Window obscuration sensors for mobile gas and chemical imaging cameras
An infrared (IR) imaging system for determining a concentration of a target species in an object is disclosed. The imaging system can include an optical system including a focal plane array (FPA) unit behind an optical window. The optical system can have components defining at least two optical channels thereof, said at least two optical channels being spatially and spectrally different from one another. Each of the at least two optical channels can be positioned to transfer IR radiation incident on the optical system towards the optical FPA. The system can include a processing unit containing a processor that can be configured to acquire multispectral optical data representing said target species from the IR radiation received at the optical FPA. One or more of the optical channels may be used in detecting objects on or near the optical window, to avoid false detections of said target species.
1. An infrared (IR) imaging system comprising:
a housing;
an optical window disposed on the housing;
an optical detector system disposed within the housing; and
a plurality of spatially and spectrally distinct optical channels that transfer incident IR radiation from the optical window to the optical detector system, wherein a first optical channel out of the plurality of optical channels has a focus distance that is closer to the optical window than at least some of the other optical channels of the plurality of optical channels to detect obscuration that may degrade operation of the system.
2. The IR imaging system of claim 1 , wherein the first optical channel out of the plurality of optical channels has a focus less than 2 meters and other optical channels of the plurality of optical channels have a focus of greater than 10 meters.
3. The IR imaging system of claim 1 , wherein at least some of the other optical channels of the plurality of optical channels have focus distances at least 5 meters greater than the focus distance of the first optical channel.
4. The IR imaging system of claim 1 , wherein the first optical channel is in focus at the optical window to detect obscuration that may degrade operation of the system.
5. The IR imaging system of claim 1 , further comprising:
a processing unit comprising processing electronics configured to process image data from the first optical channel to detect obscuration that may degrade operation of the system.
6. The IR imaging system of claim 5 , wherein:
a second optical channel out of the plurality of optical channels is in focus at the optical window; and
the processing unit is configured to compare image data from the first and second optical channels to detect obscuration that may degrade operation of the system.
7. The IR imaging system of claim 1 , wherein the window is embedded in the housing or is in an opening in the housing.
8. An infrared (IR) imaging system for imaging a target species in a scene, the IR imaging system comprising:
an optical window;
a first camera system configured to acquire infrared image data of the scene through the optical window;
a second camera system focused closer to the optical window than the first camera system; and
a processing unit containing a processor configured to:
analyze the infrared image data from the first camera system to detect the target species based on the infrared image data; and
analyze image data from the second camera system to determine whether obscuration is present that may degrade operation of the system based on the image data from the second camera system.
9. The IR imaging system of claim 8 , wherein said processing unit is configured to provide a window obscuration alert after determining that obscuration is present that may degrade operation of the system.
10. The IR imaging system of claim 8 , wherein said processing unit is configured to compensate for effects of attenuation due to obscuration when analyzing the infrared image data to detect the target species.
11. The IR imaging system of claim 8 , wherein the processing unit containing the processor is configured to determine whether obscuration is present that may degrade operation of the system based on the image data from the second camera system by:
receiving a first image from a first portion of the second camera system;
receiving a second image from a second portion of the second camera system;
transforming the first and second images into respective first and second gradient images;
determining that the first and second gradient images have a cross-correlation value that exceeds a first predetermined threshold; and
providing a window obscuration alert after determining that the cross-correlation value exceeds the first predetermined threshold.
12. A method of detecting obscuration of an optical window in an IR imaging system, the IR imaging system comprising processing circuitry and a plurality of spatially and spectrally distinct optical channels, each optical channel including a set of lenses that focus incident IR light on a respective portion of an optical detector system, the method comprising:
with the processing circuitry, receiving a first image from a first optical channel in the plurality of optical channels;
with the processing circuitry, receiving a second image from a second optical channel in the plurality of optical channels; and
with the processing circuitry, analyzing the first and second images to detect obscuration that may degrade operation of the system, said analyzing comprising:
creating first and second gradient images from the first and second images, respectively;
cross-correlating the first and second gradient images; and
determining that at least one cross-correlation between the first and second gradient images exceeds a first window obscuration threshold and that the first and second gradient images exceed a second window obscuration threshold and, in response, providing an alert that the optical window is obscured.
13. The method of claim 12 , wherein analyzing the first and second images comprises, with the processing circuitry, comparing the first and second images to identify obscuration that may degrade operation of the system.
14. The method of claim 12 , wherein analyzing the first and second images comprises, with the processing circuitry, comparing the first and second images and using differences between the first and second images caused by parallax to determine whether obscuration is present that may degrade operation of the system.
15. The method of claim 12 , wherein analyzing the first and second images comprises evaluating how much of the images are in focus to detect obscuration that may degrade operation of the system.
16. The method of claim 12 , wherein analyzing the first and second images comprises evaluating contrast levels of the images to detect obscuration that may degrade operation of the system.
17. The method of claim 12 , further comprising adjusting image data from the plurality of optical channels to compensate for effects of attenuation due to obscuration.
18. The method of claim 12 , wherein analyzing the first and second images comprises evaluating whether image data exceeds a threshold to determine whether obscuration is present that may degrade operation of the system.
19. The method of claim 12 , further comprising detecting a target species based on image data from said plurality of spatially and spectrally distinct optical channels.