Window obscuration sensors for mobile gas and chemical imaging cameras

• US 10,845,302 B2
• Filed: 10/25/2019
• Issued: 11/24/2020
• Est. Priority Date: 11/09/2017
• Status: Active Grant

• Current Assignee: Rebellion Photonics, Inc. (Honeywell International Inc.)
• Original Assignee: Rebellion Photonics, Inc. (Honeywell International Inc.)
• Inventors: Mallery, Ryan, Balila, Ohad Israel, Kester, Robert Timothy
• Primary Examiner(s): Porta, David P
• Assistant Examiner(s): Boosalis, Fani
• Application Number:
  US16/664,615
• Publication Number:
  US 20200132596A1
• Time in Patent Office: 396 Days
• CPC Class Codes: G01J 2003/2806 Array and filter array
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/0213 using attenuators
• CPC Class Codes: G01J 3/0256 Compact construction
• CPC Class Codes: G01J 3/0264 Electrical interface; User interface
• CPC Class Codes: G01J 3/027 Control of working procedures of a spectrometer; Failure detection; Bandwidth calculation
• CPC Class Codes: G01J 3/0291 Housings; Spectrometer accessories; Spatial arrangement of elements, e.g. folded path arrangements
• CPC Class Codes: G01J 3/0294 Multi-channel spectroscopy
• CPC Class Codes: G01J 3/0297 Constructional arrangements for removing other types of optical noise or for performing calibration
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 5/0014 for sensing the radiation from gases, flames
• CPC Class Codes: G01J 5/0806 Focusing or collimating elements, e.g. lenses or concave mirrors
• CPC Class Codes: G01N 2021/157 Monitoring by optical means
• CPC Class Codes: G01N 2021/1795 Atmospheric mapping of gases
• CPC Class Codes: G01N 2021/3531 without instrumental source, i.e. radiometric
• CPC Class Codes: G01N 21/15 Preventing contamination of the components of the optical system or obstruction of the light path
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 2201/0221 Portable; cableless; compact; hand-held
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

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.

Claims

1. 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, analyzing a first image and a second image, received from respective first and second optical channels of the plurality of spatially and spectrally distinct optical channels, to detect obscuration that may degrade operation of the IR imaging system;

with the processing circuitry, creating first and second gradient images from the first and second images, respectively;

with the processing circuitry, cross-correlating the first and second gradient images; and

with the processing circuitry, 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.

2. The method of claim 1, 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 IR imaging system.

3. The method of claim 1, 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 IR imaging system.

4. The method of claim 1, wherein analyzing the first and second images comprises evaluating how much of the first and second images are in focus to detect obscuration that may degrade operation of the IR imaging system.

5. The method of claim 1, wherein analyzing the first and second images comprises evaluating contrast levels of the first and second images to detect obscuration that may degrade operation of the IR imaging system.

6. The method of claim 1, further comprising adjusting image data from the plurality of spatially and spectrally distinct optical channels to compensate for effects of attenuation due to obscuration.

7. The method of claim 1, 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 IR imaging system.

8. The method of claim 1, further comprising detecting a target species based on image data from said plurality of spatially and spectrally distinct optical channels.

9. The method of claim 1, wherein analyzing the first and second images comprises performing a correlation of the first and second images.

10. An infrared (IR) imaging system comprising:

a housing;

an optical window disposed on the housing;

an optical detector system disposed within the housing;

a plurality of spatially and spectrally distinct optical channels that transfer incident IR radiation from the optical window to the optical detector system, wherein said IR imaging system is configured to detect whether the optical window is obscured; and

processing circuitry configured to;

analyze a first image and a second image, received from respective first and second optical channels of the plurality of spatially and spectrally distinct optical channels, to detect obscuration that may degrade operation of the IR imaging system,

create first and second gradient images from the first and second images, respectively,

cross-correlate the first and second gradient images, and

determine 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.

11. The IR imaging system of claim 10, wherein the processing circuitry is configured to evaluate how much of the first and second images are in focus to detect whether the optical window is obscured.

12. The IR imaging system of claim 10, wherein the processing circuitry is configured to evaluate contrast levels of the first and second to detect whether the optical window is obscured.

13. The IR imaging system of claim 10, wherein the processing circuitry is configured to perform edge enhancement of the first and second.

14. The IR imaging system of claim 10, wherein the processing circuitry is configured to perform edge detection of the first and second.

15. The IR imaging system of claim 10, wherein the processing circuitry is configured to evaluate whether image data of the first and second images exceeds a threshold to determine whether the optical window is obscured.

16. The IR imaging system of claim 10, wherein the processing circuitry is configured to compare the first and second images from the respective first and second optical channels of the plurality of spatially and spectrally distinct optical channels and use differences between the first and second images caused by parallax to determine whether the optical window is obscured.

17. The IR imaging system of claim 10, wherein the first and second optical channels of the plurality of spatially and spectrally distinct optical channels are spatially distinct in a given direction, and wherein the processing circuitry is configured to compare image data from the first and second optical channels at a plurality of offsets along the given direction to detect whether the optical window is obscured.