Abstract: A purpose of the present invention is to provide an optical measurement system or the like suitable for optical measurement of nucleic acids, proteins, etc. In a first aspect of the present invention, an optical measurement system that provides optical sample measurement comprises: an optical cell having a sample-holding hollow portion; and a light source unit that emits broadband light containing first and second light to the optical cell. The optical cell includes: a first light guide where light passes through a first transparent portion that transmits the first light more readily than the second light and the hollow portion without passing through a second transparent portion that transmits the second light more readily than the first light; and a second light guide that differs from the first light guide, in which light passes through the second transparent portion and the hollow portion without passing through the first transparent portion.

Abstract: An apparatus includes an image system for obtaining a digital image of a test strip and a processing system to identify the colors of the test strip, compare the colors to a standard and identify the likelihood that the test strip falls with the standard.

Abstract: Some aspects of the present disclosure relate to a system having a substrate device, a substrate support surface, and a substrate handler that positions the substrate device on the substrate support surface. The substrate device and the substrate support surface may have counterpart coarse position units and fine position units. The system may measure coarse positional offsets between the first and second coarse position units, re-position the substrate device on the substrate support surface based on the coarse positional offsets, and subsequently measure fine positional offsets between the first and second fine position units. In some implementations, the substrate device is integrally coupled to the substrate handler via a wireless communication link in order to communicate position information as feedback for further placement.

Abstract: The present disclosure provides an optical device for selecting specific matter, such as plant matter. The device comprises a light source for emitting light having at least (3) wavelengths and for generating a combined beam of light having the at least 3 wavelengths. The device further comprises an optical element for directing a plurality of light beams towards matter including the specific matter. The optical element has first surface portions through which in use the plurality of component light beams are directed to the matter including the specific matter. Each component light beam is directed through a respective first surface portion that has an optical property that is selected so that light intensity differences between the component light beams are reduced.

Abstract: Portable spectrophotometer and method for characterizing solar collector tubes for simultaneously and on-field characterizing reflection and transmission coefficients. This device includes all the components needed to take this measurement, such as a module that takes the measurement of the reflection coefficient (R) of the inner tube (1?), a module that takes the measurement of transmission coefficient (T) of the outer tube (1?), an electronic data acquisition and processing system (12), an external computer (13) for controlling the device and sending the measured data (17) and a communication system (15) between device and the computer (13).

Abstract: This invention provides a novel methods and devices for measurement of particle concentration or changes in particle concentration over a wide linear range. The invention comprises one or more radiation sources and one or more detectors contained in a housing which is interfaced to a medium containing particulate matter. The one or more radiation sources are directed into the medium, scattered or transmitted by the particulate matter, and then some portion of the radiation is detected by the one or more detectors. Methods for confining the measurement to a specific volume within the medium are described. Algorithms are provided for combining the signals generated by multiple source-detector pairs in a manner that results in a wide linear range of response to changes in particle concentration. In one embodiment the sensor provides non-invasive measurements of biomass in a bioreactor. In another embodiment an immersible probe design is described, which may be suited for one-time use.

Abstract: The optical assemblies disclosed herein advantageously utilize a beamsplitting apparatus in association with (i) the illumination path or (ii) the collection path of a color measurement instrument. Thus, the beamsplitting apparatus may be configured to spectrally divide one or more initial beams of light to emit a plurality of resultant beams of light, wherein the optical assembly is configured to illuminate a target using at least a first and second of the plurality of resultant beams. Alternatively, the beamsplitting apparatus may be configured to spectrally divide light received from a target to emit a plurality of resultant beams of light, wherein the optical assembly is configured to detect at least a first and second of the plurality of resultant beams of light. Advantageously, each of the first and second resultant beams is a product of a distinct set of one or more spectral constraints exacted by the beamsplitting apparatus.

Abstract: A color measuring device includes a lighting arrangement for a measurement field of a measurement object to be measured, a pick-up arrangement for detecting the measurement light reflected back from the measurement field and for converting it into corresponding electric signals, an electronic circuit for controlling operation of the color measuring device and for processing and evaluating the electric signals, and a display for displaying measurement results. The lighting arrangement has a lamp ring with three identical lamp groups for illuminating the measurement field from a predefined range of angles of incidence. The pick-up arrangement has a digital camera which creates an image of the measured measurement field. The electronic circuit is designed to switch the light sources of the lamp groups on sequentially, and the camera creates a separate image of the measurement field for every switched-on light source.

Abstract: A semiconductor wafer may include a dummy field configured to enable overlay measurements. The enhanced dummy field may include a plurality of encoding blocs that enable OVL measurements to be made throughout the enhanced dummy field.

Abstract: In various embodiments of the invention, a unique construction for Light Emitting Diodes (LEDs) with at least one luminescent rod and extracting optical elements is used to generate a variety of high brightness light sources with different emission spectra. In an embodiment of the invention, forced air cooling is used to cool the luminescent rod. In an embodiment of the invention, totally internal reflected light can be redirected outward and refocused. In another embodiment of the invention, light emitted by the luminescent rod is out-coupled for use in a variety of applications. In various embodiments of the invention, a plurality of independent narrow band colors can be coaxially combined.

Abstract: A semiconductor wafer may include a dummy field configured to enable overlay measurements. The enhanced dummy field may include a plurality of encoding blocs that enable OVL measurements to be made throughout the enhanced dummy field.

Abstract: The optical assemblies disclosed herein advantageously utilize a beamsplitting apparatus in association with either (i) the illumination path or (ii) the collection path of a color measurement instrument. For implementations involving the illumination path, the beamsplitting apparatus may be configured to spectrally divide one or more initial beams of light so as to emit a plurality of resultant beams of light, wherein the optical assembly is configured to illuminate a target using at least a first and a second of the plurality of resultant beams of light. Similarly, for implementations involving the collection path, the beamsplitting apparatus may be configured to spectrally divide light received from a target so as to emit a plurality of resultant beams of light, wherein the optical assembly is configured to detect at least a first and a second of the plurality of resultant beams of light.

Abstract: A light emitting diode (LED) based detection system is employed for spectroscopy based applications. LEDs are used as monochromatic light sources for applications at specific and pre-defined wavelengths. Spectrographic information is generated using LEDs of different wavelengths ranging from 260 nm to 1400 nm. Multiple wavelength information is generated by coupling light from each LED into an intensity and mode mixing fiber bundle. A dual beam approach of using a reference and a sample photodiode ensures automatic drift correction. Interference filters at the LED input fiber reduce the spectral bandwidth of the monochromatic light emission to a useful 10 nm bandwidth by cutting off the LEDs trailing emission distribution allowing for absorbance measurements similar to typical spectrometers.

Abstract: A light emitting diode (LED) based detection system is employed for spectroscopy based applications. LEDs are used as monochromatic light sources for applications at specific and pre-defined wavelengths. Spectrographic information is generated using LEDs of different wavelengths ranging from 260 nm to 1400 nm. Multiple wavelength information is generated by coupling light from each LED into an intensity and mode mixing fiber bundle. A dual beam approach of using a reference and a sample photodiode ensures automatic drift correction. Interference filters at the LED input fiber reduce the spectral bandwidth of the monochromatic light emission to a useful 10 nm bandwidth by cutting off the LEDs trailing emission distribution allowing for absorbance measurements similar to typical spectrometers.

Abstract: The invention discloses a system for optical spectroscopy comprising a multi-wavelength semiconductor light source comprising a plurality of semiconductor light sources disposed on a silicon sub-carrier and emitting a plurality of radiation components spanning a wavelength range. The radiation components are coupled to a waveguide array disposed on the same silicon subcarrier. Output from the waveguide array provides a compact multi-wavelength laser source with wide tuning range via a plurality of laser sources. The system further comprises means for directing radiation components to a sample, and an optical detector configured to detect one of a radiation reflected from and transmitted through said sample. The system can be used in a variety of applications including the analysis of in-vivo human tissue, agricultural samples, and pharmaceutical samples. Typical wavelength ranges are 650-1000 nm, 700-1700 nm, and 1100-2500 nm.

Abstract: A peripheral interface device for determining the color of a surface, where the surface color may then be used to determine device position and identify objects. Embodiments provide a device capable of directing different colors of light (e.g., red, green and blue) onto a surface and measuring relative intensities of the reflected colors to determine the color of the surface. The reflection and measurement of each color may be performed separately. Alternatively, composite-colored light may be directed at the surface, which may then be filtered to extract the different colors and enable measurement of their relative intensities. As such, the device can detect regions of a given color and regions of different shades of the same color, which may then be used to determine the position of the device and/or identify an object.

Abstract: A color measurement instrument and color measurement method for measuring a color of a surface are provided. The instrument includes a plurality of independently switchable light sources characterized by differing spectral ranges, and a plurality of light guides configured to receive light from the light sources and to direct the received light to a light emitting portion of the instrument for illuminating the surface. The instrument further includes a first light detector configured to receive a portion of the light reflected from the surface. The first light detector is a wideband light detector.

Abstract: A system and method for full width scanning color analysis of a printed media sheet are disclosed. The full width array spectrophotometer system includes one or more substantially linear elongated illumination arrays of closely spaced multiple illumination sources. The sources include sets of illumination sources, including a first set of different color illumination sources and a second set including one or more UV-emitting illumination sources. The sets are arranged to span a printer paper path or other object path to illuminate a band extending transversely across a printed print media sheet or other object moving in the path. A full width array light imaging sensor includes an elongated array of multiple closely spaced photodetectors for detecting plural colors and is positioned adjacent to and extending substantially parallel to the linear array(s) to receive radiation reflected from the transverse illuminated band.

Abstract: Methods for determining chlorophyll content comprise providing a sample, subjecting the sample to light at a first wavelength and detecting a first wavelength response, subjecting the sample to light at a second wavelength and detecting a second wavelength response, and calculating a chlorophyll content of the sample based on at least the first wavelength response and the second wavelength response. Optional approaches include detecting the nitrogen content and/or water content of the sample. Associated apparatus for determining chlorophyll content, which may comprise a handheld device, is also disclosed.

Abstract: An optical reader having an array of differing-color light sources and a controller for controlling the light sources and acquisition of optical data. The light sources are arranged, and the controller is configured, to allow rapid acquisition of optical data regarding individual sample wells of a cluster of such wells. In some embodiments, multiple ones of the differing-color light sources are illuminated simultaneously for acquiring optical data on a corresponding number of sample wells. Depending on the configuration of the array and number of differing-color light sources illuminated simultaneously, the optical reader can acquire optical data for several wavelengths in a fraction of the time of conventional optical readers. Other embodiments include one or more non-contact temperature sensors for acquiring temperature data substantially simultaneously with the optical data.

Abstract: A color density measuring device (10) for determining the color density of an ink layer applied to a printing material (22), having a light source (24) for illuminating the printing material (22) and a sensor for receiving the light remitted from the printing material (22), is characterized according to the invention in that the sensor is fashioned as a multicolor image sensor (12), and a device (14, 24, 26; 30) is provided with the aid of which the light incident at the multicolor image sensor (12) is restricted to at least one predetermined wavelength band.

Abstract: A hand-held colorimetric device (101) suitable for use by blind or color-blind individuals to determine the color of a surface-under-test (SUT), for example of a fabric, has an aperture (110) which, in use, is covered by the SUT (113) whose color is to be determined. Six LEDs (115A, 115B, 116B, 117A and 117B) arranged in pairs (115A/115B, 116A/116 B, 117a/117B) emitting red/orange, green, and blue light illuminate the SUT and diffuse reflections therefrom containing red/orange, green, and blue spectrum sample values are used to determine the luminous reflectivity and chromaticity values for the color of the SUT. The measured values are compared with colorimetric values of reference surfaces to determine the color of the SUT. The colorimetric device may output the name of the color aurally.

Abstract: A system of measuring light transmission and/or reflection has a light transmitter(s) and at least one light sensor which are used to generate a defined light environment over a specified light frequency range.

Abstract: A multi-spectrum image capturing device includes a multi-spectrum illuminating device comprising LED's for emitting lights of different wavelengths from one another, a plurality of optical rods for relaying the lights emitted from the LED's, an optical diffusion element for diffusively reflecting the lights from the optical rods by a white diffusion surface and an aluminum-coated reflecting surface to be irradiated at an angle of about 60° with respect to an image-capturing optical axis, and an optical sheet for further diffusing the lights from the optical diffusion element, and also includes an image-capturing optical system and a CCD for forming an image based on lights reflected from an irradiated surface under illumination by the multi-spectrum illuminating device to capture the formed image. An image output captured by the CCD is analyzed to measure color components of the irradiated surface.

Abstract: Systems and methods for providing spectral measurements are described. In one embodiment, a spectral measuring device comprises at least one radiation source configured to provide N (N?2) linearly independent illuxninant sources characterized by M (M?N) wavelength channels in a predetermined wavelength range; a sensor unit including at least one sensor, configured to be in optical communication with the radiation sources and an object; a memory storing an illuminant characterization matrix including spectral characteristics of the N illuminant sources in the M wavelength channels; and a processor configured to provide spectral responses of the object in the M wavelength channels, based at least in part on the illuminant characterization matrix. The embodiments of the invention can be used to construct a new class of compact spectral measuring devices, such as handheld color measuring devices.

Abstract: A multi-spectrum image capturing device includes a multi-spectrum illuminating device comprising LED's for emitting lights of different wavelengths from one another, a plurality of optical rods for relaying the lights emitted from the LED's, an optical diffusion element for diffusively reflecting the lights from the optical rods by a white diffusion surface and an aluminum-coated reflecting surface to be irradiated at an angle of about 60° with respect to an image-capturing optical axis, and an optical sheet for further diffusing the lights from the optical diffusion element, and also includes an image-capturing optical system and a CCD for forming an image based on lights reflected from an irradiated surface under illumination by the multi-spectrum illuminating device to capture the formed image. An image output captured by the CCD is analyzed to measure color components of the irradiated surface.

Abstract: The present invention provides an optical sensor having one or more filter-photodetector pairs and feedback to monitor the intensity and chromaticity of the white light generated by an illumination system. According to the present invention, filter-photodetectors are configured into pairs thereof, wherein a first filter-photodetector of a pair is configured and arranged so as to be sensitive to a predetermined region of the electromagnetic spectrum, while a second filter-photodetector of the pair is configured and arranged to be sensitive to a substantially complementary region of the electromagnetic spectrum. The spectral responsivity of the first filter-photodetector and the second filter-photodetector overlap in a predetermined region of the electromagnetic spectrum.

Abstract: A two-dimensional spectroradiometer has an optical system such as an objective optical system 2 and a relay lens 6 for receiving light rays La from a two-dimensional light source L to form an optical image i.e. a first image 2a and a second image 6a, a WBPF 12 as a transmittance wavelength variable filter having a spectral transmittance characteristic that transmittance wavelengths of the light rays La differ from each other depending on transmittance sites of the filter where the respective light rays La pass, a scanning WBPF 10 which scannably holds the WBPF 12 on an optical path forming the optical image, and an image sensor 7 for capturing the second image 6a composed of the light rays La passing through the WBPF 12 at a position corresponding to each of scanning steps of the WBPF 12 to acquire a plurality of images each having a different spectral sensitivity among pixels of the image at the position corresponding to the each of the scanning steps.

Abstract: The Apparatus for determining the color stimulus specification of a translucent object, for example of a tooth, comprises an illumination device as well as an image capture device. For illuminating the object under test with light in different wave length portions, the illumination device comprises an LED array with a plurality of sequentially energizable light emitting diodes. Several different types of light emitting diodes are provided, each emitting light in a different wave length portion.

Abstract: Described is a dark-field imaging device for the spatially resolved dark-field imaging of a sample (60), especially a fluorescent sample, comprising, for the illumination of the sample with excitation light, an illumination assembly (20) comprising a grid (22) of individually addressable light sources (24), wherein the lines connecting the light sources and the sample define a region (64) with the optical path of the direct excitation light and a region (66) with the optical path of the specular reflected excitation light, and a detection assembly (30) for the detection, with radiation-receiving elements (34), of the radiation emitted by the sample (60) as an optical response to the illumination, wherein the radiation-receiving elements (34) of the detection assembly (30) are disposed outside the region (64) with the optical path of the direct excitation light and the region (66) with the optical path of the specular reflected excitation light.

Abstract: Tone reproduction curves for calibrating a marking system are obtained using a test pattern with a plurality of patches, preferably a plurality of first test patches extending in a first direction and at least one second test patch extending in a second direction crossing the first direction. Reflectance values are obtained from the first and second test patches. A set of gray balanced tone reproduction curves are obtained based on the reflectance values of the first test patches, and a set of spatial gray balanced tone reproduction curves are obtained based on the reflectance values of the second test patches.

Abstract: A system for sensing an absolute position in two dimensions includes a target having a two-dimensional target pattern. A sensor captures an image of a first subset of the target pattern. A controller generates a first image vector representing summations of rows of pixel values from the image, and a second image vector representing summations of columns of pixel values from the image. The controller is configured to determine an absolute two-dimensional position of the first subset with respect to an origin of the target pattern based on the first and the second image vectors and a plurality of target vectors that represent the target pattern.

Abstract: A method and apparatus for color measurement using a physically distributed multiplicity of sensors. Broad band illumination is provided to irradiate a test pattern. The sensors are used to measure color characteristics of discrete areas of a region of the pattern that has an intended single color by providing the pattern and sensors arrayed in a substantially matching geometric configuration.

Abstract: The illustrative embodiment of the present invention is a system and a method for the detection and identification of biological agents. The system incorporates elements that enable it to obtain an air sample, extract particulates from the air sample onto a stationary-phase collection media, expose the particulates to electromagnetic radiation, and monitor for fluorescent emissions. In some embodiments, particulates are exposed to electromagnetic radiation using a plurality of LEDs, wherein some of the LEDs emit electromagnetic radiation at relatively shorter wavelengths and some other of the LEDs emit electromagnetic radiation at relatively longer wavelengths.

Abstract: A spectrum measuring apparatus that includes an extinction member for decreasing a light intensity from an EUV light source, a spectrum member for extracting light with a desired wavelength band from the decreased intensity light and a detector for detecting a light intensity of the light with a desired wavelength band is disclosed. Then, a spectrum intensity distribution (spectrum) is obtained by (a) a plural opening is located in the extinction member, and the light from the EUV light source passes through the plural opening at the same time, or (b) the detector detects the light volume of the light with a desired wavelength band as thermal energy.

Abstract: A double path microdrop optical biometric system comprises a micro container, a corner cube array, a collimator, a beam splitting device, a light source selector, a detector and a signal comparator unit. It utilizes the beam to penetrate a specimen with specific coloring agent twice. Then, the shade of the beam can be detected so that a signal comparator unit can calculate the absorptance. The required volume of the specimen used in the system is small. The precision will be doubled by the double path design. Its entire optic-electronic system is simple and at low cost. By using the LEDs, it can avoid the use of filter and solve the over-heating problem. Plus, it can execute many bio-chemical tests.

Abstract: A method, includes illuminating a first portion of a colored region with first light from a gas discharge tube and generating a first output using a diffuse reflection of the first light from the first portion. The method further includes illuminating a second portion of the colored region with second light from a first solid state lamp and generating a second output using a diffuse reflection of the second light from the second portion. Additionally, the method includes illuminating a third portion of the colored region with third light from a second solid state lamp and generating a third output using a diffuse reflection of the third light from the third portion.

Abstract: A scanning analyzer unit comprises a scanner device, a signal amplifier, an analog/digital converter, a driver device, a controller device, a computing unit, and a RS-232 interface. After chemical, biological, or chemi-enzymatic reaction, a resulting color change of a testing support through reacted multi-chromogens therein is quantified by means of the scanning analyzer unit. Via the sensitivity differences of the multi-chromogens at a fixed wavelength of the scan, multi-analyte concentrations of wide range variations in one sample can be simultaneously assayed.

Abstract: The relative position of two members is determined based upon a detected relative intensities of first and second colors of light. The intensity balance associated with relative occlusion of first and second color filter portions on one member by a mask on the other member. An exemplary use is in rotational position sensing within a limited rotation range. With a given compliance between the two members, the position sensing can be used as a proxy for torque sensing.

Abstract: A color-simulating apparatus is provided, which can be applied to change the color of an article to various colors. The color-simulating device first analyzes a color to be simulated and then produces a light having the color according to the analysis result. Lastly, the color light is used to provide the color of an article.

Abstract: An absolute 2D position-sensing device is usable to measure the relative position of two elements. A 2D absolute scale includes an integrated 2D absolute scale pattern extending over the 2D scale area along each measuring axis of the scale. The integrated 2D absolute scale pattern includes a plurality of periodic portions interleaved with a plurality of non-periodic portions along each axis. Each periodic portion includes a plurality of periodically-placed scale elements. Each non-periodic portion includes a plurality of code elements indicative of an absolute measurement value. The code elements may have a length that is narrower along each measuring axis is than the length of the periodic scale elements along each measuring axis. The offset of the periodically-placed elements relative to a readhead of the device is combined with the absolute measurement value to determine an absolute position.

Abstract: An improved and lower cost color spectrophotometer, especially suitable for on-line color printer color control systems, incorporating a low cost commercial imaging chip, which normally only forms part of a three row, three color, document imaging bar used for imaging documents in scanners, digital copiers, or multifunction products, having multiple photo-sites with at least three different color filters in three rows. This multiple photo-sites chip may be modified to also provide unfiltered photo-sites. This spectrophotometer may have a substantially reduced number of different LED or other spectral illumination sources, one of which may be for white light, yet provide multiple spectral data outputs from the differently filtered photo-sites being simultaneous illuminated by the light reflected from a color test target area which is being sequentially illuminated by the respective limited number of LEDs, enabling broad spectrum information and color control.

Abstract: A color spectrophotometer incorporating a low cost commercial imaging chip, which normally forms part of a document imaging bar used for imaging documents in scanners, etc., having multiple photo-sites with three different rows of color filters. Each chip is mounted on the optical axis of an imaging lens system, in the image plane of that lens system, to image the reflected illumination from an illuminated color test target area on the chip. The optical axis of the imaging lens system is oriented at 45° to the illuminated color test patches, and the photodetector chip is physically mounted perpendicular to the plane of the illuminated color test patches. Respective photo-sensor chips and associated 1:1 optics may be mounted on opposing sides of the spectrophotometer physically oriented at 90° to the test target area plane receiving the reflected light from the test target optically oriented at 45° to the illuminated test target.

Abstract: A color spectrophotometer incorporating a low cost commercial imaging chip, which normally forms part of a document imaging bar used for imaging documents in scanners, etc., having multiple photo-sites with three different rows of color filters. Each chip is mounted on the optical axis of an imaging lens system, in the image plane of that lens system, to image the reflected illumination from an illuminated color test target area on the chip. The optical axis of the imaging lens system is oriented at 45° to the illuminated color test patches, and the photodetector chip is physically mounted perpendicular to the plane of the illuminated color test patches. Respective photo-sensor chips and associated 1:1 optics may be mounted on opposing sides of the spectrophotometer physically oriented at 90° to the test target area plane receiving the reflected light from the test target optically oriented at 45° to the illuminated test target.

Abstract: A limited number of voltage measurements are received from a multiple illuminant color sensor at the direction of a color sensor controller. The received sensor voltages are normalized in accordance with a calibration look-up table. Next, the normalized sensor voltages are converted to reflectance values based on a correction look-up table. Then, a reconstruction look-up table is used to convert the reflectance values at a predetermined wavelength to reflectance values with a predetermined wavelength separation.

Abstract: A color analyzer is capable of determining the color property of a test object, and includes a light collector having a first end formed with a test opening and adapted to be placed in juxtaposition with the test object, a second end, and a light channel extending from the test opening to the second end. A lighting unit is mounted on the light collector, and is operable in order to generate light outputs of different wavelengths. A color filter device is movably disposed in the light collector, and includes a transparent filter and three color filters. A filter-shifting unit is associated with the color filter device, and is operable so as to move the color filter device in the light collector in order to align the filters within the light channel. A photoelectric sensor produces an electric output signal corresponding to the light leaving the color filter device.

Abstract: An image reading method and apparatus enable a high-speed, efficient reading of a multicolor image and a monochromatic image. The image reading apparatus has a color image pickup unit, a first light source and a second light source. An output switching unit selectively switches to either a first output state, where plural kinds of read information from the color image pickup unit are all output as a result of an image reading, or a second output state, where only one kind of read information among the plural kinds of read information from the color image pickup unit is selected to be output as a result of an image reading. A lighting control unit controls lighting conditions of the first light source and the second light source. A switching control unit controls a switching condition of the output switching unit.

Abstract: A first embodiment of the invention includes a light source (1) lighting two parallel optical branches (b1, b2) controlled respectively by two optical shutters (4, 6), one comprising a transparent cell (3) containing a substance to be studied, and the other being used to divert the light from the source. The light coming successively from one and from the other branch is applied selectively to three color filters (F1-F3) filtering three wavelengths selected according to the substance to be studied. The successive luminous intensities which have crossed each of the filters are measured through three detectors (D1 to D3) and the measurings are combined by means of a control (0). Analogous measuring sequences may be achieved with an embodiment comprising three light sources and a single detector. The device can be used for determination of the pH value of a substance.

Abstract: A viewing device for use by an observer to ascertain the authenticity of an instrument of value having an image formed from an optically variable device. The viewing device includes a frame structure which permits viewing of the image in a fixed spatial orientation and a reflector carried by the frame structure for permitting the observer to see simultaneously the image in first and second colors without movement of the observer, the viewing device or the image.

Abstract: Light measurement apparatus includes an elongate member which has at one end thereof light emitter(s) and light detector(s). At least the end of the elongate member that has the light emitter(s) and light detector(s) is surrounded by a resiliently biased sheath. In use, when the elongate member is applied to a surface to take a reading, the sheath defines a light-tight enclosure. A related method for determining intensity and/or color of a colored spot on a surface of a test site uses the light measurement apparatus. The method includes bringing the end of the elongate member into contact with the surface, pressing the resiliently biased sheath towards the surface to define a light-tight enclosure, and measuring the intensity and/or color of the colored spot on the surface.