Method and system for enhanced radiation detection
A radiation detection sensor includes a radiation detector that is segmented into an array of mapping elements, or detectors. The mapping elements may be micro-disposed, such that individual mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map. The mapping elements of the radiation detector may be minimally connected to adjacent radiation detectors, or the mapping elements may be substantially physically isolated from each other.
This application is a continuation-in-part of U.S. patent application Ser. No. 11/005,671 filed Dec. 6, 2004 entitled “Method and System for Enhanced Radiation Detection” by Jorge Roman et al. Priority of the filing date of the prior application is hereby claimed, and the disclosure of the prior application is hereby incorporated by reference.
BACKGROUND1. Field
The present invention relates generally to radiation detection systems and in particular to enhanced resolution radiation detection.
2. Description of the Related Art
Detection of radiation that is emitted from objects and is outside of the visible spectrum can provide useful information. For example, detection systems have been developed for sensing infrared radiation (IR) from an object or source in a target space. Infrared imagers, also called thermal imagers, are instruments that create images of heat instead of light, by converting radiated IR energy to a corresponding map of temperatures or radiance. IR sensing applications including temperature measurement and mapping, forest fire sensing and suppression, and surveillance.
Thermal imaging systems are generally constructed from a variety of different types of infrared detectors. Infrared detectors can be classified as cooled or uncooled. Uncooled detectors include thermal sensors that generate a change in a physical parameter of the detector, such as resistance, due to a change in detector temperature resulting from incident infrared radiation. Cooled detectors include infrared sensors where the change in the physical parameter of the sensor is due to a photoelectron interaction within the material of the sensor.
To detect thermal variation across a target space, thermal imaging systems often use two-dimensional arrays of infrared detectors. In a typical thermal imaging system, the radiation from a target space object will be focused onto a detector array. Electronic or mechanical scanners are generally employed to measure the radiation detected by each detector in the array and thereby produce a two-dimensional display corresponding to a thermal map of the object being imaged. The size and active area of each sensor in the array limits the spatial resolution of the imaging system. Likewise, the need to make electrical connection to the individual detectors, for example to measure a resistance change, can increase system complexity as well as impose constraints on the minimum size for the detectors.
Liquid crystal materials can change color in response to received thermal energy. Typically, liquid crystal materials are used for indicating thermal change and are supplied in film form, or as a coating. In a typical application, a liquid crystal film or coating may be applied to a radiating surface of an object for direct sensing of surface temperature by observing variations in color across the liquid crystal material as a result of the object's surface temperature profile.
Because liquid crystal films are not made up of individual detectors, they do not have the drawback of being limited by a minimum detector size. Also, because liquid crystal films are directly viewed, there is not the need for electrical connections to detect changes in physical parameters. However, liquid crystal films suffer from poor resolution because the thermal energy “bleeds” across the film or coating.
Thus, a need exists for improved methods and apparatus for the detection of radiation emitted from objects. Other problems with the prior art not described above can also be overcome using the teachings of the present invention, as would be readily apparent to one of ordinary skill in the art after reading this disclosure.
SUMMARYEmbodiments disclosed herein address the above stated need of improving detection of radiation emitted from an object. In accordance with the invention, a radiation detection sensor includes a radiation detector that is segmented into an array of mapping elements, or detectors. The mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map. The mapping elements of the radiation detector may be minimally connected to adjacent radiation detectors, or the mapping elements may be substantially physically isolated from each other. The mapping elements may be micro-disposed, such that individual mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map, or material may be removed to provide the segmentation and isolation.
In one exemplary embodiment of a sensor, a focal plane array comprising a radiation detector with mapping elements formed by a substrate with thermal detection material disposed upon it. In this embodiment, the radiation detector is segmented into an array of mapping elements by voids in the substrate and the corresponding thermal detection material. The voids can be formed by removing portions of the substrate and detection material to create “perforations” between adjacent detectors to minimize thermal conduction between detectors within the array. The voids can also be formed by removing portions of the detection material and leaving the underlying substrate substantially unchanged. Alternatively, the voids can be formed using deposition or lithographic techniques so that detection material is disposed or deposited on the substrate only in areas of interest, thereby forming the array of mapping elements, also referred to herein as detectors. The voids between adjacent detectors serves to minimizes thermal conduction between detectors within the array.
Various techniques may be used to remove the thermal material and the substrate. For example, a laser may be used to remove the thermal material after it has been deposited on the substrate. Alternatively, a mask may be placed on the substrate and thermal detection material can be disposed onto the substrate and mask in a deposition or plating operation. The mask is then removed, thereby removing the thermal material in the mask area and leaving behind the voids that define the mapping elements. In addition, various techniques, such as photolithographic techniques and techniques as used in semiconductor fabrication, may also be utilized to form the mapping elements.
In still another exemplary embodiment of a focal plane array sensor, detectors are located in different planes of the sensor. For example, one array of detectors may be located in one plane and another array of detectors may be located in another plane across the array. The two planes may be substantially parallel to each other. Thermal isolation between adjacent detectors may be achieved if adjacent detectors are in different planes.
The focal plane arrays do not need to include a substrate. For example, the mapping elements of the detector can be formed of a thermal detector material and an absorber material, with the absorber material disposed across the thermal detector material in a segmented fashion to define the mapping elements. Alternatively, thermal detector material can be disposed on absorber material in a segmented fashion to define the mapping elements. In other words, a continuous material is simply a means for supporting a segmented layer such that the continuous material and the segmented layer together provide a focal plane array with mapping elements such that individual mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map. Thus, a sensor can be constructed with one or the other of the elements, i.e. thermal detector material or absorber material, performing the supporting function and the other material being segmented.
In addition, while some embodiments describe examples of detectors as including a thermal detector material and an absorber material, the embodiments are not limited to this type of construction. That is, exemplary detectors map one form of energy to another form of energy to provide a visual thermal energy map. For example, a detector may be any device that performs the function of mapping thermal energy to a visual display.
In one exemplary embodiment, a radiation detection sensor includes a thermal conversion material that converts incident radiation into heat energy and also includes a plurality of mapping elements, or detectors, each of which receives heat energy from the thermal conversion material in proximity to the mapping element. A thermal map is produced corresponding to the incident radiation energy received by the sensor, in accordance with sufficiently limited lateral energy dispersion between detectors.
In another exemplary embodiment, a radiation detection sensor includes mapping elements formed with a substrate, and protruding from the top surface of the substrate is an array of columns. The sensor includes radiation detectors having a radiation sensitive layer, such as a radiation sensitive film, and a thermal conversion material, such as an absorber, that may be disposed upon a top surface of the individual columns within the array. The columns provide thermal isolation between the radiation detectors and the substrate. Spatial separation of columns within the array provide thermal and radiant isolation between the radiation detectors upon the tops of individual columns. An array of radiation detectors allows detection, or identification, of the radiation emitted from an object.
In one exemplary embodiment, the radiation detection sensor has a substrate that is planar. In other embodiments, the substrate may be constructed to be a non-planar shape or constructed of a pliable material so that it can be formed to non-planar shapes. For example, the substrate may be shaped or formed to be concave, convex, or other complex surfaces.
In another exemplary embodiment, the radiation detectors include a radiation sensitive layer comprised of a thermochromic liquid crystal (TLC) material and include a thermal conversion material comprised of an infrared absorbing layer disposed on a top most surface. For example, the absorbing layer may comprise black cupric oxide. In this embodiment, the absorbing layer converts radiation that impinges on it into heat that is detected by the TLC radiation sensitive layer.
The radiation detection sensor may also include thermal elements that are used to control the temperature of the substrate. The substrate may be heated or cooled, for example, using heaters/thermoelectric coolers so as to enable biasing of the sensor. In another embodiment, the radiation detection sensor may include thermal shunts. The thermal shunts may be placed at various locations in the radiation detection sensor, for example, the thermal shunts may be located between the substrate and the base of the columns in the array. The thermal shunts may also be located between a source of radiation input and the array of radiation detectors, for example, in the optics used to focus an image of the radiation source onto the array, or in a plane on top of the radiation detectors. The thermal shunts may also be located between the radiation detectors and the column tops.
The thermal shunts may be controllably operable so as to provide a high thermal conductance path, or a low thermal conductance path, between the substrate and the column/sensor element combination or between the source of the radiation and detectors. In one embodiment the thermal shunts may be constructed from thermoelectric cooler material, such as, bismuth telluride or other types of solid state heating/cooling materials. In addition, thermal shunts may be magnetically or electrically alignable carbon nanotubes and ferro-fluids.
The columns of the radiation detection sensor can be various shapes and sizes. For example, in one embodiment the columns are cylinders. In another embodiment a top surface of the column is larger than the base of the column thereby maximizing the amount of incoming radiation that impinges upon an individual detector. The columns can have any desired cross section, for example, circular, oval, square, rectangular, or any other multi-sided polygon shape desired. In addition, there may be multiple detectors supported by a single column or multiple columns may support a single detector. For example, a detector may have a spherical shape and there may be three columns supporting the detector. Other configurations of detectors and support structures may also be used.
An exemplary embodiment of a radiation detection system uses a radiation detection sensor that has multiple radiation mapping elements or radiation detectors. The sensor receives radiated energy emitted by an object and converts the received energy into thermal energy. Then a received thermal energy map of the object is produced.
In one exemplary embodiment, a radiation detection system may include a focal plane array that has a substrate and a plurality of columns protruding from the substrate. Radiation detectors are disposed on tops of the plurality of columns thereby creating an array of radiation detectors. In one embodiment the radiation detectors include a thermochromic liquid crystal material. The system also may include collection optics that focus radiation emitted from an object onto the focal plane array. The system may include imaging optics that focus an image of the focal plane array radiation detectors onto an imaging sensor. The imaging sensor may be a video camera, for example, a CCD camera. The system may also include an illumination source that illuminates the focal plane array. The system may also include an environmental control unit. For example, the environmental control unit may operate to maintain a substrate of the focal plane array at a desired temperature, or vacuum, or humidity level or control any combination of environmental characteristics including magnetic field and electric field environments. The system may also include an image processor configured to accept an output from the imaging sensor.
A null sensor radiation detection system may include a focal plane array that includes a substrate and a plurality of mapping elements disposed in an array on the substrate, wherein radiation detectors are a layer on the mapping elements, thereby creating an array of radiation detectors. The system may also include collection optics that focus radiation emitted from an object onto the focal plane array. In addition, the system may include an illumination source configured to illuminate the focal plane array, and imaging optics that focus an image of the array of detectors onto an imaging sensor. An image processor may be configured to accept and analyze the output from the image sensor and generate a command for a controllable radiation source. The command for the controllable radiation source may cause the controllable radiation source to output radiation that is directed to the focal plane array and maintains the detectors at a predetermined value.
A controllable radiation source may also be used to output a known radiation directed to the focal plane array to characterize the sensitivity and response of detectors with the focal plane array. For example, the focal plane array may be exposed to a constant radiation level, a step change in radiation level, a gradient radiation level, or other variable radiation level. In addition, a target with a known radiation profile may be exposed to the focal plane array. For example a target “shutter” may be placed in front of, or in the entrance pupil, of the radiation detector system and thereby be exposed to the focal plane array. The performance of the detectors within the focal plane array when exposed to a known radiation can be evaluated. For example, the performance characteristics of the detectors, such as sensitivity and response to a step, or varying radiation input can be evaluated.
In another exemplary embodiment of a radiation detection system a target illumination source illuminates, or “paints” an object. Radiation reflected from the object may then be collected by collection optics and focused onto the focal plane array. The target illumination source may be tunable. For example, the target illumination source may include optics or controls to shape the spectrum of the radiation output by the target illumination source. In another example, the target illumination source may include multiple sources, each of which outputs a desired spectrum of radiation. The output of the target illumination source may be mixed, or combined, in any desired combination so that a desired output spectrum is achieved. In this manner the object may be painted with radiation of a desired spectral content which may improve the detection of specific objects.
Other features and advantages of the present invention should be apparent from the following description of exemplary embodiments, which illustrate, by way of example, aspects of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Embodiment described herein are “exemplary” and are not necessarily to be construed as preferred or advantageous over other embodiments.
In accordance with the invention, a radiation detection sensor includes a radiation detector that is segmented into an array of mapping elements, also referred to herein as detectors. The mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map. The radiation detector receives thermal energy and generates the visual thermal energy map, which is provided by the sensor for viewing. The mapping elements of the radiation detector may be minimally connected to adjacent mapping elements, or the mapping elements may be substantially physically isolated from each other. The mapping elements may be micro-disposed, such that individual mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map.
Techniques and apparatus for improved radiation detection are described.
The object 12 may be any object that emits radiation. For example, the object 12 may emit infrared, visible, ultraviolet, Terahertz, or other radiation. The radiation emitted from the source 12 is collected by appropriate collection optics 14. The collection optics 14 may differ depending on the type of radiation desired to be detected. For example, if it is desired to detect infrared radiation, then the collection optics 14 may be configured so as to pass infrared radiation and block other types of radiation. The collection optics 14 can be configured to pass any desired spectrum of radiation that can be focused by the optical means. For example, if the radiation detection system 10 is configured to be operated in a dark environment, such as at night, the collection optics 14 may be configured to focus all radiation onto the focal plane array 16.
The collection optics 14 are well known in the art, and may be one or more of any number of lenses or other optic components. The collection optics 14 produce a focused image of the object 12 onto the focal plane array 16, so that focal plane array 16 may sense the radiant flux emitted by the object 12. The collection optics 14 may include lenses that are made of various types of optical glasses, and optical coatings, to achieve a desired spectral transmittance. The collection optics 14 may also include other types of optical material so that a desired overall spectral transmittance of the collection optics 14 is achieved. In other words, the collection optics 14 may include any device that focuses radiation within a desired spectrum onto the focal plane array 16. For example, for infrared radiation in the range of approximately 0.6 to 21 microns, Zinc Selenium (Zn Se) lenses and windows with antireflective coatings may be used. In addition, the lenses may be of the type piano convex for image formation upon the focal plane array. The collection optics 14 may also include other optical devices, such as, Fresnel lenses, zone plates, pin hole apertures and fish-eye lenses, biconvex, biconcave, and piano concave.
The focal plane array 16, as described in further detail below, includes a plurality of radiation detectors onto which radiation from the object 12 is detected. Each detector within the focal plane array 16 senses a portion of the field of view of the radiation detection system 10. In other words, each individual detector in the focal plane array 16 represents a single pixel, or mapping element, of the radiation detection system 10.
As described further below, in one embodiment of the focal plane array 16, when exposed to radiation, the individual radiation detectors in the array change color in response to the intensity of the radiation incident upon the individual detector. The illumination source 18 illuminates the focal plane array 16 with minimal disturbance to the incoming radiation. For example, in the path between the illumination source 18 and the focal plane array may be placed an optional filter 21. The filter may be configured to block radiation from the illumination source that the detectors within the focal plane array would sense, while passing other radiation. For example, if the detectors are sensitive to heat, the filter 21 may be configured to block infrared radiation but pass other radiation. In one embodiment, the filter 21 may be constructed of glass which substantially blocks infrared radiation so as to minimize any disturbance, or influence, of the illumination source upon the focal plane array detectors that sense infrared radiation, while still allowing the focal plane array to be imaged through the filter 21.
The illumination source 18 may have a broad or a narrow spectral output. In addition, the illumination source may be tunable. In one embodiment, the illumination source 18 may be constructed of one or more narrow band sources so as to be able to enhance specific response ranges of the detectors. That is, the illumination source may have one or more narrow band sources, such as narrow band LEDs, that output a spectrum matched to a specific spectral range of interest in the spectrum of a thermochromic liquid crystal (TLC) detector. For example, a TLC detector may change color from red to yellow to green to blue as its temperature increases in response to radiation incident on an absorber that is converted to thermal energy. If a particular radiance level, corresponding to a particular color of the TLC, is of interest, then the illumination source may be selected or “tuned” to that particular color. In this way, as the TLC changes to the particular color the sensitivity of the readout of the TLC may be improved. For example, if the radiance level of interest corresponds to a TLC color of green, then the illumination source may be tuned to green. When the TLC is red or yellow or blue, the TLC readout will be low because the source illuminating the TLC does not include these colors. When the TLC changes to green the TLC readout will increase because the illumination source matches the TLC color. Because the TLC readout increases, the sensitivity or the ability to detect small color changes, and corresponding radiation level changes, is improved.
The imaging optics 20 focus an image of the focal plane array 16 detectors onto an image sensor 22. The imaging optics 20 are well known in the art, and may be one or more of any number of lenses or other optic components. The imaging optics 20 produce a focused image of the detectors of the focal plane array 16 onto the image sensor 22. The image sensor 22 then produces an output corresponding to an image of the detectors of the focal plane array 16. The image sensor 22 may be, for example, a camera such as a CCD camera. The image produced by the CCD camera may be displayed to a user, or it may be provided to an image processor for further processing.
As illustrated in
In one example, perforations define detectors, or pixels, that are approximately 500 microns in diameter or diagonal size. It is anticipated that the detectors may be much smaller, such as about 50 microns, depending on operating environment, desired energy spectrum of detection, and desired application. The perforations may be produced using a cutting source such as a laser that “burns” the substrate and thermal material to create the voids that provide the segmentation. Smaller detector size may be achieved, in part, using improved power and control of the laser to minimize the detector size. The size of the detector, or pixel, selected for a particular sensor may vary depending on factors such as the sensor operating environment, including the wavelength of the light and/or preconditioning light being used.
The focal plane array can be made of a substrate and detectors. In one example, the detectors include TLC and an absorber. The detector may be applied directly to the substrate, or it may be attached to the substrate using a binder material. In one example, the layers of the focal plane array 16 are deposited, or sprayed on, by starting with a substrate, such as polystyrene, of about 25 microns thickness, then a layer of binder such as PVA, of about 10 microns thickness, next a layer of TLC of about 10 to 30 microns thickness, and then an absorber layer coating of about 10 to 20 microns thickness.
In the example shown in
The perforations thermally isolate the detectors, or pixels, thereby substantially preventing, or minimizing, temperature changes in one detector from affecting the temperature in adjacent detectors. In other words, the detector size and shape may be selected for desired characteristics, for example, selected to provide sufficient pixel thermal isolation for the operating environment, given the anticipated ambient temperature, or the wavelengths being used for conditioning and detecting.
Various techniques can be used to produce the focal plane array 16 as illustrated in
Various techniques can be used to produce the focal plane array 16 as illustrated in
In previous embodiments described above, thermal isolation was achieved, at least in part, by separated detectors in a common plane.
The columns 28 provide physical support for disposing a radiation detector. Each column 28 also provides thermal isolation between the detectors and the substrate 24. The thermal conductance of the column may be selected to be a desired value. For example, it may be desirable for the column to have a low thermal conductance to thereby provide a high thermal isolation between the detectors and the substrate. But, it may also be desirable to have the column thermal conductance high enough so that there is a thermal path from the detector to the substrate 24 allowing the detector to “bleed off” heat to the substrate when a source of radiation causing the detector to heat is removed. In other words, it may be desirable to select the thermal conductance of the column to be a value that allows a desired amount of beat transfer between the radiation detector and the substrate. This technique may also be used to change the response time of the radiation detection sensor to changes in radiation.
As described further below, the location of the columns 28 relative to one another provide radiant and thermal isolation between individual detectors within the array. There are several tradeoffs to consider in the placement of the columns 28. For example, it is desirable to have the detectors close to each other to increase the active area of the focal plane area, the portion of the focal-plane array covered by detectors, so as to increase resolution. However, it is also desirable to have the columns and detectors separated from adjacent columns and detectors to increase isolation between adjacent detectors and reduce “bleeding” of signals between adjacent detectors. “Bleeding” can have the effect of blurring high contrast detail in the image.
In one embodiment, a radiation detection sensor includes a thermal conversion material that converts radiation into heat energy. The sensor also includes a plurality of mapping elements, or detectors, located on the tops of the columns 28 shown in
One embodiment of a radiation detection system using the described radiation detection sensor, includes receiving radiated energy from an object. The received energy is converted into thermal energy. Then a received thermal energy map of the object is produced.
In the embodiment of
In one embodiment, the focal plane array illustrated in
The column 28 provides a low thermal conductance path, i.e. a high thermal isolation path, from the detector 31 to the substrate 24. The low thermal conductance path provides thermal isolation between the detector and the substrate. The separation 64 between the detectors 31, provided by placement of the columns 28, provides thermal and radiant isolation between individual detectors within the focal plane array 16. The thermal and radiant isolation provided by the separation between columns 28 may be provided in many different ways. In one embodiment, the focal plane array 16 can be located within an enclosure that has been evacuated of a substantial portion of air so as to produce a deep vacuum. In another embodiment, the separation 64 between the columns 28 may be made of a low thermal conductance materials, such as, aerogel material.
In another embodiment, the relative positions of the radiation sensitive layer 32 and absorbers 34 may be changed, as illustrated in
The thermal shunt 72 may be constructed of various types of materials. For example, thermoelectric cooler/heater material, such as bismuth telluride, may be used as the substrate 24 with columns made of a low conductance material sitting on top of the substrate 24. The thermal shunt 72 may also be constructed using carbon nanotubes and a ferro-fluid. Operation of the shunt may be controlled in different ways. For example, if the thermal shunt is constructed of a thermoelectric cooler/heater material, it may be controlled by varying a current through the material using typical electrical control circuits, as are well known. If the thermal shunt is constructed of carbon nanotubes and a ferro-fluid, it may be controlled by a controllable magnetic or electric field.
In other embodiments the relative positions of the radiation sensitive layer 32 and absorbers 34 may be changed, as illustrated in
Between the base 74 of the column 28 and the top surface 26 of the substrate 24 there is a thermal shunt 72. As described in relation to
For example, during an initial operation the thermal shunt 72 may be in a high thermal conductance state and thereby provide low thermal isolation between the substrate 24 and the column 28. In this state, the column 28 and detector 31 will reach thermal equilibrium with the substrate 24. As explained further below, the substrate 24 can be controlled to be at a desired temperature. In this manner the detector 31 can be biased to a desired temperature. For example, if the radiation sensitive layer 32 is TLC it can be biased to a desired operating point, such as temperature of red onset for the particular TLC material. After the detector 31 has been biased to a desired operating point the thermal shunt can be operated to change to a state of low thermal conductance and thereby provide a high thermal isolation between the substrate 24 and the column 28.
While the thermal shunt 72 is in its low thermal conductance it will provide a high thermal isolation between the column and the substrate. With the thermal shunt in this state, any radiation that impinges onto the absorber 34 will be converted to heat. Due to the high thermal isolation between the column 28 and the substrate 24, the heat will remain in the absorber and be sensed by the radiation sensitive layer 32. In this manner the amount of radiation impinging on the absorber 34 can be detected. Due to the high thermal isolation, even when momentarily blocking the impinging radiation, the absorber will remain at an elevated temperature and be sensed by the layer 32. It may be desirable to periodically “reset” the detector 31 to the predetermined bias operating point. To “reset” the detector 31, the thermal shunt 72 can be operated to change states so that there is a high thermal conductance path, providing low thermal isolation, between the column 28 and the substrate 24 so that the column 28 and detector 31 return to thermal equilibrium with the substrate. In this manner, the focal plane array 16 can be periodically set to a predetermined operating point.
In another embodiment the relative positions of the radiation sensitive layer 32 and absorbers 34 may be changed, as illustrated in
Thus, in
An image of the detectors of the focal plane array 16 passes through the filter 105 and the beam splitter 102 and is focused onto the image sensor 22 by the imaging lens 104.
Thus, in
The example of
The image processor 124 may be configured to control the illumination source. The image processor may also be configured to control the environmental control unit 122. For example, the image processor 124 may control the environmental control unit 122 so as to bias the focal plane array to a desired operating point.
As illustrated by
In the examples shown in
In the examples illustrated in
An additional aspect of making the focal plane array a concave shape is that the separation 172 between the detectors 31 is decreased, thereby increasing spatial resolution of the focal plane array. In addition, the separation 174 of the support columns 28 is increased, thereby improving isolation between adjacent columns 28.
The shapes of the focal plane array illustrated in
The temperature element 212 may be any type of heating or cooling apparatus that can be controlled. For example, the temperature element 212 may be a thermoelectric cooler, an electric heating element, or other device capable of controlling temperature. The embodiment of
In one embodiment, the focal plane array 16 includes sensing elements, such as TLC. The environmental control unit may be controlled by the image processor 224 to establish a desired bias, or operating point for the focal plane array 16. For example, the environmental control unit 122 may establish a bias point for TLC detectors included on the focal plane array so that the TLC detectors are at red onset. Thus, with no radiation impinging upon the focal plane array, the entire array of sensing elements would be biased to red onset. The elimination of radiation impinging onto the focal plane array may be accomplished in many ways, for example, placing a shutter over the entrance pupil of the null sensor 221, or have thermal shunts located so as to block radiation from impinging on the focal plane array as described above.
After the focal plane array 16 has reached its bias operating point, the controllable radiation source 228 may be commanded to output radiation that is reflected off of the beam splitter 222 so as to impinge upon the focal plane array 16. The radiation from the controllable radiation source 228 that impinges the focal plane array 16 is controlled so as to set the detectors in the focal plane array to a known, desired, operating point. For example, if the detectors include TLC, the controllable radiation source may be commanded by the image processor 224 to input radiation sufficient to set the detectors in the focal plane array to green, or other desired, operating point. It is noted that the controller radiation source 228 may include a scanning mechanism to scan the radiation source output across the focal plane array 16. In other embodiments the scanning mechanism may be separate from the controllable radiation source 228.
During operation of the null sensor 221, as radiation from the object 12 impinges on the focal plane array the detectors that include TLC color will change accordingly. The change in color will be detected at the image sensor 22. The output of the image sensor 22 is connected to the image processor 224 that generates commands to the controllable radiation source to increase or decrease the output of the controllable radiation source as it scans across the focal plane array so that the TLC color remains at its desired operating color, for example green. The signal for controlling the controllable radiation source 228 corresponds to the radiation received from the object 12. The image processor 224 may generate an image corresponding to the control signal and generate a display be presented on the display 226.
The description of
The controllable radiation source 228 may also be used to output a known radiation directed to the focal plane array to characterize, or calibrate, the sensitivity and response of detectors with the focal plane array. For example, the controllable radiation source 228 may be controlled so as to expose the focal plane array 16 to a constant radiation level, a step change in radiation level, a gradient radiation level, or other variable radiation level. In addition, a target with a known radiation profile may be exposed to the focal plane array 16. For example a target “shutter” may be placed in front of, or in the entrance pupil of, the radiation detector system and thereby be exposed to the focal plane array. The performance of the detectors within the focal plane array when exposed to a known radiation can be evaluated. For example, the performance characteristics of the detectors, such as sensitivity and response to a step, or varying radiation input can be evaluated.
In the example shown in
In this manner the object may be painted with radiation of a desired spectral content which may improve the detection of specific objects. For example, if it is desired to identify a particular object, the target illumination source 242 may have its spectral output configured such that radiation that will be reflected from the object of interest will be increased.
The radiation detection system 240 may also include an input filter 244. The input filter may be configured to pass a desired spectrum. For example, the input filter 244 may be configured to have a spectral response, that is pass spectral energy, matched to the spectral output of the target illumination source 242. In another example, the input filter may be configured to have a spectral response that matches a spectral profile of a specific object. The input filter 244 may also be tunable, that is its spectral response may be configurable. In other embodiments, the input filter 244 may include multiple filters that ate individually, or in combination, used to produce the desired spectral response.
For example, if the detectors include TLC, so that the individual detectors change color in relationship to the amount of radiation that impinges on them, then an image of the detector array can be used to map the radiation that was emitted by the object.
In the embodiments described the focal plane array has included a substrate. In other embodiments, the focal plane array does not need to include a substrate. For example, the thermal detector material may be continuous and patches of absorber material may define the detectors. Likewise, an absorber material may be continuous and thermal detector material disposed upon the absorbed thereby defining detectors. In other words, the substrate is simply a means for supporting the detectors, and it is possible to made a focal plane array with one of the other elements, i.e. detector, or absorber, performing the supporting function.
In addition, while some embodiments have described examples of detectors as including a thermal detecting material and an absorbed, they are not limited to this type of detector. That is, exemplary detectors map one form of energy to another form of energy. For example, a detector may be any device that performs the function of mapping thermal energy to a visual display.
In general, a radiation detection sensor can include a radiation detector on a substrate. The radiation detector may be segmented into an array of mapping elements, or detectors, such that individual mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map. The radiation detection sensor may have the radiation detectors within the array of mapping elements minimally connected to adjacent radiation detectors.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A radiation detection sensor comprising:
- a radiation detector that is segmented into an array of mapping elements that are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map; and
- an image sensor that receives the visual thermal energy map and produces a corresponding image.
2. A radiation detection sensor as defined in claim 1, wherein the array of mapping elements comprises mapping elements that are minimally physically connected to adjacent mapping elements.
3. A radiation detection sensor as defined in claim 1, wherein the mapping elements of the radiation detector are formed by a substrate material and a thermal detection material.
4. A radiation detection sensor as defined in claim 3, wherein the mapping elements are defined by voids in portions of the thermal detection material.
5. A radiation detection sensor as defined in claim 4, wherein the voids are formed by perforations in the thermal detection material.
6. A radiation detection sensor as defined in claim 1, wherein the mapping elements are formed with micro-deposition techniques.
7. A radiation detection sensor as defined in claim 1, wherein the mapping elements of the radiation detector comprise a radiation sensitive layer and a thermal conversion material.
8. A radiation detection sensor as defined in claim 7, wherein the radiation sensitive layer is a thermochromic liquid crystal material.
9. A radiation detection sensor as defined in claim 7, wherein the thermal conversion material has high absorptivity and low emissivity.
10. A radiation detection sensor as defined in claim 7, further comprising thermal elements that are used to control a temperature of the substrate.
11. A radiation detection sensor as defined in claim 10, wherein the thermal elements comprise thermoelectric coolers.
12. A radiation detection sensor as defined in claim 10, further comprising an environmental control unit.
13. A radiation detection system, comprising:
- a focal plane array that includes a radiation detector that is segmented into an array of mapping elements such that individual mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map;
- collection optics that focus radiation emitted from an object onto the focal plane array; and
- imaging optics that focus an image of the focal plane array pixels onto an image sensor.
14. A radiation detection system as defined in claim 13, further comprising an image processor configured to accept graphics output from the image sensor and provide an enhanced visual image.
15. A radiation detection system as defined in claim 14, wherein the image processor analyzes the output of the image sensor and generates a command for a controllable radiation source.
16. A radiation detection system as defined in claim 15, wherein the command for the controllable radiation source causes the controllable radiation source to output radiation that is directed to the focal plane array and maintains the mapping elements at a predetermined value.
17. A radiation detection system as defined in claim 13, wherein the image sensor is a camera.
18. A method of detecting radiation emitted from an object, the method comprising:
- focusing radiation emitted from an object onto a focal plane array, wherein the focal plane array includes a radiation detector that is segmented into an array of mapping elements such that individual mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map; and
- focusing an image of the array of detectors onto an imaging sensor thereby producing an image of the visual thermal energy map.
19. An apparatus for detecting radiation emitted from an object; the apparatus comprising:
- means for focusing radiation emitted from an object onto a focal plane array, wherein the focal plane array includes a radiation detector that is segmented into an array of mapping elements such that individual mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map; and
- means for focusing an image of the array of detectors onto an imaging sensor thereby producing an image of the visual thermal energy map.
20. A method of producing a radiation detection sensor, the method comprising:
- providing a thermal detection material; and
- segmenting the thermal detection material into an array of mapping elements that are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map.
21. A method as defined in claim 20, wherein segmenting comprises removal of portions of the thermal detection material.
22. A method as defined in claim 20, wherein the thermal detection material includes a radiation detector material and substrate.
23. A method as defined in claim 20, wherein segmenting comprises removing portions of the thermal detection material.
24. A method as defined in claim 20, wherein segmenting comprises micro-disposing thermal detection material into pixel-sized portions.
25. A method as defined in claim 24, wherein segmenting comprises photolithography processing.
26. A method as defined in claim 25, wherein segmenting comprises depositing radiation detector material onto a substrate.
27. An apparatus for producing a radiation detection sensor, the apparatus comprising:
- means for disposing a radiation detector material onto a substrate; and
- means for segmenting the radiation detector material into an array of mapping elements that are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map.
28. A method of producing a radiation detector, the method comprising segmenting a radiation detector material into an array of mapping elements such that individual mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map.
Type: Application
Filed: Dec 6, 2005
Publication Date: Oct 12, 2006
Inventors: Jorge Roman (Carlsbad, CA), Gregory Schmidt (Encinitas, CA), Mary Schmidt (Encinitas, CA), William Schmidt (Encinitas, CA), Robert Fryer (Solana Beach, CA), Henri Sasmor (Oceanside, CA)
Application Number: 11/296,132
International Classification: G01J 5/48 (20060101);