Image-based determination of CO and CO
View Patent ↗What is disclosed is a system and method for image-based determination of concentration of CO and CO 2 in a vehicle's exhaust gas in an emissions testing environment. In one embodiment, the present method involves receiving an IR image of the exhaust plume of a motor vehicle intended to be tested for CO and CO 2 concentrations. The IR image has been captured using a mid-wave infrared camera with at least one optical filter tuned to the infrared absorption band of CO and CO 2 . The images are pre-processed to isolate pixels which contain the exhaust plume. The intensity values of pixels in those isolated regions are normalized and concentrations of CO and CO 2 are determined via a calibration curve which relates pixel intensities to concentrations. The concentrations are compared to an emissions standard set for the vehicle to determine whether the vehicle is a gross polluter.
1. A method for image-based determination of concentration of CO and CO 2 in a vehicle's exhaust gas, the method comprising:
receiving at least one IR image of an exhaust plume of a motor vehicle, said IR image having been captured using a mid-wave infrared camera having at least one optical filter tuned to the infrared absorption band of any of: CO and CO 2 , said IR image comprising an array of pixels with intensity values obtained at said absorption band, and said IR image comprising at least a region of pixels in said array of pixels representing the exhaust plume and a reference region of pixels in said array of pixels representing a reference surface comprising a known radiance with a known temperature and emissivity;
isolating said region of pixels representing said exhaust plume;
isolating said reference region of pixels representing said reference surface;
normalizing intensity values of pixels in said isolated region by a value of said known radiance of said reference surface; and
determining, based on said normalizing, a concentration of any of CO and CO 2 in said exhaust plume using a calibration curve which relates pixel intensities to concentration levels.
2. The method of claim 1 , wherein said calibration curve is derived using any of: a physics-based parameterized model which relates pixel intensities to gas concentration in any of: parts-per-million units, a volumetric percentage, and grams/mile, and by experimental methods that produce a result that can be represented in terms of a unit of measurement.
3. The method of claim 1 , wherein said mid-wave infrared camera has a sensitivity band that includes 4.0 μm to 4.5 μm to collect light emitted by a roto-vibrational mode of CO 2 molecules, and a spectral band-pass filter which allows CO 2 emission light to enter a lens of said camera.
4. The method of claim 3 , wherein said filter comprises a narrow band-pass filter to increase a contrast of CO 2 relative to a background radiation.
5. The method of claim 1 , wherein said mid-wave infrared camera has a sensitivity band that includes 4.5 μm to 5.0 μm to collect light emitted by a roto-vibrational mode of CO molecules, and a spectral band-pass filter which allows CO emission light to enter a lens of said camera.
6. The method of claim 5 , wherein said filter comprises a narrow band-pass filter to increase a contrast of CO relative to a background radiation.
7. The method of claim 1 , further comprising comparing said determined CO 2 concentration to an emissions standard set for said vehicle to determine whether said vehicle is a gross polluter, said vehicle being a gross polluter if said determined concentration is at least twice the limit set by said emissions standard for this vehicle.
8. The method of claim 7 , further comprising an emissions enforcement authority issuing a citation to a registered owner of said vehicle in response to said vehicle being a gross polluter.
9. The method of claim 1 , further comprising comparing said determined CO concentration to an emissions standard set for said vehicle to determine whether said vehicle is a gross polluter, said vehicle being a gross polluter if said determined concentration is at least twice the limit set by said emissions standard for this vehicle.
10. The method of claim 9 , further comprising an emissions enforcement authority issuing a citation to a registered owner of said vehicle in response to said vehicle being a gross polluter.
11. The method of claim 1 , further comprising communicating said concentration to any of: a memory, a storage device, a graphical display, a telephonic messaging system, and a computer workstation.
12. An emissions detection system for image-based determination of concentration of CO and CO 2 in a vehicle's exhaust gas, the system comprising:
a mid-wave infrared camera system having at least one optical filter tuned to the infrared absorption band of any of: CO and CO 2 ; and
a processor in communication with said camera and a memory, said processor executing machine readable instructions for performing:
receiving at least one IR image of an exhaust plume of a motor vehicle, said IR image having been captured using said mid-wave infrared camera, said IR image comprising, in part, an array of pixels having intensity values obtained at said absorption band, and said IR image comprising at least a region of pixels in said array of pixels representing the exhaust plume and a reference region of pixels in said array of pixels representing a reference surface comprising a known radiance with a known temperature and emissivity;
isolating said region of pixels representing said exhaust plume;
isolating said reference region of pixels representing said reference surface;
normalizing intensity values of pixels in said isolated region by a value of said known radiance of said reference surface; and
determining, based on said normalizing, a concentration of any of CO and CO 2 in said exhaust plume using a calibration curve which relates pixel intensities to concentration levels.
13. The emissions detection system of claim 12 , wherein said calibration curve is derived using any of: a physics-based parameterized model which relates pixel intensities to gas concentration in any of: parts-per-million units, a volumetric percentage, and grams/mile, and by experimental methods that produce a result that can be represented in terms of a unit of measurement.
14. The emissions detection system of claim 12 , wherein said mid-wave infrared camera has a sensitivity band that includes 4.0 μm to 4.5 μm to collect light emitted by a roto-vibrational mode of CO 2 molecules, and a spectral band-pass filter which allows CO 2 emission light to enter a lens of said camera.
15. The emissions detection system of claim 14 , wherein said filter comprises a narrow band-pass filter to increase a contrast of CO 2 relative to a background radiation.
16. The emissions detection system of claim 12 , wherein said mid-wave infrared camera has a sensitivity band that includes 4.5 μm to 5.0 μm to collect light emitted by a roto-vibrational mode of CO molecules, and a spectral band-pass filter which allows CO emission light to enter a lens of said camera.
17. The emissions detection system of claim 16 , wherein said filter comprises a narrow band-pass filter to increase a contrast of CO relative to a background radiation.
18. The emissions detection system of claim 12 , further comprising comparing said determined CO 2 concentration to an emissions standard set for said vehicle to determine whether said vehicle is a gross polluter, said vehicle being a gross polluter if said determined concentration is at least twice the limit set by said emissions standard for this vehicle.
19. The emissions detection system of claim 18 , further comprising an emissions enforcement authority issuing a citation to a registered owner of said vehicle in response to said vehicle being a gross polluter.
20. The emissions detection system of claim 12 , further comprising comparing said determined CO concentration to an emissions standard set for said vehicle to determine whether said vehicle is a gross polluter, said vehicle being a gross polluter if said determined concentration is at least twice the limit set by said emissions standard for this vehicle.
21. The emissions detection system of claim 20 , further comprising an emissions enforcement authority issuing a citation to a registered owner of said vehicle in response to said vehicle being a gross polluter.
22. The emissions detection system of claim 12 , further comprising communicating said concentration to any of: said memory, a storage device, a graphical display, a telephonic messaging system, and a computer workstation.
23. A computer implemented method for image-based determination of concentration of CO and CO 2 in a vehicle's exhaust gas, the method comprising:
receiving at least one IR image of an exhaust plume of a motor vehicle intended to be tested for exhaust emissions, said IR image having been captured using a mid-wave infrared camera having at least one optical filter tuned to the infrared absorption band of at least one of: CO and CO 2 said IR image comprising an array of pixels with intensity values obtained at said absorption band;
isolating a region of pixels in the array of pixels representing said exhaust plume;
isolating a reference region of pixels in the array of pixels representing a reference surface;
normalizing intensity values of pixels in said isolated region by a value of a known radiance of said reference surface with a known temperature and emissivity;
determining, based on said normalizing, a concentration of any of CO and CO 2 in said exhaust plume using a calibration curve which relates pixel intensities to concentration levels; and
comparing said determined concentrations to an emissions standard set for said vehicle to determine whether said vehicle is a gross polluter, said vehicle being a gross polluter if said determined concentration is at least twice the limit set by said emissions standard for this vehicle.