Calibration and quantification method for gas imaging camera
The calibration/verification system and method for gas imaging infrared cameras standardizes the procedures to objectively and consistently check performance of gas imaging infrared cameras. This system includes a background board maintaining a uniform temperature, a target cell filled with a target compound and disposed in front of the background board, a reference cell filled with a reference compound and disposed in front of the background board, and an analyzer coupled to the camera that captures images of the gas cell and the reference cell. The analyzer compares the intensity difference and the temperature difference of rays passing through the target cell and reference cell to a reference relationship data of a quality control chart to determine whether the camera is in a working condition. The method is further extended to provide a quantitative measurement of a hydrocarbon plume from a gas imaging infrared camera.
1. A leak quantification system, comprising:
an analyzer coupled to a gas imaging camera that captures images of a scene which include a hydrocarbon plume of unknown concentration, the analyzer including a machine readable storage medium that provides instructions that cause a machine apparatus to perform operations to quantify a product of a concentration and a depth of the hydrocarbon plume and a mass leak rate, the operations comprising:
detecting each pixel that is included within boundaries of the hydrocarbon plume;
detecting an average intensity of attenuated rays passing through the hydrocarbon plume for said each pixel within the boundaries of the hydrocarbon plume;
detecting an average intensity of unattenuated rays, which are not attenuated by the hydrocarbon plume, for said each pixel within the boundaries of the hydrocarbon plume;
detecting a temperature of a background for said each pixel within the boundaries of the hydrocarbon plume;
acquiring a temperature of the hydrocarbon plume for said each pixel within the boundaries of the hydrocarbon plume;
calculating an intensity difference between the average intensity of the attenuated rays and the average intensity of the unattenuated rays for said each pixel within the boundaries of the hydrocarbon plume;
calculating a temperature difference between the hydrocarbon plume and the background for said each pixel within the boundaries of the hydrocarbon plume;
using a pre-established intensity difference and temperature difference chart to determine the product of the concentration and the depth of the hydrocarbon plume;
determining a size of the hydrocarbon plume using an optical magnification, a size of pixels within boundaries of the hydrocarbon plume, and a distance between the gas imaging camera and the hydrocarbon plume to directly measure two dimensions and to estimate the depth of the hydrocarbon plume;
determining a speed and a direction of the hydrocarbon plume by identifying one or more unique features of the hydrocarbon plume and associating those features with previous frames recorded by the gas imaging camera;
establishing a virtual plane perpendicular to the direction of a movement of the hydrocarbon plume to measure flux;
estimating an emissivity of the background using direct measurement or industry standard values;
estimating an absorption coefficient of a hydrocarbon molecule using industry standard values; and
determining the mass leak rate from the product of the concentration and the depth of the hydrocarbon plume, the size of the hydrocarbon plume, and the speed of the hydrocarbon plume.
2. The leak quantification system of the claim 1 , comprised of the acquiring the temperature of the hydrocarbon plume including estimating the temperature of the hydrocarbon plume being the same as an ambient air temperature.
3. The leak quantification system of the claim 1 , comprised of the determining the leak rate comprising:
selecting a specific virtual plane perpendicular to the direction of the movement of the hydrocarbon plume; and
calculating, from the speed of the hydrocarbon plume, a quantity of hydrocarbon which crosses the virtual plane in a given time period to determine the leak rate.
4. The leak quantification system of the claim 1 , comprised of the determining the product of the concentration and the depth by using the pre-established intensity difference and temperature difference chart being including using a formula
I =[ε(λ) B ( T b ,λ)− B ( T g ,λ)]exp [−α(λ)CL] +B ( T g ,λ)
where I represents an intensity detected by the gas imaging camera, εrepresents the emissivity of the background as a function of a wavelength λ, B (T b , λ) represents a Planck function for the background, B(T g , λ) represents a Planck function for the hydrocarbon plume, α(λ) represents the absorption coefficient of the hydrocarbon molecule, C represents the concentration of the hydrocarbon plume, and L represents the depth of the hydrocarbon plume from the perspective of the gas imaging camera.
5. The leak quantification system of the claim 1 , comprised of the gas imaging camera being an infrared camera calibrated to provide thermography measurements.
6. The leak quantification system of the claim 5 , comprised of the detecting the temperature of the background including directly measuring the temperature of the background by the infrared camera calibrated to provide thermography measurements.
7. A leak quantification system, comprising:
a gas imaging camera that captures images of a gas including hydrocarbon plume; and
an analyzer integrated or coupled to the gas imaging camera, the analyzer including a machine readable storage medium that provides instructions that cause a machine apparatus to perform operations to quantify a mass leak rate, the operations comprising:
detecting each pixel that is included within boundaries of the hydrocarbon plume;
detecting an intensity of attenuated rays passing through the hydrocarbon plume for said each pixel within the boundaries of the hydrocarbon plume;
detecting an intensity of unattenuated rays, which are not attenuated by the hydrocarbon plume, for said each pixel within the boundaries of the hydrocarbon plume;
detecting a temperature of a background for said each pixel within the boundaries of the hydrocarbon plume;
acquiring a temperature of the hydrocarbon plume for said each pixel within the boundaries of the hydrocarbon plume;
calculating an intensity difference between the intensity of the attenuated rays and the intensity of the unattenuated rays for said each pixel within the boundaries of the hydrocarbon plume;
calculating a temperature difference between the hydrocarbon plume and the background for said each pixel within the boundaries of the hydrocarbon plume;
estimating an emissivity of the background;
estimating an absorption coefficient of a hydrocarbon molecule;
obtaining a product of a concentration and a depth of the hydrocarbon plume from the intensity difference, the temperature difference, the emissivity of the background and the absorption coefficient of the hydrocarbon plume;
determining a two dimensional size of the hydrocarbon plume by using an optical magnification, a size of pixels within the boundaries of the hydrocarbon plume, and a distance between the gas imaging camera and the hydrocarbon plume;
determining a speed and a direction of a movement of the hydrocarbon plume by using multiple image frames of the hydrocarbon plume recorded by the gas imaging camera;
establishing a virtual plane perpendicular to the direction of the movement of the hydrocarbon plume to measure flux; and
determining the mass leak rate from the product of the concentration and the depth of the hydrocarbon plume, and the speed of the movement of the hydrocarbon plume crossing the virtual plane.
8. The leak quantification system of the claim 7 , comprised of the obtaining the product of the concentration and the depth of the hydrocarbon plume including using a formula:
I =[ε(λ) B ( T b ,λ)− B ( T g ,λ)]exp [−α(λ)CL] + B ( T g ,λ)
where I represents an intensity detected by the gas imaging camera, εrepresents the emissivity of the background as a function of a wavelength λ, B (T b , λ) represents a Planck function for the background, B(T g ,λ) represents a Planck function for the hydrocarbon plume, α(λ) represents the absorption coefficient of the hydrocarbon molecule, C represents the concentration of the hydrocarbon plume, and L represents the depth of the hydrocarbon plume from the perspective of the gas imaging camera.
9. The leak quantification system of the claim 7 , comprised of the acquiring the temperature of the hydrocarbon plume including estimating the temperature of the hydrocarbon plume being the same as ambient air temperature.
10. The leak quantification system of the claim 7 , comprised of the detecting the temperature of the background including directly measuring the temperature of the background by an infrared camera calibrated to provide thermography measurements.
11. The leak quantification system of the claim 7 , comprised of the detecting the intensity of unattenuated rays comprising detecting the intensity of unattenuated rays from a second image with spectral filtering that does not produce a response from the hydrocarbon plume, the leak quantification system further comprising another imaging camera integrated or coupled to the analyzer, the second image being captured by said another imaging camera.
12. The leak quantification system of the claim 7 , comprised of the gas imaging camera detecting the intensity of unattenuated rays.
13. The leak quantification system of the claim 7 , comprised of the determining the mass leak rate comprising:
selecting a virtual plane perpendicular to the direction of the movement of the hydrocarbon plume; and
calculating, from the speed of the hydrocarbon plume, a quantity of hydrocarbon which passes through the virtual plane in a given time period to determine the mass leak rate.
14. A leak quantification system, comprising:
a gas imaging camera that captures images of a gas including hydrocarbon plume; and
an analyzer integrated or coupled to the gas imaging camera, the analyzer including a machine readable storage medium that provides instructions that cause a machine apparatus to perform operations to quantify a product of the concentration and the depth of hydrocarbon plume, the operations comprising:
detecting each pixel that is included within boundaries of the hydrocarbon plume;
detecting an intensity of attenuated rays passing through the hydrocarbon plume for said each pixel within the boundaries of the hydrocarbon plume;
detecting an intensity of unattenuated rays, which are not attenuated by the hydrocarbon plume, for said each pixel within the boundaries of the hydrocarbon plume;
detecting a temperature of a background for said each pixel within the boundaries of the hydrocarbon plume;
acquiring a temperature of the hydrocarbon plume for said each pixel within the boundaries of the hydrocarbon plume;
calculating an intensity difference between the intensity of the attenuated rays and the intensity of the unattenuated rays for said each pixel within the boundaries of the hydrocarbon plume;
calculating a temperature difference between the hydrocarbon plume and the background for said each pixel within the boundaries of the hydrocarbon plume;
estimating an emissivity of the background;
estimating an absorption coefficient of a hydrocarbon molecule; and
obtaining a product of the concentration and the depth of the hydrocarbon plume from the intensity difference, the temperature difference, the emissivity of the background and the absorption coefficient of the hydrocarbon plume.
15. The leak quantification system of the claim 14 , comprised of the obtaining the product of the concentration and the depth of the hydrocarbon plume including using a formula:
I =[ε(λ) B ( T b ,λ)− B ( T g ,λ)]exp [−α(λ)CL] + B ( T g ,λ)
where I represents an intensity detected by the gas imaging camera, εrepresents the emissivity of the background as a function of a wavelength λ, B (T b , λ) represents a Planck function for the background, B (T g , λ) represents a Planck function for the hydrocarbon plume, α(λ) represents the absorption coefficient of the hydrocarbon plume, C represents the concentration of the hydrocarbon plume, and L represents the depth of the hydrocarbon plume from the perspective of the gas imaging camera.
16. The leak quantification system of the claim 14 , comprised of the acquiring the temperature of the hydrocarbon plume including estimating the temperature of the hydrocarbon plume being the same as ambient air temperature.
17. The leak quantification system of the claim 14 , comprised of the detecting the temperature of the background including directly measuring the temperature of the background by an infrared camera calibrated to provide thermography measurements.
18. The leak quantification system of the claim 14 , comprised of the detecting the intensity of unattenuated rays comprising detecting the intensity of unattenuated rays from a second image with spectral filtering that does not produce a response from the hydrocarbon plume, the leak quantification system further comprising another imaging camera integrated or coupled to the analyzer, the second image being captured by said another imaging camera.
19. The leak quantification system of the claim 14 , comprised of the gas imaging camera detecting the intensity of unattenuated rays.