Quantitative imaging of gas emissions utilizing optical techniques
First Claim
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 A0 and 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; and
finally, the resulting gas concentration image is superimposed on a visible image C of the scene and the result is displayed.
2 Assignments
0 Petitions
Accused Products
Abstract
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.
72 Citations
25 Claims
-
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 A0 and 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; and
finally, the resulting gas concentration image is superimposed on a visible image C of the scene and the result is displayed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- the use of gas correlation techniques for spectral identification of substances and cancellation of spatially varying background temperatures and emissivities;
-
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 A0 and B0 including 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; and
means for displaying the result by superimposing the resulting gas concentration image on a visible image C of the scene. - View Dependent Claims (11, 12, 13, 14, 15, 16)
-
-
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. - View Dependent Claims (18, 19, 20)
-
-
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. - View Dependent Claims (22, 23, 24, 25)
-
Specification