Infrared camera for gas detection

• US 8,803,093 B2
• Filed: 06/02/2009
• Issued: 08/12/2014
• Est. Priority Date: 06/02/2009
• Status: Active Grant

• Current Assignee: Flir Systems AB (Teledyne Technologies Incorporated)
• Original Assignee: Flir Systems AB (Teledyne Technologies Incorporated)
• Inventors: Jnsson, Henrik
• Primary Examiner(s): Sung, Christine
• Application Number:
  US12/477,022
• Publication Number:
  US 20100301214A1
• Time in Patent Office: 1,897 Days
• Field of Search: 250/339.01
• US Class Current: 250/339.01
• CPC Class Codes: G01N 21/3518 Devices using gas filter correlation techniques; Devices using gas pressure modulation techniques

Abstract

An IR camera is disclosed, comprising two IR detectors for detecting a first and a second image of the imaged area. A beamsplitter is operable to split the incoming radiation into a first beam comprising a first wavelength spectrum and a second beam comprising a second wavelength spectrum different from the first wavelength spectrum. The first beam is received at the first IR detector and the second beam is received at the second IR detector. A processor is operable to calculate properties of the imaged area based on the first and the second image in relationship to each other. The information obtained may be used, for example, to detect the presence or identity of a gas or to determine the material properties of an imaged object.

Claims

1. An infrared (“

IR”

) camera comprising;

an optical system configured to receive incoming radiation in an IR wavelength range from an imaged area;

a first thermal IR detector;

a second thermal IR detector;

a first beamsplitter configured to transmit a first wavelength spectrum and reflect a second wavelength spectrum,

wherein the incoming radiation received through the optical system is split by the first beamsplitter into a first beam having the first wavelength spectrum that is transmitted through the first beamsplitter and a second beam having the second wavelength spectrum that is reflected from the first beamsplitter and is of a different wavelength spectrum than the first wavelength spectrum,

wherein the first and second beam represent a same scene of the imaged area,

wherein the first thermal IR detector is configured to receive the first beam and detect a first image of the imaged area based on the first beam, and

wherein the second thermal IR detector is configured to receive the second beam and detect a second image of the imaged area based on the second beam;

a processor operable to calculate properties of the imaged area based on a relationship of the first and the second images; and

a display, coupled to the processor, for viewing by a user of the camera,

wherein the camera is operable to detect a presence of a gas in the imaged area by comparing the second image to the first image to obtain a gas image indicating the presence of the gas in the image area, said gas having a particular gas wavelength range,

wherein the first beamsplitter is configured to split the incoming radiation so that the relationship between the gas wavelength range and the incoming IR wavelength range in the first beam is different from the relationship between the gas wavelength range and the incoming IR wavelength range in the second beam, and

wherein the camera is configured to present the obtained gas image on the display for viewing by the user.

2. The IR camera according to claim 1, wherein the first beamsplitter is operable to split the incoming radiation so that the first image has a stronger contribution of radiation in the wavelength range of the gas as compared to the contribution of radiation in the wavelength range of the gas in the second image and the second image has a stronger contribution of radiation outside the frequency spectrum of the gas as compared to the contribution of radiation in the frequency spectrum of the gas in the second image.

3. The IR camera according to claim 1, wherein the processor is operable to determine a first total energy registered by the first thermal IR detector, a second total energy registered by the second thermal IR detector, and a value of the temperature of an imaged object or an emissivity factor for the object, based on the first total energy and the second total energy.

4. The IR camera according to claim 1, wherein the processor is operable to determine a first total energy registered by the first thermal IR detector in the first wavelength spectrum, a second total energy registered by the second thermal IR detector in the second wavelength spectrum, and a value representative of a first emissivity factor of an imaged object based on the first total energy and a value representative of a second emissivity factor based on the second total energy.

5. The IR camera according to claim 4, wherein the processor is operable to determine the first emissivity factor and the second emissivity factor based on the first and second total energy, respectively, and a temperature of the imaged object.

6. The IR camera according to claim 4, wherein the processor is operable to determine a relationship between the first emissivity factor and the second emissivity factor.

7. The IR camera according to claim 1, further comprising:

a second beamsplitter configured to further split the first beam from the first beamsplitter into a reflected part having a third wavelength spectrum and a transmitted part having a fourth wavelength spectrum different from the third wavelength spectrum; and

a third thermal IR detector configured to receive the reflected part of the first beam and detect a third image of the imaged area based on the reflected part of the first beam,

wherein the first thermal IR detector is configured to receive the transmitted part of the first beam to detect the first image of the imaged area.

8. The IR camera according to claim 1, further comprising:

a second beamsplitter configured to further split the second beam from the first beamsplitter into a reflected part having a third wavelength spectrum and a transmitted part having a fourth wavelength spectrum different from the third wavelength spectrum; and

a third thermal IR detector configured to receive the reflected part of the second beam and detect a third image of the imaged area based on the reflected part of the second beam,

wherein the second thermal IR detector is configured to receive the transmitted part of the second beam to detect the second image of the imaged area.

9. The IR camera according to claim 8, wherein each beamsplitter is selectable according to a corresponding type of gas to be detected in the imaged area.

10. The IR camera according to claim 1,

further comprising one or more additional beamsplitters for splitting a beam into a reflected part and a transmitted part respectively having a different wavelength spectrum, wherein the first beamsplitter and the one or more additional beamsplitters are configured to selectively translate or rotate into and out of an optical path between the optical system and the thermal IR detectors.

11. A method of using an infrared (“

IR”

) camera, the method comprising;

receiving, through an optical system of the IR camera, incoming radiation in an IR wavelength range from an imaged area;

splitting the incoming radiation with a first beamsplitter into a first beam and a second beam based on a wavelength range of a gas to detect, by transmitting a first wavelength spectrum of the incoming radiation through the first beamsplitter as the first beam and by reflecting a second wavelength spectrum of the incoming radiation with the first beamsplitter as the second beam,

wherein the first wavelength spectrum is of a different wavelength spectrum than the second wavelength spectrum, and

wherein the first and the second beams represent a same scene of the imaged area;

receiving the first beam at first thermal IR detector of the IR camera to detect a first image;

receiving the second beam at a second thermal IR detector of the TR camera to detect a second image; and

performing calculations regarding the imaged area based on a relationship between the first and second images to detect a presence of a gas in the imaged area by comparing the second image to the first image to obtain a gas image indicating the presence of the gas in the imaged area; and

displaying the obtained gas image.

12. A method according to claim 11, wherein the second wavelength spectrum excludes the wavelength range of the gas and the wavelength range of the gas is a subset of the first wavelength spectrum.

13. The method according to claim 12, further comprising selecting the first beamsplitter from a plurality of different beamsplitters, wherein the first beamsplitter is selected to perform the splitting of the incoming radiation according to a corresponding type of gas to be detected.

14. The method according to claim 11 further comprising:

obtaining a visual image of the area; and

fusing the gas image with the visual image.

15. The method according to claim 11, further comprising:

determining a first total energy registered by the first thermal IR detector;

determining a second total energy registered by the second thermal IR detector; and

determining a value of the temperature of an imaged object or an emissivity factor for the object, based on the first total energy and the second total energy.

16. The method according to claim 11, further comprising:

determining a first total energy registered by the first thermal IR detector in the first wavelength spectrum;

determining a second total energy registered by the second thermal IR detector in the second wavelength spectrum; and

determining a value representative of a first emissivity factor of an imaged object based on the first total energy and a value representative of a second emissivity factor based on the second total energy.

17. The method according to claim 16, wherein determining the first emissivity factor and the second emissivity factor based on the first and second total energy, respectively, is also based on a temperature of the object.

18. The method according to claim 16, further comprising:

determining a relationship between the first emissivity factor and the second emissivity factor.

19. The method according to claim 11, further comprising:

selecting from the first beamsplitter and at least a second beamsplitter to perform the splitting of the incoming radiation according to a corresponding type of gas to be detected; and

determining if the corresponding type of gas is present in the imaged area based on the performing.

20. The method according to claim 11, further comprising:

splitting the first beam from the first beamsplitter into a reflected part having a third wavelength spectrum and a transmitted part having a fourth wavelength spectrum different from the third wavelength spectrum; and

receiving the reflected part of the first beam at a third thermal IR detector of the IR camera to detect a third image of the imaged area based on the reflected part of the first beam,

wherein the receiving the first beam to detect the first image is by receiving the transmitted part of the first beam from the second beamsplitter.