Thermography camera configured for gas leak detection
First Claim
1. A camera system comprising:
- means for generating a corrected scene image signal comprising a series of signals corresponding with irradiance values at a plurality of locations of a scene image;
means for refreshing the corrected scene image signal at a video frame refresh rate;
a temporal filter memory for storing a temporally filtered scene image therein, said temporally filtered scene image comprising image signals corresponding with a temporal characteristic of irradiance values at each of the plurality of locations of the scene image over a selected time period;
a temporal filter for receiving the corrected scene image and the temporally filtered scene image therein, for comparing the corrected scene image with the temporally filtered scene image, and for updating the temporally filtered scene image according to a temporal weighting factor based on a difference between corrected image signal values and temporally filtered image signal values and for storing an updated temporally filtered scene image in the temporal filter memory; and
,an image difference calculator for receiving the corrected scene image signal and the updated temporally filtered scene image signal therein, for scaling the updated temporally filtered scene image signal by a scaling factor and for subtracting the scaled updated temporally filtered scene image from the corrected scene image to generate a difference scene image signal comprising a series of image signals corresponding with each of the plurality of locations of the scene image.
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Abstract
A portable thermography camera system (100) renders a video image of a survey scene over a narrow spectral bandwidth corresponding with an absorption band of a gas to be detected in the video image. The camera system forms a scene image onto a focal plane array (108) and generates a corrected image signal (162) corresponding with irradiance values at a plurality of locations of the scene image. The camera system further generates a temporally filtered image signal (168) corresponding with a temporal characteristics of the image signal (162) over a selected number of prior image frames. A difference block (166) reduces the temporally filtered image signal (168) by a scaling factor and produces a difference image by subtracting the scaled temporally filtered image signal from the corrected image signal (162). The displayed difference signal improves the visibility of the gas to be detected.
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Citations
27 Claims
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1. A camera system comprising:
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means for generating a corrected scene image signal comprising a series of signals corresponding with irradiance values at a plurality of locations of a scene image; means for refreshing the corrected scene image signal at a video frame refresh rate; a temporal filter memory for storing a temporally filtered scene image therein, said temporally filtered scene image comprising image signals corresponding with a temporal characteristic of irradiance values at each of the plurality of locations of the scene image over a selected time period; a temporal filter for receiving the corrected scene image and the temporally filtered scene image therein, for comparing the corrected scene image with the temporally filtered scene image, and for updating the temporally filtered scene image according to a temporal weighting factor based on a difference between corrected image signal values and temporally filtered image signal values and for storing an updated temporally filtered scene image in the temporal filter memory; and
,an image difference calculator for receiving the corrected scene image signal and the updated temporally filtered scene image signal therein, for scaling the updated temporally filtered scene image signal by a scaling factor and for subtracting the scaled updated temporally filtered scene image from the corrected scene image to generate a difference scene image signal comprising a series of image signals corresponding with each of the plurality of locations of the scene image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for rendering a video image of a survey scene comprising the steps of:
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forming a scene image onto a focal plane array; generating a corrected scene image signal comprising a series of signals corresponding with irradiance values at a plurality of locations of the scene image and continuously updating the scene image signal at a video frame rate; for each scene image signal, generating a temporally filtered image signal based on temporal characteristics of irradiance values at each of the plurality of locations of the scene image over a selected number of previous video frames; storing the temporally filtered image signal in a temporal filter memory block; multiplying the temporally filtered image signal by a scaling factor to reduce the temporally filtered image signal at each of the plurality of locations of the scene image thereby generating a scaled temporally filtered image signal; and
,generating a difference image signal by subtracting the scaled temporally filtered image signal from the scene image signal. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
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23. A gas leak detection camera comprising:
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a lens element for collecting radiation from a survey scene and forming a scene image of the survey scene at a focal plane of the lens element; an image sensor disposed at the focal plane of the lens element comprising a plurality of photosensitive elements disposed at a plurality of locations over the scene image for generating analog signals corresponding with irradiance values at each of the plurality of locations of a scene image, wherein the image sensor has a spectral responsivity that includes wavelengths of an absorption band of a gas to be detected; read out electronics for reading out the analog signals and refreshing the analog scene signals at a video frame rate; a spectral band pass filter disposed between the lens element and the image sensor for limiting the spectral bandwidth of the scene image to a spectral bandwidth approximately corresponding with wavelengths of an absorption band of the gas to be detected; an optical signal processor configured to convert the analog signals to a digital scene image signal, to generate a temporally filtered image signal corresponding with temporal characteristics of a plurality of prior digital scene images, to produce a scaled temporally filtered image by reducing the temporally filtered image by a scaling factor, and to generate a difference image by subtract the scaled temporally filtered image from the digital scene image; a digital data storage module in communication with the optical signal processor for storing the temporally filtered image therein; and
,a display device for displaying the difference image. - View Dependent Claims (24, 25, 26, 27)
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Specification