WO2009156362A1 - Imaging apparatus and method - Google Patents

Imaging apparatus and method Download PDF

Info

Publication number
WO2009156362A1
WO2009156362A1 PCT/EP2009/057730 EP2009057730W WO2009156362A1 WO 2009156362 A1 WO2009156362 A1 WO 2009156362A1 EP 2009057730 W EP2009057730 W EP 2009057730W WO 2009156362 A1 WO2009156362 A1 WO 2009156362A1
Authority
WO
WIPO (PCT)
Prior art keywords
polarisation
detector elements
wavelength
differently
sensitive
Prior art date
Application number
PCT/EP2009/057730
Other languages
French (fr)
Inventor
Robert Craig
Stephen Mcgeoch
John F Parsons
Original Assignee
Thales Holdings Uk Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thales Holdings Uk Plc filed Critical Thales Holdings Uk Plc
Priority to EP09769211A priority Critical patent/EP2301243A1/en
Publication of WO2009156362A1 publication Critical patent/WO2009156362A1/en

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/30—Transforming light or analogous information into electric information
    • H04N5/33—Transforming infrared radiation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G01J3/0224—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using polarising or depolarising elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/30—Measuring the intensity of spectral lines directly on the spectrum itself
    • G01J3/36—Investigating two or more bands of a spectrum by separate detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/58—Radiation pyrometry, e.g. infrared or optical thermometry using absorption; using extinction effect
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0216—Coatings
    • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/02162—Coatings for devices characterised by at least one potential jump barrier or surface barrier for filtering or shielding light, e.g. multicolour filters for photodetectors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/10—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from different wavelengths
    • H04N23/11—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from different wavelengths for generating image signals from visible and infrared light wavelengths
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/48—Increasing resolution by shifting the sensor relative to the scene
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14643—Photodiode arrays; MOS imagers
    • H01L27/14649—Infrared imagers

Definitions

  • This present invention relates to the field of infra-red sensors, for example infrared detectors or thermal imagers, and is particularly concerned with the field of discriminative imaging.
  • thermal imagers generally provide good contrast between objects of interest such as humans or vehicles and background and this usually allows the objects to be detected and identified based upon shape, for example by thermal signature.
  • objects of interest have much lower contrast, or their shape may be obscured, and some backgrounds have a high level of clutter. All of these effects limit the effectiveness of discrimination of objects of interest in thermal images.
  • Objects of interest in a scene can be identified by the polarisation of light or infrared radiation emitted or reflected by them.
  • the polarisation characteristics of an object are strongly dependent on the texture of the surface of the object.
  • Objects can also be distinguished by the spectral content of the radiation emitted or reflected by them.
  • the spectral characteristics of an object are usually dependent on the material composition of the object.
  • a particular problem is the detection of disturbed earth, which is a typical feature indicative of buried munitions.
  • disturbed earth is a typical feature indicative of buried munitions.
  • an area of disturbed earth does not typically have a well defined shape or size and is also difficult to distinguish from the background using known techniques.
  • a detector comprising a plurality of detector elements, the plurality of detector elements comprising a plurality of differently polarisation-sensitive detector elements and a plurality of differently wavelength-sensitive detector elements.
  • radiation of different polarisations and radiation of different wavelengths may be detected using the same detector.
  • Discrimination can be improved by combining different sensor modalities to get more information about the scene being imaged.
  • the plurality of detector elements is preferably arranged in an array, preferably a two-dimensional array.
  • the array may comprise a plurality of non-overlapping sub-arrays, and preferably each sub-array comprises at least two differently polarisation sensitive detector elements and at least two differently polarisation wavelength sensitive detector elements.
  • Each sub-array may be a square or rectangular sub-array and preferably each sub-array has a substantially identical arrangement of detector elements to each other sub-array.
  • an imaging apparatus for imaging a scene comprising the detector, and means for directing radiation from the scene to form an image at the array.
  • the apparatus may simultaneously capture spatially-registered thermal, polarimetric and spectral imagery.
  • the images can be processed to detect objects of interest with increased probability of detection, or lower false alarm rate, than for any of the modalities (thermal, polarimetric, spectral) individually.
  • the at least two differently polarisation sensitive detector elements are preferably two differently polarisation sensitive detector elements that have substantially the same wavelength sensitivity, or four differently sensitive polarisation detector elements that have substantially the same wavelength sensitivity.
  • the at least two differently polarisation sensitive detector elements may comprise one detector element sensitive to a polarisation substantially equal to 0° and one detector element sensitive to a polarisation substantially equal to 90°.
  • the polarisations may be defined relative to each other or may be defined relative to an object or scene under investigation. Preferably the polarisations are defined relative to the ground. It has been found that for most land scenes most of the information is contained in the polarisation vectors horizontal and vertical to the land surface, and thus two rather than four differently polarisation sensitive detector elements may produce useful results.
  • the at least two differently polarisation sensitive detector elements have a sensitivity that has a maximum as a function of wavelength at a frequency substantially equal to 9.1 ⁇ m. It has been found that the SiO 2 absorption band has a maximum around 9.1 ⁇ m and so use of that wavelength is particularly useful in detecting the presence of disturbed soil, as soil contains a significant amount of SiO 2 .
  • the apparatus may be particularly suitable for detecting or imaging disturbed earth, which may be associated with buried munitions or other objects. It has been found that disturbed earth may be at a different temperature from surrounding terrain and this can be detected with a thermal imager. It has also been found that the false alarm rate for detection of disturbed earth (for instance due to other temperature and emissivity variations in the background) may be reduced by using polahmetric imaging to discriminate the disturbed earth from its surroundings based upon difference in its texture. Furthermore, it has been found that disturbed earth can be discriminated by its spectral response. This arises from the strong absorption feature at about 9.2 ⁇ m due to silicates in the earth. For disturbed soil, this feature is reduced.
  • disturbed soil can be discriminated by spectral imaging using a waveband at the absorption feature and another (or more than one other) in a different part of the spectrum.
  • the apparatus is able to provide a combination of infrared, spectral and polahmetric imaging and thus may be particularly effective at detecting or imaging disturbed earth.
  • detection apparatus for detecting the presence of disturbed soil, comprising detection means sensitive to radiation having a wavelength substantially equal to 9.1 ⁇ m.
  • detection means sensitive to radiation having a wavelength substantially equal to 9.1 ⁇ m.
  • the detection means has maximum sensitivity to radiation having a wavelength substantially equal to 9.1 ⁇ m.
  • the at least two differently wavelength sensitive detector elements may comprise at least one detector element that is distinct from the at least two differently polarisation sensitive detector elements.
  • the at least one detector element that is distinct from the at least two differently polarisation sensitive detector elements preferably has a polarisation sensitivity that is different from the polarisation sensitivity of either of the at least two differently polarisation sensitive detector elements, and preferably has a polarisation sensitivity substantially equal to 45°.
  • the at least two differently wavelength sensitive detector elements may be two detector elements distinct from the at least two differently polarisation sensitive detector elements.
  • the at least two differently wavelength sensitive detector elements have different wavelength sensitivities to each other and/or to the at least two differently polarisation sensitive detector elements.
  • each of the at least two differently wavelength sensitive detector elements has a sensitivity that have a maximum as a function of wavelength at a frequency substantially equal to one of 8 ⁇ m, 9 ⁇ m and 10 ⁇ m, preferably substantially equal to one of 8.2 ⁇ m, 9.1 ⁇ m and 10.4 ⁇ m
  • the apparatus preferably comprises processing means for processing and/or comparing response signals from the detection elements.
  • the processing means is configured to compare response signals from the differently polarisation sensitive detection elements and to compare response signals from the differently wavelength sensitive detection elements.
  • the apparatus preferably further comprises means for causing relative movement of the image and the array, configured such that in operation the image and the array are placed in a series of relative positions.
  • the apparatus is configured to provide accurately registered images in at least two, and up to four polarisation directions (four directions are sufficient to allow calculation of all the linear polarisation information of the radiation).
  • the apparatus is configured to also provide up to three spectrally distinct images.
  • the means for causing relative movement may be configured to cause relative movement in a repetitive cycle.
  • the placement in a series of relative positions of the image and the array, and/or the direction of the at least one image portion to a respective series of detector elements in turn, may be repeated.
  • each relative position is preferably maintained during a detection interval, and each detector element may generate a response signal during each detection interval.
  • the apparatus further comprises storage means for storing, for each detector element, the respective response signal generated during each detection interval.
  • a portion of an image is directed to a detector element, it may be understood that the portion of the image wholly or partially overlaps the detector element.
  • Each series of detector elements usually includes at least one detector element that is also included in at least one other of the series of detector elements.
  • every detector element in the series is also included in at least one other of the series of detector elements.
  • each detector element is included in each of a plurality of the series of detector elements.
  • each series of detector elements comprises the or a plurality of differently polarisation sensitive detection elements and the or a plurality of differently wavelength sensitive detection elements.
  • Each series of detector elements preferably comprises a plurality of adjacent detector elements.
  • each detector element in the series may be adjacent to the immediately preceding detector element in the series.
  • an adjacent detector element may be meant the nearest neighbour in the x or y direction or in a direction at 45° or 135° to the x and/or y direction in the x-y plane.
  • Each series of detector elements may comprise two detector elements.
  • each series of detector elements comprises three or four detector elements.
  • the array of detector elements may be located substantially at the focal plane of the directing means, such that the image is substantially in focus, and each portion of the image may correspond to a respective part of the scene to be imaged, in a one-to-one relationship.
  • the radiation preferably comprises infrared radiation, in particular far infrared radiation.
  • a detector element having a particular polarisation sensitivity may be considered to be a detector element have a maximum sensitivity to radiation having a particular polarisation direction.
  • a detector element being sensitive to a particular wavelength may be considered to be a detector element having a maximum sensitivity to radiation substantially equal to that particular wavelength.
  • each detector element comprises a quantum well device, preferably a quantum well infra-red photodetector (QWIP).
  • QWIP quantum well infra-red photodetector
  • the apparatus preferably further comprises means for obtaining response signals from the detector elements, preferably for each of the relative positions.
  • Each detector element may comprise a photo-sensitive detection area, and electrical connections to the detection area which may be used to read response signals from the detection area.
  • a method of imaging a scene comprising detecting radiation at each of a plurality of different polarisations and detecting radiation at each of a plurality of different wavelengths and generating image data representative of at least one polarisation-dependent image and at least one wavelength-dependent image in dependence on the detected radiation.
  • the at least one polarisation- dependent image and at least one wavelength-dependent image may be a combined image.
  • a discriminative IR imager based on a micro-scanned QWIP detector array that combines polarisation and spectral functionality in a single device.
  • the imager is preferably suitable for either or both day and night operation.
  • Figure 1 is an illustration of an imaging apparatus according to the preferred embodiment
  • Figure 2 is an illustration of a polarisation- and wavelength-sensitive detector array included in the apparatus of Figure 1 ;
  • Figure 3 is an illustration of the movement of a single image portion, or pixel, on the detector array in one cycle of operation of the apparatus of Figures 1 and 2.
  • Figure 1 shows a side-view of an imaging apparatus according to the preferred embodiment, in the form of a thermal camera.
  • the apparatus includes an optical system comprising an arrangement of lenses and mirrors 2 4 6 8 aligned with a microscanner 10, and a detector array 12 comprising a two-dimensional array of detector elements.
  • the microscanner 10 is linked to a control processor, or processing electronics, 14 that controls movement of the microscanner in operation.
  • the detector array 12 is connected to the control processor or processing electronics 14, which in operation stores and processes response signals from the detector elements.
  • the arrangement of lenses and mirrors 2 4 6 8 is aligned with a scene to be imaged, along the line of sight of the apparatus and, in operation, infra-red radiation from the scene passes through the arrangement of lenses and mirrors 2 4 6 and the microscanner 10 and forms an image on the detector array 12.
  • Part of the detector array 12 is shown in plan view in Figure 2, and comprises a two-dimensional array of detector elements 20 22 24 26, with different elements being sensitive to different directions of polarisation and/or different wavelengths arranged in a repeating pattern of four in a checkerboard pattern.
  • Each repeating pattern of four detector elements 20 22 24 26 can be considered to be a sub-array.
  • the spectral sensitivity of the detector elements is chosen to maximise the visibility of the SiO 2 absorption band, with the aim of detecting and/or imaging disturbed soil, leading to detection of mines and IEDs, and the detector elements 20 22 24 26 of each sub-array have polarisation and wavelength characteristics as follows:- [0 ⁇ A,
  • the numbers 0, 45, 90 represent polarisation sensitivities of 0° 45° and 90° respectively.
  • the symbols ⁇ A , ⁇ B and ⁇ c represent the wavelength of maximum sensitivity of the detector element. In this example, ⁇ A is centred at 9.2 ⁇ m to coincide with the silicate absorption feature and ⁇ B and ⁇ c are centred at 8.1 ⁇ m and 10.4 ⁇ m respectively.
  • the three wavelength bands allow the collection of most of the radiation transmitted in the long wavelength infra-red (LWIR) atmospheric window.
  • LWIR long wavelength infra-red
  • the performance of the apparatus is better than that of an apparatus based upon a two waveband scheme as it allows the comparison of the response at the silicate absorption feature (centred at 9.2 ⁇ m) with two other wavebands (centred at 8.1 ⁇ m and 10.4 ⁇ m).
  • the use of detector elements sensitive to polarisations of 0° and 90° for the wavelength band of interest is to maximise the response from typical land targets and objects of interest.
  • the use of detector elements sensitive to a polarisation of 45° in the reference wavebands is chosen to minimise the effect of polarisation without going to the expense of producing a non-polarised response.
  • the signals of each set of similarly-sensitive elements form separate images, for example separate video images. After one frame of four fields, information for every scene pixel for each of the four element types is available.
  • Polarisation contrast imaging requires two images with mutually orthogonal polarisation sensitivities. Four images are required to collect all of the linear polarisation components, but experiment has shown that, for most land scenes, most of the information is contained in the pair of images with polarisation vectors horizontal and vertical to the land surface. The images which collect the polarisation data should be in the same waveband for best results.
  • one of the other detector elements in each two-by-two block or sub-array should be at a different waveband from the pair of detector elements collecting the polarisation data. That detector element can be polarisation sensitive or not.
  • the fourth detector element in the block or sub-array can be at the same waveband as one of the others, or a different one; it can be polarisation sensitive or not.
  • first oblique, vertical and second oblique polarisation sensitivities as 0, 45, 90 & 135, and wavebands as ⁇ A , ⁇ B , and ⁇ c
  • a block comprising [0 ⁇ A , 90 ⁇ A , 0 ⁇ B , 90 ⁇ B ] would allow discrimination of spectral features with contrast between ⁇ A and ⁇ B and would also measure horizontal-vertical polarisation contrast.
  • detector elements which have no polarisation sensitivity. It should be noted that it is in general more complex and expensive to fabricate a mixture of polarisation sensitive and insensitive elements.
  • Each detector element in the preferred embodiment comprises a quantum well infra-red photodetector (QWIP).
  • QWIPs require diffraction grating structures on the detector elements in order to make the angle of radiation propagation within the detector element match the QWIP structure. If a linear diffraction grating is used, the QWIP provides a polarisation-sensitive response.
  • each of the QWIPs includes a linear diffraction grating positioned in front of a detection area, and the polarisation sensitivity of each QWIP is determined by the angle of its linear diffraction grating. The spectral response of each QWIP is selected by selecting the pitch of the diffraction grating. It is possible to further tune the spectral response using the design of the QWIP structure.
  • the microscanner 10 comprises a mirror and associated piezo-electhc actuators that are operable to drive the lens by selected distances in a series of steps. Each movement of the lens causes a movement of the image relative to the array.
  • the microscanner 8 drives the mirror such as to cause movements of the image relative to the array.
  • the microscanner 8 moves the image in a cyclic series of four positions, separated by steps corresponding to the pitch step of the detector array
  • each image portion made up of radiation from a corresponding scene point or region
  • each image portion is held stationary over a detector element of each of the four different types of polarisation sensitivity in turn.
  • the array and image are moved so that the same image portion is directed to a detector element of each different polarisation sensitivity type, it is ensured that images produced using the detector elements of each different type are in registration with each other.
  • the image is held stationary at each of the four positions relative to the array during a detection interval, or integration time, between movements.
  • Each detector element of the array detects and integrates received radiation during the integration time.
  • the integration is simultaneous for every detector element of the array, and each detector element produces an electrical signal corresponding to the integrated amount of radiation for that detector element.
  • the electrical signals of the detector elements are read out by the control processor at the end of the integration time, to produce a field of data, comprising a response signal, or pixel signal, in respect of each detector element.
  • the displacement cycle begins with the image portion or pixel 30 being aligned with one of the detector elements 20 and held for the integration and read out time.
  • the image portion is then moved, and held for the integration and read out time, over each of the detector elements 22 24 and 26 in turn, before returning to the detector element 20 to complete a single displacement cycle.
  • the displacement cycle is then be repeated a desired number of times.
  • the control processor processes the four successive fields of data generated during each displacement cycle in dependence on the polarisation sensitivity and wavelength sensitivity of the detector elements. Registered polarisation- and wavelength-dependent images are obtained by comparison of the fields of data.
  • the apparatus of the preferred embodiment can be used as a "colour" camera.
  • three colours and two directions of polarisation are provided in each sub-array. The image is moved so that each part is sampled by each of the detector types.
  • microscanner mechanisms are used in place of the piezoelectric actuator and mirror arrangement described above.
  • a tilting plate or moving lens may be used instead of a tilting mirror.
  • the detector array itself rather than the radiation forming the image, may be displaced.

Abstract

An infrared detector comprising a plurality of detector elements, the plurality of detector elements comprising a plurality of differently polarisation-sensitive detector elements and a plurality of differently wavelength-sensitive detector elements.

Description

Imaging apparatus and method
This present invention relates to the field of infra-red sensors, for example infrared detectors or thermal imagers, and is particularly concerned with the field of discriminative imaging.
Known thermal imagers generally provide good contrast between objects of interest such as humans or vehicles and background and this usually allows the objects to be detected and identified based upon shape, for example by thermal signature. However, some objects of interest have much lower contrast, or their shape may be obscured, and some backgrounds have a high level of clutter. All of these effects limit the effectiveness of discrimination of objects of interest in thermal images.
Objects of interest in a scene (particularly man-made objects) can be identified by the polarisation of light or infrared radiation emitted or reflected by them. The polarisation characteristics of an object are strongly dependent on the texture of the surface of the object. Objects can also be distinguished by the spectral content of the radiation emitted or reflected by them. The spectral characteristics of an object are usually dependent on the material composition of the object.
These identification techniques are facilitated if images of the scene for several directions of polarisation and in different spectral wavebands can be produced which are accurately registered in position.
Individual imaging sensors often do not provide enough information to discriminate objects of interest in the field of view for a number of reasons, including insufficient contrast, insufficient resolution, the presence of only an incomplete image of the object (for instance if the object is partly hidden) and the presence of clutter (such as background features that resemble the object of interest). Those problems apply both to automatic target detection and to systems with a human operator.
A particular problem is the detection of disturbed earth, which is a typical feature indicative of buried munitions. For example, an area of disturbed earth does not typically have a well defined shape or size and is also difficult to distinguish from the background using known techniques.
In a first independent aspect of the invention there is provided a detector comprising a plurality of detector elements, the plurality of detector elements comprising a plurality of differently polarisation-sensitive detector elements and a plurality of differently wavelength-sensitive detector elements.
Thus, radiation of different polarisations and radiation of different wavelengths may be detected using the same detector. Discrimination can be improved by combining different sensor modalities to get more information about the scene being imaged.
The plurality of detector elements is preferably arranged in an array, preferably a two-dimensional array. The array may comprise a plurality of non-overlapping sub-arrays, and preferably each sub-array comprises at least two differently polarisation sensitive detector elements and at least two differently polarisation wavelength sensitive detector elements.
Each sub-array may be a square or rectangular sub-array and preferably each sub-array has a substantially identical arrangement of detector elements to each other sub-array. In a further independent aspect of the invention there is provided an imaging apparatus for imaging a scene, the apparatus comprising the detector, and means for directing radiation from the scene to form an image at the array.
Thus a combination of simultaneous spectral and polahmethc imaging can be provided, which can be used to provide better discrimination than either spectral or polarimetric thermal imaging alone.
The apparatus may simultaneously capture spatially-registered thermal, polarimetric and spectral imagery. The images can be processed to detect objects of interest with increased probability of detection, or lower false alarm rate, than for any of the modalities (thermal, polarimetric, spectral) individually.
The at least two differently polarisation sensitive detector elements are preferably two differently polarisation sensitive detector elements that have substantially the same wavelength sensitivity, or four differently sensitive polarisation detector elements that have substantially the same wavelength sensitivity.
Four differently sensitive polarisation sensitive detector elements are required if all linear polarisation components are to be determined exactly.
The at least two differently polarisation sensitive detector elements may comprise one detector element sensitive to a polarisation substantially equal to 0° and one detector element sensitive to a polarisation substantially equal to 90°. The polarisations may be defined relative to each other or may be defined relative to an object or scene under investigation. Preferably the polarisations are defined relative to the ground. It has been found that for most land scenes most of the information is contained in the polarisation vectors horizontal and vertical to the land surface, and thus two rather than four differently polarisation sensitive detector elements may produce useful results.
Preferably the at least two differently polarisation sensitive detector elements have a sensitivity that has a maximum as a function of wavelength at a frequency substantially equal to 9.1 μm. It has been found that the SiO2 absorption band has a maximum around 9.1 μm and so use of that wavelength is particularly useful in detecting the presence of disturbed soil, as soil contains a significant amount of SiO2.
Thus, the apparatus may be particularly suitable for detecting or imaging disturbed earth, which may be associated with buried munitions or other objects. It has been found that disturbed earth may be at a different temperature from surrounding terrain and this can be detected with a thermal imager. It has also been found that the false alarm rate for detection of disturbed earth (for instance due to other temperature and emissivity variations in the background) may be reduced by using polahmetric imaging to discriminate the disturbed earth from its surroundings based upon difference in its texture. Furthermore, it has been found that disturbed earth can be discriminated by its spectral response. This arises from the strong absorption feature at about 9.2μm due to silicates in the earth. For disturbed soil, this feature is reduced. Thus, disturbed soil can be discriminated by spectral imaging using a waveband at the absorption feature and another (or more than one other) in a different part of the spectrum. The apparatus is able to provide a combination of infrared, spectral and polahmetric imaging and thus may be particularly effective at detecting or imaging disturbed earth.
That feature is particularly important and so in another independent aspect there is provided detection apparatus for detecting the presence of disturbed soil, comprising detection means sensitive to radiation having a wavelength substantially equal to 9.1 μm. Preferably the detection means has maximum sensitivity to radiation having a wavelength substantially equal to 9.1 μm.
The at least two differently wavelength sensitive detector elements may comprise at least one detector element that is distinct from the at least two differently polarisation sensitive detector elements. The at least one detector element that is distinct from the at least two differently polarisation sensitive detector elements preferably has a polarisation sensitivity that is different from the polarisation sensitivity of either of the at least two differently polarisation sensitive detector elements, and preferably has a polarisation sensitivity substantially equal to 45°.
The at least two differently wavelength sensitive detector elements may be two detector elements distinct from the at least two differently polarisation sensitive detector elements. Preferably the at least two differently wavelength sensitive detector elements have different wavelength sensitivities to each other and/or to the at least two differently polarisation sensitive detector elements.
Preferably each of the at least two differently wavelength sensitive detector elements has a sensitivity that have a maximum as a function of wavelength at a frequency substantially equal to one of 8μm, 9 μm and 10 μm, preferably substantially equal to one of 8.2μm, 9.1 μm and 10.4μm
The apparatus preferably comprises processing means for processing and/or comparing response signals from the detection elements. Preferably the processing means is configured to compare response signals from the differently polarisation sensitive detection elements and to compare response signals from the differently wavelength sensitive detection elements. The apparatus preferably further comprises means for causing relative movement of the image and the array, configured such that in operation the image and the array are placed in a series of relative positions.
By providing the means for causing relative movement, it can be ensured that the same portion or portions of the image can be directed to detector elements having different polarisation sensitivities and different wavelength sensitivities, in turn enabling measurement of the relative amounts of radiation of different polarisations and different wavelengths emitted by any given part of the scene.
It is therefore possible to obtain both polarisation-dependent and wavelength- dependent representations of the image of the scene that are in spatial registration with each other.
Preferably the apparatus is configured to provide accurately registered images in at least two, and up to four polarisation directions (four directions are sufficient to allow calculation of all the linear polarisation information of the radiation). In one configuration, the apparatus is configured to also provide up to three spectrally distinct images.
The means for causing relative movement may be configured to cause relative movement in a repetitive cycle. Thus, the placement in a series of relative positions of the image and the array, and/or the direction of the at least one image portion to a respective series of detector elements in turn, may be repeated.
In operation, the image and the array are preferably placed in each of the relative positions of the series in turn, each relative position is preferably maintained during a detection interval, and each detector element may generate a response signal during each detection interval. Preferably the apparatus further comprises storage means for storing, for each detector element, the respective response signal generated during each detection interval.
If a portion of an image is directed to a detector element, it may be understood that the portion of the image wholly or partially overlaps the detector element.
Each series of detector elements usually includes at least one detector element that is also included in at least one other of the series of detector elements. Preferably, for each series of detector elements, every detector element in the series is also included in at least one other of the series of detector elements. Preferably each detector element is included in each of a plurality of the series of detector elements.
Preferably each series of detector elements comprises the or a plurality of differently polarisation sensitive detection elements and the or a plurality of differently wavelength sensitive detection elements.
Each series of detector elements preferably comprises a plurality of adjacent detector elements. For each series of detector elements, each detector element in the series may be adjacent to the immediately preceding detector element in the series. By an adjacent detector element may be meant the nearest neighbour in the x or y direction or in a direction at 45° or 135° to the x and/or y direction in the x-y plane. Each series of detector elements may comprise two detector elements. Preferably each series of detector elements comprises three or four detector elements.
The array of detector elements may be located substantially at the focal plane of the directing means, such that the image is substantially in focus, and each portion of the image may correspond to a respective part of the scene to be imaged, in a one-to-one relationship. The radiation preferably comprises infrared radiation, in particular far infrared radiation.
A detector element having a particular polarisation sensitivity may be considered to be a detector element have a maximum sensitivity to radiation having a particular polarisation direction.
A detector element being sensitive to a particular wavelength may be considered to be a detector element having a maximum sensitivity to radiation substantially equal to that particular wavelength.
Preferably each detector element comprises a quantum well device, preferably a quantum well infra-red photodetector (QWIP).
The apparatus preferably further comprises means for obtaining response signals from the detector elements, preferably for each of the relative positions. Each detector element may comprise a photo-sensitive detection area, and electrical connections to the detection area which may be used to read response signals from the detection area.
In another independent aspect of the invention there is provided a method of imaging a scene comprising detecting radiation at each of a plurality of different polarisations and detecting radiation at each of a plurality of different wavelengths and generating image data representative of at least one polarisation-dependent image and at least one wavelength-dependent image in dependence on the detected radiation. The at least one polarisation- dependent image and at least one wavelength-dependent image may be a combined image.
In another independent aspect there is provided a method of detecting the presence of disturbed soil by detecting radiation having a wavelength substantially equal to 9.1 μm and determining the presence of disturbed soil in dependence on the detected radiation.
In a further independent aspect there is provided a discriminative IR imager based on a micro-scanned QWIP detector array that combines polarisation and spectral functionality in a single device. The imager is preferably suitable for either or both day and night operation.
In a further independent aspect, there is provided apparatus substantially as described herein, with reference to one or more of the accompanying drawings.
In another independent aspect, there is provided a method substantially as described herein, with reference to one or more of the accompanying drawings.
Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, apparatus features may be applied to method features and vice versa.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Figure 1 is an illustration of an imaging apparatus according to the preferred embodiment;
Figure 2 is an illustration of a polarisation- and wavelength-sensitive detector array included in the apparatus of Figure 1 ; and
Figure 3 is an illustration of the movement of a single image portion, or pixel, on the detector array in one cycle of operation of the apparatus of Figures 1 and 2. Figure 1 shows a side-view of an imaging apparatus according to the preferred embodiment, in the form of a thermal camera. The apparatus includes an optical system comprising an arrangement of lenses and mirrors 2 4 6 8 aligned with a microscanner 10, and a detector array 12 comprising a two-dimensional array of detector elements. The microscanner 10 is linked to a control processor, or processing electronics, 14 that controls movement of the microscanner in operation. The detector array 12 is connected to the control processor or processing electronics 14, which in operation stores and processes response signals from the detector elements.
The arrangement of lenses and mirrors 2 4 6 8 is aligned with a scene to be imaged, along the line of sight of the apparatus and, in operation, infra-red radiation from the scene passes through the arrangement of lenses and mirrors 2 4 6 and the microscanner 10 and forms an image on the detector array 12.
Part of the detector array 12 is shown in plan view in Figure 2, and comprises a two-dimensional array of detector elements 20 22 24 26, with different elements being sensitive to different directions of polarisation and/or different wavelengths arranged in a repeating pattern of four in a checkerboard pattern. Each repeating pattern of four detector elements 20 22 24 26 can be considered to be a sub-array.
In the preferred embodiment of Figures 1 and 2 the spectral sensitivity of the detector elements is chosen to maximise the visibility of the SiO2 absorption band, with the aim of detecting and/or imaging disturbed soil, leading to detection of mines and IEDs, and the detector elements 20 22 24 26 of each sub-array have polarisation and wavelength characteristics as follows:- [0λA,
90λA, 45λB, 45λc]. The numbers 0, 45, 90 represent polarisation sensitivities of 0° 45° and 90° respectively. The symbols λA, λB and λc represent the wavelength of maximum sensitivity of the detector element. In this example, λA is centred at 9.2μm to coincide with the silicate absorption feature and λB and λc are centred at 8.1 μm and 10.4μm respectively. The three wavelength bands allow the collection of most of the radiation transmitted in the long wavelength infra-red (LWIR) atmospheric window. The performance of the apparatus is better than that of an apparatus based upon a two waveband scheme as it allows the comparison of the response at the silicate absorption feature (centred at 9.2μm) with two other wavebands (centred at 8.1 μm and 10.4μm). The use of detector elements sensitive to polarisations of 0° and 90° for the wavelength band of interest (centred at 9.2μm in this example) is to maximise the response from typical land targets and objects of interest. The use of detector elements sensitive to a polarisation of 45° in the reference wavebands (centred at 8.1 μm and 10.4μm in this example) is chosen to minimise the effect of polarisation without going to the expense of producing a non-polarised response.
The signals of each set of similarly-sensitive elements form separate images, for example separate video images. After one frame of four fields, information for every scene pixel for each of the four element types is available.
Other combinations of polarisation and wavelength sensitivities of the detector elements are used in alternative embodiments, depending on the intended application.
Polarisation contrast imaging requires two images with mutually orthogonal polarisation sensitivities. Four images are required to collect all of the linear polarisation components, but experiment has shown that, for most land scenes, most of the information is contained in the pair of images with polarisation vectors horizontal and vertical to the land surface. The images which collect the polarisation data should be in the same waveband for best results.
For multi-spectral polahmetric imaging, one of the other detector elements in each two-by-two block or sub-array should be at a different waveband from the pair of detector elements collecting the polarisation data. That detector element can be polarisation sensitive or not. The fourth detector element in the block or sub-array can be at the same waveband as one of the others, or a different one; it can be polarisation sensitive or not.
If we denote horizontal, first oblique, vertical and second oblique polarisation sensitivities as 0, 45, 90 & 135, and wavebands as λA, λB, and λc , then there are numerous combinations which can be chosen according to the task for which the sensor is to be used. For example, a block comprising [0λA, 90 λA, 0 λB, 90 λB] would allow discrimination of spectral features with contrast between λA and λB and would also measure horizontal-vertical polarisation contrast. It is also possible to have detector elements which have no polarisation sensitivity. It should be noted that it is in general more complex and expensive to fabricate a mixture of polarisation sensitive and insensitive elements.
Each detector element in the preferred embodiment comprises a quantum well infra-red photodetector (QWIP). QWIPs require diffraction grating structures on the detector elements in order to make the angle of radiation propagation within the detector element match the QWIP structure. If a linear diffraction grating is used, the QWIP provides a polarisation-sensitive response. In the preferred embodiment, each of the QWIPs includes a linear diffraction grating positioned in front of a detection area, and the polarisation sensitivity of each QWIP is determined by the angle of its linear diffraction grating. The spectral response of each QWIP is selected by selecting the pitch of the diffraction grating. It is possible to further tune the spectral response using the design of the QWIP structure.
The microscanner 10 comprises a mirror and associated piezo-electhc actuators that are operable to drive the lens by selected distances in a series of steps. Each movement of the lens causes a movement of the image relative to the array.
Operation of the apparatus is illustrated in overview in Figure 3. In operation, the microscanner 8 drives the mirror such as to cause movements of the image relative to the array. The microscanner 8 moves the image in a cyclic series of four positions, separated by steps corresponding to the pitch step of the detector array
The four positions of the series are chosen so that each image portion, made up of radiation from a corresponding scene point or region, is held stationary over a detector element of each of the four different types of polarisation sensitivity in turn. As the array and image are moved so that the same image portion is directed to a detector element of each different polarisation sensitivity type, it is ensured that images produced using the detector elements of each different type are in registration with each other.
The image is held stationary at each of the four positions relative to the array during a detection interval, or integration time, between movements. Each detector element of the array detects and integrates received radiation during the integration time. The integration is simultaneous for every detector element of the array, and each detector element produces an electrical signal corresponding to the integrated amount of radiation for that detector element.
The electrical signals of the detector elements are read out by the control processor at the end of the integration time, to produce a field of data, comprising a response signal, or pixel signal, in respect of each detector element.
After an initial movement, the displacement cycle begins with the image portion or pixel 30 being aligned with one of the detector elements 20 and held for the integration and read out time. The image portion is then moved, and held for the integration and read out time, over each of the detector elements 22 24 and 26 in turn, before returning to the detector element 20 to complete a single displacement cycle. The displacement cycle is then be repeated a desired number of times.
The control processor processes the four successive fields of data generated during each displacement cycle in dependence on the polarisation sensitivity and wavelength sensitivity of the detector elements. Registered polarisation- and wavelength-dependent images are obtained by comparison of the fields of data.
By using micro-scanning of an image across the and pattern-of-four detector, the apparatus of the preferred embodiment can be used as a "colour" camera. In the preferred embodiment three colours and two directions of polarisation are provided in each sub-array. The image is moved so that each part is sampled by each of the detector types.
In variants of the preferred embodiment, other microscanner mechanisms are used in place of the piezoelectric actuator and mirror arrangement described above. For instance, a tilting plate or moving lens may be used instead of a tilting mirror. Alternatively, the detector array itself, rather than the radiation forming the image, may be displaced.
It will be understood that further variations of the disclosed arrangements are possible without departing from the invention. For example, whilst the invention is described primarily with reference to a thermal imager, it could equally be applied to other cameras, such as visible light cameras. In addition, alternative arrangements of the detector elements in the array and alternative microscanner displacement patterns may be used in alternative embodiments. The relative positions included in the series of relative positions, and the order of the series, may also be varied.
It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.
Each feature disclosed in the description, and (where appropriate) the drawings may be provided independently or in any appropriate combination.

Claims

1. An infrared detector comprising a plurality of detector elements, the plurality of detector elements comprising a plurality of differently polarisation- sensitive detector elements and a plurality of differently wavelength-sensitive detector elements.
2. An infrared detector according to Claim 1 , wherein the plurality of differently polarisation-sensitive detector elements are sensitive at the SiO2 absorption band.
3. An infrared detector according to Claim 1 or 2, wherein the plurality of differently polarisation sensitive detector elements have a sensitivity that has a maximum as a function of wavelength at a wavelength substantially equal to 9.1 μm or 9.2μm.
4. An infrared detector according to any preceding claim, wherein the plurality of differently wavelength sensitive detector elements have different wavelength sensitivities to the plurality of differently polarisation sensitive detector elements.
5. An infrared detector according to Claim 4, wherein the plurality of differently wavelength sensitive detector elements have different wavelength sensitivities to each other.
6. An infrared detector according to any preceding claim, wherein each of the plurality of differently wavelength sensitive detector elements has a sensitivity that has maximum as a function of wavelength at a wavelength substantially equal to one of 8μm and 10μm.
7. An infrared detector according to any preceding claim, wherein the detector elements are sensitive to three wavelength bands and allow the collection of most of the radiation transmitted in the long wavelength infra-red (LWIR) atmospheric window.
8. An infrared detector according to any preceding claim, wherein the plurality of differently polarisation sensitive detector elements are two differently polarisation sensitive detector elements that have substantially the same wavelength sensitivity, or four differently sensitive polarisation detector elements that have substantially the same wavelength sensitivity.
9. An infrared detector according to any preceding claim, wherein the plurality of differently polarisation sensitive detection elements comprise two differently polarisation sensitive detector elements, one detector element sensitive to a polarisation substantially equal to 0° and one detector element sensitive to a polarisation substantially equal to 90°.
10. An infrared detector according to any preceding claim, wherein the plurality of differently wavelength sensitive detector elements have a polarisation sensitivity substantially equal to 45°.
1 1. An infrared detector according to Claim 9 or 10, wherein the polarisations are defined relative to the ground.
12. An infrared detector according to any preceding claim, wherein the plurality of differently wavelength sensitive detector elements comprises at least one detector element that is distinct from the plurality of differently polarisation sensitive detector elements.
13. An infrared detector according to any preceding claim, wherein the plurality of detector elements are arranged in an array comprising a plurality of non-overlapping sub-arrays, and each sub-array comprises at least two differently polarisation sensitive detector elements and at least two differently polarisation wavelength sensitive detector elements.
14. An infrared detector according to any preceding claim, wherein each detector element comprises a quantum well infra-red photodetector (QWIP).
15. An imaging apparatus for imaging a scene, comprising an infrared detector according to any of Claims 1 to 14, wherein the detector elements are arranged in an array and the apparatus further comprises means for directing radiation from the scene to form an image at the array.
16. An imaging apparatus according to Claim 15, further comprising means for causing relative movement of the image and the array, configured to operate such that the image and the array are placed in a series of relative positions so that the same portion or portions of the image are directed to the detector elements having different polarisation sensitivities and different wavelength sensitivities.
17. An imaging apparatus according to Claim 16, further comprising processing means for processing the response signals from the detector elements to obtain both polarisation-dependent and wavelength-dependent representations of the image of the scene that are in spatial registration with each other
18. A method of imaging a scene, comprising directing radiation from the scene to an infrared detector according to any of Claims 1 to 14, wherein the detector elements of the infrared detector are arranged in an array, the radiation is directed from the scene to form an image at the array of detector elements, and the method further comprises detecting radiation at each of a plurality of different polarisations, detecting radiation at each of a plurality of different wavelengths and generating image data representative of at least one polarisation-dependent image and at least one wavelength-dependent image in dependence on the detected radiation.
PCT/EP2009/057730 2008-06-25 2009-06-22 Imaging apparatus and method WO2009156362A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP09769211A EP2301243A1 (en) 2008-06-25 2009-06-22 Imaging apparatus and method

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0811633.7A GB2462137B (en) 2008-06-25 2008-06-25 Imaging apparatus and method
GB0811633.7 2008-06-25

Publications (1)

Publication Number Publication Date
WO2009156362A1 true WO2009156362A1 (en) 2009-12-30

Family

ID=39683128

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2009/057730 WO2009156362A1 (en) 2008-06-25 2009-06-22 Imaging apparatus and method

Country Status (3)

Country Link
EP (1) EP2301243A1 (en)
GB (1) GB2462137B (en)
WO (1) WO2009156362A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140139684A1 (en) * 2012-05-13 2014-05-22 Elbit Systems Electro-Optics Elop Ltd. Infrared detector with increased image resolution
JP2018040976A (en) * 2016-09-08 2018-03-15 国立大学法人宇都宮大学 Filter, image capturing device, and image capturing system
WO2019164578A3 (en) * 2018-01-03 2019-10-17 Flir Systems Ab Dynamic determination of radiometric values using multiple band sensor array systems and methods
US20220260340A1 (en) * 2021-02-17 2022-08-18 Bae Systems Information And Electronic Systems Integration Inc. Push broom clutter rejection using a multimodal filter

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5479015A (en) * 1994-08-18 1995-12-26 Grumman Aerospace Corporation Multi-image detector assembly
FR2833794A1 (en) * 2001-12-14 2003-06-20 Thales Sa Naval land based air carriage multiple function image detection matrix having different type elementary cells and microsweep system forming wall images and sets global images formed elementary detector types.
US6977774B1 (en) * 1998-08-07 2005-12-20 Autocloning Technology, Ltd. Polarizer
US20060000974A1 (en) * 2004-07-01 2006-01-05 Lockheed Martin Corporation Polarization and wavelength-selective patch-coupled infrared photodetector
WO2007070306A2 (en) * 2005-12-09 2007-06-21 Arete Associates Miniature integrated multisectral/multipolarization digital camera
WO2008085679A1 (en) * 2007-01-11 2008-07-17 Raytheon Company Video camera system using multiple image sensors

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5483066A (en) * 1994-06-08 1996-01-09 Loral Corporation Polarization diverse infrared object recognition system and method
JPH09245209A (en) * 1996-03-13 1997-09-19 Matsushita Electric Works Ltd Infrared ray type human body detector

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5479015A (en) * 1994-08-18 1995-12-26 Grumman Aerospace Corporation Multi-image detector assembly
US6977774B1 (en) * 1998-08-07 2005-12-20 Autocloning Technology, Ltd. Polarizer
FR2833794A1 (en) * 2001-12-14 2003-06-20 Thales Sa Naval land based air carriage multiple function image detection matrix having different type elementary cells and microsweep system forming wall images and sets global images formed elementary detector types.
US20060000974A1 (en) * 2004-07-01 2006-01-05 Lockheed Martin Corporation Polarization and wavelength-selective patch-coupled infrared photodetector
WO2007070306A2 (en) * 2005-12-09 2007-06-21 Arete Associates Miniature integrated multisectral/multipolarization digital camera
WO2008085679A1 (en) * 2007-01-11 2008-07-17 Raytheon Company Video camera system using multiple image sensors

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP2301243A1 *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140139684A1 (en) * 2012-05-13 2014-05-22 Elbit Systems Electro-Optics Elop Ltd. Infrared detector with increased image resolution
US9894292B2 (en) * 2012-05-13 2018-02-13 Elbit Systems Electro-Optics Elop Ltd. Infrared detector with increased image resolution and method for use thereof
US20180160056A1 (en) * 2012-05-13 2018-06-07 Elbit Systems Electro-Optics Elop Ltd. Infrared detector with increased image resolution
US10547799B2 (en) 2012-05-13 2020-01-28 Elbit Systems Electro-Optics Elop Ltd. Infrared detector with increased image resolution
JP2018040976A (en) * 2016-09-08 2018-03-15 国立大学法人宇都宮大学 Filter, image capturing device, and image capturing system
WO2019164578A3 (en) * 2018-01-03 2019-10-17 Flir Systems Ab Dynamic determination of radiometric values using multiple band sensor array systems and methods
US11474030B2 (en) 2018-01-03 2022-10-18 Flir Systems Ab Dynamic determination of radiometric values using multiple band sensor array systems and methods
US20220260340A1 (en) * 2021-02-17 2022-08-18 Bae Systems Information And Electronic Systems Integration Inc. Push broom clutter rejection using a multimodal filter
WO2022177926A1 (en) * 2021-02-17 2022-08-25 Bae Systems Information And Electronic Systems Integration Inc. Push broom clutter rejection using a multimodal filter

Also Published As

Publication number Publication date
GB2462137A (en) 2010-02-03
GB2462137B (en) 2013-01-23
EP2301243A1 (en) 2011-03-30
GB0811633D0 (en) 2008-07-30

Similar Documents

Publication Publication Date Title
JP7426377B2 (en) Multispectral ranging/imaging sensor arrays and systems
US6075235A (en) High-resolution polarization-sensitive imaging sensors
US8687073B2 (en) Multi-channel imaging devices
US5471056A (en) Airborne scanner image spectrometer
US10317205B2 (en) Depth measurement using a phase grating
US7193214B1 (en) Sensor having differential polarization and a network comprised of several such sensors
US7109488B2 (en) Multi-color infrared imaging device
JP6348271B2 (en) Mixed material multispectral Stirling array sensor
US9354045B1 (en) Image based angle sensor
Bodkin et al. Snapshot hyperspectral imaging: the hyperpixel array camera
Bodkin et al. Video-rate chemical identification and visualization with snapshot hyperspectral imaging
WO2007087372A2 (en) Spatial image modulation to improve performance of computed tomography imaging spectrometer
US20160011050A1 (en) Imaging unit
WO2002039726A2 (en) Multicolor staring sensor system
WO2009156362A1 (en) Imaging apparatus and method
Carter et al. Livermore imaging Fourier transform infrared spectrometer (LIFTIRS)
JP2020139952A (en) Method and device for detecting incident laser radiation on spacecraft
CN110471050A (en) The method of structure light imaging system and scanning scene
Dulski et al. Infrared uncooled cameras used in multi-sensor systems for perimeter protection
WO2009101103A1 (en) An imaging apparatus
Chun et al. Polarization-sensitive infrared sensor for target discrimination
Puckrin et al. Airborne infrared-hyperspectral mapping for detection of gaseous and solid targets
Weeks et al. Pseudo-imaging the spectral-temporal evolution of energetic transient events
JP3203684B2 (en) Spectral imaging optical device
Garcia-Diaz et al. Embedded IR multi aperture imaging for surveillance applications

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 09769211

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

WWE Wipo information: entry into national phase

Ref document number: 2009769211

Country of ref document: EP