# US 12,000,776 B2 · Window obscuration sensors for mobile gas and chemical imaging cameras

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- Number: US 12,000,776 B2
- Document ID: US12000776B2
- Status: Granted
- Kind: B2
- Application number: 18/179,879
- Filed: 2023-03-07
- Published: 2023-08-03
- Granted: 2024-06-04
- Earliest claimed: 2017-11-09
- Assignees: Rebellion Photonics, Inc.
- Applicants: Rebellion Photonics, Inc.
- Inventors: Ryan Mallery; Ohad Israel Balila; Robert Timothy Kester
- Web page: https://patentgrep.com/patent/US12000776B2

## CPC

- G01N 21/3504: for analysing gases, e.g. multi-gas analysis
- G01J 3/0208: {using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction}
- G01J 3/0213: {using attenuators}
- G01J 3/0264: {Electrical interface; User interface}
- G01J 3/0291: {Housings; Spectrometer accessories; Spatial arrangement of elements, e.g. folded path arrangements}
- G01J 3/0294: {Multi-channel spectroscopy}
- G01J 3/0297: {Constructional arrangements for removing other types of optical noise or for performing calibration}
- G01J 3/2823: {Imaging spectrometer}
- G01J 5/0014: {for sensing the radiation from gases, flames}
- G01J 5/0806: Focusing or collimating elements, e.g. lenses or concave mirrors
- G01N 21/15: Preventing contamination of the components of the optical system or obstruction of the light path
- G01N 21/314: {with comparison of measurements at specific and non-specific wavelengths (dual wavelength spectrometry G01J3/427)}
- H04N 23/20: for generating image signals from infrared radiation only
- G01J 3/0256: {Compact construction}
- G01J 3/027: {Control of working procedures of a spectrometer; Failure detection; Bandwidth calculation}
- G01J 2003/2806: {Array and filter array}
- G01N 2021/157: {Monitoring by optical means}
- G01N 2021/1795: {Atmospheric mapping of gases}
- G01N 2021/3531: {without instrumental source, i.e. radiometric}
- G01N 2201/0221: Portable; cableless; compact; hand-held
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## 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

### Claim 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 is in focus at the optical window to detect an obscuration of the optical window that may degrade operation of the IR imaging system.

### Claim 2 (depends on 1)

The IR imaging system of claim 1, wherein the first optical channel out of the plurality of spatially and spectrally distinct optical channels has a focus distance of less than 2 meters and other optical channels of the plurality of optical channels have a focus distance of greater than 10 meters.

### Claim 3 (depends on 1)

The IR imaging system of claim 1, wherein at least some of the other optical channels of the plurality of spatially and spectrally distinct optical channels have focus distances at least 5 meters greater than a focus distance of the first optical channel.

### Claim 4 (depends on 1)

The IR imaging system of claim 1, wherein the first optical channel out of the plurality of spatially and spectrally distinct 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 spatially and spectrally distinct optical channels to detect whether the optical window obscured.

### Claim 5 (depends on 1)

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 the obscuration that may degrade operation of the IR imaging system.

### Claim 6 (depends on 5)

The IR imaging system of claim 5, wherein:
a second optical channel out of the plurality of spatially and spectrally distinct 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 the obscuration that may degrade operation of the IR imaging system.

### Claim 7 (depends on 1)

The IR imaging system of claim 1, wherein the optical window is embedded in the housing or is in an opening in the housing.

### Claim 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 an obscuration is present.

### Claim 9 (depends on 8)

The IR imaging system of claim 8, wherein said processing unit is configured to provide a window obscuration alert after determining that the obscuration is present that may degrade operation of the IR imaging system.

### Claim 10 (depends on 8)

The IR imaging system of claim 8, wherein said processing unit is configured to compensate for effects of attenuation due to the obscuration when analyzing the infrared image data to detect the target species.

### Claim 11 (depends on 8)

The IR imaging system of claim 8, wherein the processing unit containing the processor is configured to determine whether the obscuration is present that may degrade operation of the IR imaging 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.

### Claim 12

A method of detecting obscuration of an optical window in an infrared (IR) imaging system, the method comprising:
with a processing circuitry, receiving a first image from a first optical channel in a 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 an obscuration of the optical window that may degrade operation of the IR imaging system.

### Claim 13 (depends on 12)

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 IR imaging system.

### Claim 14 (depends on 12)

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 IR imaging system.

### Claim 15 (depends on 12)

The method of claim 12, 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.

### Claim 16 (depends on 12)

The method of claim 12, 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.

### Claim 17 (depends on 12)

The method of claim 12, further comprising:
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.

### Claim 18 (depends on 12)

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.

### Claim 19 (depends on 12)

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 IR imaging system.

### Claim 20 (depends on 12)

The method of claim 12, further comprising detecting a target species based on image data from said plurality of optical channels.