermined range for the angles of incidence of input light allowed to pass through the micro-louver film can be from about −40° to about 40° with respect to the normal to the plane of the optical stack. Depending on the specific configuration of the optical stack, the predetermined range can be increased to a wider range (e.g., from about −50° to about 50°), or decreased to narrower range (e.g., from about −30° to about 30°). An example of a commercially available micro-louver film suitable for incorporation with a spectrometer as described herein may be found on the Internet, for example, at http://multimedia.3m.com/mws/media/793096O/3mtm-privacy-filter-alcf-p-abr0-film-data-sheet.pdf?fn=ALCF-P_ABR0_Control_Film_DS.pdf (3M Advanced Light Control Film).
To control the maximum angle of incidence of light allowed to pass through the prism film, one or more of the thickness of the film, the angle between adjacent microstructures, and the pitch of each microstructure may be adjusted. For example, for a maximum angle of incidence of about 35° with respect to the normal to the plane of the prism film, the prism film may be configured to have a thickness of about 62 um, an angle of about 90° between adjacent microstructures, and a pitch of about 24 um for each microstructure. To achieve better uniformity, the pitch of each microstructure may be minimized. An example of a commercially available prism suitable for incorporation with a spectrometer as described herein may be found on the Internet, for example, at http://multimedia.3 m.com/mws/media/157408O/vikuiti-tm-t-bef.pdf?fn=T-BEF.pdf (3M Vikuiti™ Thin Brightness Enhancement Film).
Control of Input Light Entering Spectrometer Module
In embodiments of the spectrometer comprising an integrated illumination module, light generated by the illumination module and directed towards the sample is generally reflected back from the sample towards the spectrometer in a known, limited range of angles of reflection. Accordingly, light that reaches the spectrometer module or optical stack of the spectrometer at angles that are outside the known range of angles of reflection for the illumination light may be assumed to have originated from sources other than the illumination module (e.g., ambient light, stray light), and may be prevented from entering the optical stack in order to improve the spectral resolution of sample light by the spectrometer. For example, an optical shading configured to block the undesired angles of light may be incorporated into the spectrometer. Alternatively or additionally, a micro-louver film or a prism film as described herein may be incorporated into the spectrometer. For example, referring again to the spectrometer module 160 shown in
The methods and apparatus disclosed herein can be incorporated with components from spectrometers known in the art, such as spectrometers described in U.S. Pat. No. 8,284,401, U.S. Pat. No. 7,236,243, U.S. Publication No. 2015/0036138, U.S. Pat. No. 9,060,113, and U.S. Publication No. 2014/0061486, the entire disclosures of which are incorporated herein by reference.
Although the detailed description contains many specifics, these should not be construed as limiting the scope of the disclosure but merely as illustrating different examples and aspects of the present disclosure. It should be appreciated that the scope of the disclosure includes other embodiments not discussed in detail above. Various other modifications, changes and variations which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the method and apparatus of the present disclosure provided herein without departing from the spirit and scope of the invention as described herein.
While preferred embodiments of the present disclosure have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will be apparent to those skilled in the art without departing from the scope of the present disclosure. It should be understood that various alternatives to the embodiments of the present disclosure described herein may be employed without departing from the scope of the present invention. Therefore, the scope of the present invention shall be defined solely by the scope of the appended claims and the equivalents thereof.
Claims
1. An apparatus to measure spectra of a sample, comprising:
- a detector having a field of view to measure the spectra of the sample within the field of view;
- a light source to direct an optical beam to the sample within the field of view, wherein a portion of the optical beam reflected from the sample is visible to a user.
2. An apparatus as in claim 1, wherein the portion of the optical beam reflected from the sample visible to the user defines a measurement area of the sample.
3. An apparatus as in claim 1, further comprising a casing supported with the detector and the light source, the detector and the light source arranged to fit within the casing, the casing sized to fit within a hand of the user to allow the user to aim the spectrometer at the sample and measure the sample.
4. An apparatus as in claim 3, further comprising a user input supported with the casing and arranged for the user to aim the spectrometer and measure the sample with the user input manipulated with the hand holding the spectrometer.
5. An apparatus as in claim 4, further comprising circuitry coupled to the detector and the light source, the circuitry configured to transmit the optical beam in response to the user input with the hand holding the hand held spectrometer.
6. An apparatus as in claim 1, wherein the light source is configured in order to provide the optical beam incident on the sample with an illuminance (Ev) within a range from about 20 lux (lm/m2) to about 100,000 lux (lm/m2).
7. An apparatus as in claim 1, wherein the light source is configured to provide the optical beam incident on the sample with an irradiance within a range from about 0.1 mW/cm2 to about 100 mW/cm2.
8. An apparatus as in claim 1, the portion of the optical beam visible to the user comprises a portion of a measurement beam to measure the spectra of the sample.
9. An apparatus as in claim 1, the portion of the optical beam visible to the user comprises an aiming beam comprising one or more wavelengths corresponding to one or more colors visible to the user.
10. An apparatus as in claim 9, wherein the one or more colors visible to the user comprises one or more of red, orange, yellow, blue, green, indigo or violet.
11. An apparatus as in claim 1, wherein the portion of the beam visible to the user comprises a combination of visible wavelengths of light.
12. An apparatus as in claim 1, wherein the optical beam comprises an aiming beam and a measurement beam arranged to illuminate the sample within the field of view of the detector.
13. An apparatus as in claim 12, wherein the detector comprises one or more filters to inhibit transmission of the aiming beam and to transmit the measurement beam.
14. An apparatus as in claim 13, wherein the one or more filters comprises a plurality of optical filters to inhibit transmission of a portion of the aiming beam reflected from the sample and to transmit a portion of the measurement beam reflected from the sample.
15. An apparatus as in claim 14, wherein the detector comprises a plurality of optical channels, each of the plurality of optical filters corresponding to an optical channel, each optical channel comprising a field of view
16. An apparatus as in claim 1, wherein the field of view comprises a plurality of overlapping fields of view of a plurality of optical channels and wherein the aiming beam and the measurement beam are arranged to overlap with the plurality of overlapping fields of view on the object.
17. An apparatus as in claim 1, further comprising a second light source to direct a measurement beam toward the sample, the first light source comprising an aiming beam.
18. An apparatus as in claim 17, wherein the measurement beam comprises an infrared beam and the aiming beam comprises a visible light beam.
19. An apparatus as in claim 1, further comprising:
- one or more optics coupled to the light source to direct the optical beam toward the sample.
20. An apparatus as in claim 19, wherein the one or more optics comprises one or more of a mirror, a beam splitter, a lens, a curved reflector, or a parabolic reflector to direct the optical beam toward the sample.
21.-130. (canceled)
Type: Application
Filed: Aug 2, 2017
Publication Date: May 17, 2018
Inventors: Damian Goldring (Tel Aviv), Dror Sharon (Benei Atarot), Sagee Rosen (Netzer Sireni), Ittai Nir (Tel Aviv), Uri Kinrot (Hod HaSharon), Omer Keilaf (Kfar Saba), Guy Brodetzki (Rehovot), Amir Levy (Tel Aviv), Elad Heiman (Tel Aviv), Idan Bakish (Petah-Tikva)
Application Number: 15/667,360
