IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0169300
(2002-06-27)
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우선권정보 |
SE-9904836 (1999-12-28) |
국제출원번호 |
PCT/SE00/02686
(2000-12-28)
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국제공개번호 |
WO01/48459
(2001-07-05)
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발명자
/ 주소 |
- Edner, Hans
- Sandsten, Jonas
- Svanberg, Sune
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출원인 / 주소 |
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대리인 / 주소 |
Boyle, Fredrickson, Newholm, Stein & Gratz, S.C.
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인용정보 |
피인용 횟수 :
41 인용 특허 :
7 |
초록
▼
A method for quantitative imaging of gas emissions utilizing optical techniques combining gas correlation techniques with thermal background radiation or gas self-emission radiation is presented. A simultaneous recording of images with and without filtering through a gas-filled cell is utilized for
A method for quantitative imaging of gas emissions utilizing optical techniques combining gas correlation techniques with thermal background radiation or gas self-emission radiation is presented. A simultaneous recording of images with and without filtering through a gas-filled cell is utilized for the identification of a selected gas. A new calibration method provides the display of the integrated gas concentration spatially resolved in the generated final image. The procedure includes methods for a correct subtraction of the zero level, consisting of self-radiation from the dual-image camera device including the as correlation cell and electronic offset, and for the calculation of the specific absorption as a function of the difference temperature between the background and the gas emission.
대표청구항
▼
1. A method for imaging of gas distributions utilizing optical techniques, comprising: the use of gas correlation techniques for spectral identification of substances and cancellation of spatially varying background temperatures and emissivities; the utilization of absorption of natural thermal back
1. A method for imaging of gas distributions utilizing optical techniques, comprising: the use of gas correlation techniques for spectral identification of substances and cancellation of spatially varying background temperatures and emissivities; the utilization of absorption of natural thermal background radiation or self-emission spectrum due to a selected gas (passive recording technique); and wherein two images, A and B are stored using a dual-image infrared camera device adapted to a selected wavelength region where the gas absorption or emission spectrum is present; A—is the infrared scene recorded in one of the images (direct image); B—is the same scene recorded with the infrared light passing a gas correlation cell; characterized by a calibration procedure as follows: the background temperature is recorded using the information contained in image A;the relevant zero images A0and B0, consisting of self-radiation from the dual-image camera device including the gas correlation cell and electronic offset, are subtracted from A and B, respectively, wherein the individual zero level in each pixel of the images has been determined before the gas measurement by recording a black body radiator at different temperatures and plotting the pixel intensity obtained versus a theoretically calculated intensity, and the axis intercept of a straight line, which is fitted to the data, provides the zero level;the images are digitally overlapped within a field of interest containing the gas release, and the continuing image processing is constrained to this field;a gas correlation image, G=(A−A0)/(B−Bo), is calculated;the concentration level in each pixel of image G is calculated using a diagram showing the integrated transmission within the chosen spectral profile as a function of the integrated concentration of the gas expressed in ppm×meter for the particular gas, temperature difference between the background temperature and the gas emission temperature, and absolute temperatures; andfinally, the resulting gas concentration image is superimposed on a visible image C of the scene and the result is displayed. 2. A method as claimed in claim 1, characterized in that the resulting gas concentration image is colour-coded. 3. A method as claimed in claim 1 or 2, characterized by the adaption of the infrared camera detector integration time, spatial/temporal filtering, and concentration threshold to the measured gas concentration level and dynamics at a rate allowing concentration calibrated images to be shown as movies. 4. A method as claimed in claim 1 or 2, characterized by a determination of the gas flux by combining the gas, concentration image with the gas flow velocity, calculated through correlation of the displacement of the gas cloud in temporally separated images. 5. A method as claimed in claim 1 or 2, characterized of the utilization of a reflector double telescope with off-axis parabolas for simultaneous capturing of the images A and B. The visible image C is simultaneously captured with a camera mounted in close proximity to the telescope. 6. A method as claimed in claim 5, characterized by the use of plane and angled secondary telescope mirrors designed to avoid the self-radiation of the camera to be reflected back into the camera detector. 7. A method as claimed in claim 1 or 2, characterized by the use of two infrared cameras mounted together for simultaneous capturing of the images A and B. The visible image C is simultaneously captured with a camera mounted in close proximity to the infrared cameras. 8. A method as claimed in claim 1 or 2, characterized by the use of an infrared camera with two detectors capturing images A and B with the aid of a beam-splitter and gas correlation cell inside the camera. The visible image C is simultaneously captured with a camera mounted in close proximity to the infrared camera. 9. A method as claimed in claim 1 or 2, characterized by the use of an infrared ca mera with one detector sequentially capturing images A and B by the use of a chopper switching the gas correlation cell in and out in front of the detector. The visible image C is simultaneously captured with a camera mounted in close proximity to the infrared camera. 10. A device for imaging of gas distributions utilizing optical techniques, comprising: a dual-image infrared camera device, for storing two images, A and B and adapted to a selected wavelength region where the gas absorption or emission spectrum is present wherein: A—is the infrared scene recorded in one of the images (direct image);B—is the same scene recorded with the infrared light passing a gas correlation cell;characterized in that the camera device includes means for calibration comprising:means for recording the background temperature using the information contained in image A;means for determining and storing the relevant zero images A0and B0including means for recording a black body radiator at different temperatures and plotting the pixel intensity obtained versus a theoretically calculated intensity, and the axis intercept of a straight line, which is fitted to the data, for providing the individual zero level in each pixel of the images, consisting of self-radiation from the dual-image camera device;means for calculating a gas correlation image, G=(A−A0)/(B−B0);means for calculating the concentration level in each pixel of image G arranged to use a diagram showing the integrated transmission within the chosen spectral profile as a function of the integrated concentration of the gas expressed in ppm× meter for the particular gas, temperature difference between the background temperature and the gas emission temperature, and absolute temperatures; andmeans for displaying the result by superimposing the resulting gas concentration image on a visible image C of the scene. 11. A device according to claim 10, characterised in that the display means is arranged to colour-code the gas concentration image. 12. A device according to claim 10 or 11, consisting of a reflector double telescope with two off-axis parabolas for simultaneous capturing of the images A and B, two plane and angled secondary mirrors designed to avoid the self-radiation of the infrared camera to be reflected back into the camera detector, and a camera, which is used to simultaneously capture the visible image C, mounted in close proximity to the telescope. 13. A device according to claim 10 or 11, consisting of two infrared micro-bolometer cameras mounted together for simultaneous capturing of the images A and B. The sensitivities of the infrared cameras are tuned to the selected wavelength region with the use of antireflection coatings and interference filters, and a camera, which is used to simultaneously capture the visible image C, mounted in close proximity to the infrared cameras. 14. A device according to claim 10 or 11, consisting of two infrared QWIP (Quantum Well Infrared Photodetector) cameras mounted together for simultaneous capturing of the images A and B with sensitivities of the detectors optimized for the selected wavelength region, and a camera, which is used to simultaneously capture the visible image C, mounted in close proximity to the infrared cameras. 15. A device according to claim 10 or 11, consisting of an infrared camera with two detectors capturing images A and B with the aid of a beam-splitter and gas correlation cell inside the camera, and a camera, which is used to simultaneously capture the visible image C, mounted in close proximity to the infrared camera. 16. A device according to claim 10 or 11, consisting of an infrared camera with one detector sequentially capturing images A and B by the use of a chopper switching the gas correlation cell in and out in front of the detector, and a camera, which is used to simultaneously capture the visible image C, mounted in close proximity to the infrared camera. 17. A gas correlation imaging device comprising: at least one image detector oriented so as to record a plurality of infrared images of a gaseous region; a gas correlation cell disposed relative to the at least one of the image detectors such that one of the plurality of images of the gaseous region passes through the gas correlation cell before being recorded by the at least one of the image detectors; and a computer linked to the at least one of the image detectors for processing each received image of the gaseous region with the computer configured to subtract an image offset from each one of the plurality of images that is based on a recorded background temperature. 18. A gas correlation imaging device according to claim 17 comprising a plurality of the image detectors with one of the image detectors spaced from the other one of the image detectors, and wherein (a) the gas correlation cell is disposed relative to one of the plurality of the image detectors such that one of the plurality of infrared images passes through the gas correlation cell before reaching the one of the plurality of image detectors, (b) a first infrared image of the plurality of infrared images comprised of a plurality pixels is received by one of the plurality of the image detectors without passing through the gas correlation cell and a second infrared image of the plurality of infrared images comprised of a plurality of pixels is received by the other one of the plurality of the image detectors after passing through the gas correlation cell, (c) the image offset is based on recording a black body radiator at different temperatures, and (d) the image offset is applied by the computer to each pixel of each one of the images. 19. A gas correlation imaging device according to claim 18 wherein the plurality of image detectors comprise a dual infrared camera device and further comprising a double telescope optical lens arrangement for directing one of the images onto one of the image detectors of the dual infrared camera device and the other one of the images onto the other one of the image detectors with the gas correlation cell disposed between the gaseous region and the other one of the image detectors of the dual infrared camera device. 20. A gas correlation imaging device according to claim 17 further comprising a visible image camera recording a visible image of the gaseous region and a linked to the computer that superimposes in real time on the visible image display color coded gas concentration image formed from the plurality of infrared images. 21. A method of imaging gaseous emissions comprising: (a) providing at least one image detector oriented so as to record a plurality of infrared images of a gaseous region, a gas correlation cell disposed relative to the at least one of the image detectors such that at least one of the plurality of images of the gaseous region passes through the gas correlation cell before being recorded by the at least one of the image detectors, and a computer linked to the at least one image detector for processing the plurality of recorded infrared images; (b) recording a first infrared image of the gaseous region without the image passing through the gas correlation cell before being recorded; (c) recording a second infrared image of the gaseous region after the image has passed through the gas correlation cell; (d) obtaining a temperature of a background; (e) using the temperature of the background to obtain an image offset; (f) determining a gas correlation image comprised of a plurality of pixels using the first infrared image, the second infrared image, and the offset; and (g) determining a gas concentration level for each pixel of the gas correlation image. 22. A method of imaging gaseous emissions according to claim 21 wherein before step (e) obtaining the image offset comprises obtaining a transmittance value using a temperature of the gaseous region to calculate a difference between the temperature of the background region and the temperature of the gaseous region, and thereafter using the calculated temperature difference to obtain a relative transmittance value from a function of relative transmittance versus temperature difference produced by recording a black body radiator at a plurality of temperatures, and wherein the obtained transmittance value is subtracted from the value of each pixel of the first and second infrared images. 23. A method of imaging gaseous emissions according to claim 21 wherein in step (e) the gas correlation image is the result of (1) subtracting the image offset from the first infrared image to produce a first result, (2) subtracting the image offset from the second infrared image to produce a second result, and thereafter (3) dividing the first result by the second result. 24. A method of imaging gaseous emissions according to claim 21 wherein before step (e) the step further comprising digitally overlapping the first infrared image and the second infrared image, and thereafter determining the gas correlation image and the gas concentration level only for an image field that defines gas in the gaseous region. 25. A method of imaging gaseous emissions according to claim 21 further comprising providing a visible image camera that simultaneously records a visible light image of the gaseous region during steps (b) and (c), and after step (g) the step further comprising assigning a color to each pixel of the gas correlation image based on the gas concentration level determined for that pixel in step (g) to create a colorized gas correlation image and thereafter displaying the colorized gas correlation image superimposed on the visible light image of the gaseous region in real time.
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