Image-based determination of CO and CO;concentrations in vehicle exhaust gas emissions

• US 8,854,223 B2
• Filed: 03/14/2012
• Issued: 10/07/2014
• Est. Priority Date: 01/18/2012
• Status: Active Grant

• Current Assignee: Conduent Business Services, LLC (Conduent, Inc.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Cardoso, George Cunha, Mestha, Lalit Keshav
• Primary Examiner(s): HUNNINGS, TRAVIS R
• Application Number:
  US13/419,856
• Publication Number:
  US 20130181836A1
• Time in Patent Office: 937 Days
• Field of Search: 340/463, 340/540, 340/603, 340/632, 340/627, 340/628, 340/633, 340/630
• US Class Current: 340/628
• CPC Class Codes: G01M 15/108 using optical methods

Abstract

What is disclosed is a system and method for image-based determination of concentration of CO and CO₂ 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 CO₂ 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 CO₂. 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 CO₂ 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.

Claims

1. A method for image-based determination of concentration of CO and CO₂ 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 CO₂, 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 CO₂ 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 μ

m to 4.5 μ

m to collect light emitted by a roto-vibrational mode of CO₂ molecules, and a spectral band-pass filter which allows CO₂ 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 CO₂ 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 μ

m to 5.0 μ

m 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 CO₂ 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 CO₂ 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 CO₂; 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 CO₂ 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 μ

m to 4.5 μ

m to collect light emitted by a roto-vibrational mode of CO₂ molecules, and a spectral band-pass filter which allows CO₂ 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 CO₂ 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 μ

m to 5.0 μ

m 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 CO₂ 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 CO₂ 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 CO₂ 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 CO₂ 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.