Thermal imaging device
First Claim
1. A thermal imaging device including a detector array responsive to thermal infrared radiation, said detector array having a linearly-arrayed plurality of detector elements, a scanning device scanning a viewed scene across said plurality of detector elements, individually in response to incident infrared radiation said plurality of detector elements each providing a corresponding one of a plurality of detector-signals, said thermal imaging device comprising:
- an absolute value circuit providing a corresponding plurality of absolute-value signals each indicative of the respective absolute value of one of said plurality of detector-signals during a scan of said viewed scene across said detector, an averaging circuit providing an average-value signal indicative of the average of said plurality of absolute-value signals, and a median value compiler circuit providing a median-value signal indicative of the median of said plurality of absolute-value signals.
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Accused Products
Abstract
A thermal infrared imaging device (10) includes a thermal detector (50) having a linearly-arrayed plurality of spaced apart detector elements (50'"'"', 50", 50"'"'"', . . . ). A scene to be viewed is scanned across the detector (50) with successive fields of the scene shifted according the spacing between adjacent detector elements (50'"'"', 50", 50"'"'"', . . . ) in order to capture image information for the entire scene by interlacing of successive scan lines from the plurality of detector elements (50'"'"', 50", 50"'"'"', . . . ). Each complete scan of the viewed scene across the detector (50) creates an image field including a scan line for each detector element (50'"'"', 50", 50"'"'"', . . . ). Each scan line includes plural pixels, or picture elements of the viewed scene, each having a value indicative of the thermal infrared brightness of the viewed scene at the corresponding location along the scan line. An scan-line sum for each scan line is created by adding the absolute values of the pixel values for each scan line. The average of these scan-line sums is employed as a gain control factor to control the brightness of a visible image replicating the viewed scene. Further, the value of a median of the scan-line sums is used to limit gain variations which would otherwise be effected were the line-sum averages alone used to control the gain factor. Accordingly, even when a localized highly-radiant heat source (such as a fire) is within the field of view of the thermal imaging device, then in areas of the image away from the brightness caused by the fire the image does not go dark and a visible image good contrast is still maintained allowing features of the image to be viewed.
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Citations
16 Claims
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1. A thermal imaging device including a detector array responsive to thermal infrared radiation, said detector array having a linearly-arrayed plurality of detector elements, a scanning device scanning a viewed scene across said plurality of detector elements, individually in response to incident infrared radiation said plurality of detector elements each providing a corresponding one of a plurality of detector-signals, said thermal imaging device comprising:
- an absolute value circuit providing a corresponding plurality of absolute-value signals each indicative of the respective absolute value of one of said plurality of detector-signals during a scan of said viewed scene across said detector, an averaging circuit providing an average-value signal indicative of the average of said plurality of absolute-value signals, and a median value compiler circuit providing a median-value signal indicative of the median of said plurality of absolute-value signals.
- View Dependent Claims (2, 3, 4, 5)
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6. A thermal imaging device including a detector array responsive to thermal infrared radiation, said detector array having a linearly-arrayed plurality of spaced-apart detector elements defining cooperatively a length dimension for said detector array, a scanning device scanning a viewed scene across said plurality of detector elements in a direction generally perpendicular to said length dimension, each of said plurality of detector elements providing a corresponding individual electrical signal indicative of the thermal infrared radiation incident thereon, individual detector elements in said plurality of detector elements varying from one another, said thermal imaging device comprising:
- an individual direct-current electrical connection from each one of said plurality of detector elements to a corresponding one of a plurality of fixed-gain analog amplifiers, said plurality of fixed-gain analog amplifiers each having electrical connection to a multiplexer for putting out a serial stream of analog signals indicative of the thermal infrared radiation flux incident upon said detector array, a compensation circuit responding to differences in electrical signals from identified ones of said plurality of detector elements which have scanned the same portion of said viewed scene to provide a respective compensation signal for said identified detector elements, and an electrical circuit applying said respective compensation signals to the ones of said plurality of fixed-gain amplifiers connected with the respective ones of said plurality of detector elements so as to modify the gain thereof to minimize said differences, an absolute value circuit providing a corresponding plurality of absolute-value signals each indicative of the respective absolute value of one of said plurality of detector-signals during a scan of said viewed scene across said detector, an averaging circuit providing an average-value signal indicative of the average of said plurality of absolute-value signals, and a median value compiler circuit providing a median-value signal indicative of the median of said plurality of absolute-value signals, a variable-gain analog amplifier receiving said serial stream of analog signals indicative of the thermal infrared radiation flux incident upon said detector array, and a gain correction circuit receiving said average-value signal and responsively providing a gain-correction signal controlling the gain value of said variable-gain analog amplifier.
- View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. A method of operating a thermal imaging device, said thermal imaging device including a detector array responsive to thermal infrared radiation, said detector array having a linearly-arrayed plurality of spaced apart detector elements cooperatively defining a length dimension for said detector array, a scanning device scanning a viewed scene across said plurality of detector elements in plural scans with relative transpositions of said viewed scene along the length dimension of said detector array in successive scans so as to capture image information from all of said viewed scene with said spaced apart plurality of detector elements, individually in response to incident infrared radiation said plurality of detector elements each providing a corresponding one of a plurality of electrical detector-signals, said method comprising:
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providing an absolute value circuit; using said absolute value circuit to provide a corresponding plurality of absolute-value signals each indicative of the respective absolute value of one of said plurality of detector-signals during a particular scan of said viewed scene across said detector array; providing an averaging circuit; using said averaging circuit to provide an average-value signal indicative of the average of said plurality of absolute-value signals; providing a median value compiler circuit; using said median value compiler circuit to provide a median-value signal indicative of the median of said plurality of absolute-value signals; providing a gain correction circuit receiving said average-value signal and responsively providing a gain-correction signal; providing a variable-gain analog amplifier; using said variable-gain analog amplifier to receive and amplify said plurality of electrical detector-signals; and using said gain-correction signal to control a gain value of said variable-gain analog amplifier. - View Dependent Claims (14, 15, 16)
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Specification