Infrared imaging system employing on-focal plane nonuniformity correction
First Claim
1. An infrared imaging system, comprising:
- an infrared focal plane array comprising;
a plurality of infrared detector elements arranged in an array;
a readout circuit electrically coupled to the plurality of detector elements and comprising means for biasing the plurality of detector elements so as to provide separate detection signals corresponding to each detector element in the array, in response to incident infrared radiation and means for separately correcting offsets in the detection signals Provided provided from the plurality of elements in the detector array to compensate for nonuniformities in the detector elements, wherein said means for correcting comprises;
a correction circuit including a plurality of parallel connected circuit elements; and
means for selectively electrically connecting said circuit elements into the detector readout circuit in response to stored offset correction values; and
output means for providing the corrected detection signals as an output of the focal plane array;
means for storing a plurality of offset correction values corresponding to the plurality of detector elements; and
means for providing the offset correction values to said means for correcting.
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Abstract
An infrared imaging system having a focal plane array including an array of detector elements and a readout circuit and including nonuniformity correction circuitry on the focal plane array. The individual detector elements correspond to pixels of an infrared scene to be imaged. Offsets in detection signals from each pixel arising from nonuniformities in the individual detector elements in the array are corrected by storing offset correction values for each detector element and using the stored offset values to control correction circuitry as the respective detector element signals are read out. The detector array and readout circuit are preferably formed as a monolithic or hybrid structure and the offset correction is provided on the focal plane array prior to signal amplification and analog to digital conversion.
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Citations
54 Claims
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1. An infrared imaging system, comprising:
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an infrared focal plane array comprising;
a plurality of infrared detector elements arranged in an array;
a readout circuit electrically coupled to the plurality of detector elements and comprising means for biasing the plurality of detector elements so as to provide separate detection signals corresponding to each detector element in the array, in response to incident infrared radiation and means for separately correcting offsets in the detection signals Provided provided from the plurality of elements in the detector array to compensate for nonuniformities in the detector elements, wherein said means for correcting comprises;
a correction circuit including a plurality of parallel connected circuit elements; and
means for selectively electrically connecting said circuit elements into the detector readout circuit in response to stored offset correction values; and
output means for providing the corrected detection signals as an output of the focal plane array;
means for storing a plurality of offset correction values corresponding to the plurality of detector elements; and
means for providing the offset correction values to said means for correcting. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. An infrared imaging system, comprising:
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an infrared focal plane array comprising;
a plurality of infrared detector elements arranged in an array;
a readout circuit electrically coupled to the plurality of detector elements and comprising a plurality of readout cells equal in number to the plurality of detector elements, means for biasing the plurality of detector elements so as to provide separate detection signals corresponding to each detector element in the array, in response to incident infrared radiation and means for separately correcting offsets in the detection signals provided from the plurality of elements in the detector array to compensate for nonuniformities in the detector elements, wherein said means for correcting comprises an offset correction and circuit in each readout cell of the readout circuit and wherein each offset correction circuit comprises a plurality of parallel connected circuit elements and means for selectively electrically connecting said circuit elements into the readout cell in response to a stored offset correction value corresponding to said readout cell; and
output means for providing the corrected detection signals as an output of the focal plane array;
means for storing a plurality of offset correction values corresponding to the plurality of detector elements; and
means for providing the offset correction values to said means for correcting.
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27. An infrared focal plane array, comprising:
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a plurality of detector elements configured in a two dimensional array; and
a readout circuit electrically coupled to said plurality of detector elements and structurally integrated therewith, said readout circuit comprising;
a sample and hold capacitor;
means for biasing the detector elements so as to provide an analog detection signal from each detector element corresponding to the infrared radiation incident thereon, wherein the analog detection signal is a voltage signal provided at a sample node coupled to the sample and hold capacitor; and
means for correcting the analog detection signal from each detector element by a discrete offset correction and providing a corrected analog detection signal, wherein the discrete offset correction varies from detector element to detector element and comprises an offset correction voltage added to, or subtracted from, the analog detection signal, wherein said means for correcting subtracts or adds a variable amount of charge from said sample and hold capacitor to provide a corrected voltage signal at said sample node, and wherein said means for correcting comprises a plurality of capacitors connected between said sample node and a reference voltage and a corresponding plurality of switches coupled in series with each respective capacitor and said reference voltage, wherein said plurality of switches are selectively turned on or off to provide a desired amount of discrete offset correction for each detector element. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34)
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35. An infrared focal plane array, comprising:
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a plurality of detector elements configured in a two dimensional array; and
a readout circuit electrically coupled to said plurality of detector elements and structurally integrated therewith, said readout circuit comprising;
a sample and hold capacitor;
means for biasing the detector elements so as to provide an analog detection signal from each detector element corresponding to the infrared radiation incident thereon, wherein the analog detection signal is a voltage signal provided at a sample node coupled to the sample and hold capacitor; and
means for correcting the analog detection signal from each detector element by a discrete offset correction and providing a corrected analog detection signal, wherein the discrete offset correction varies from detector element to detector element and comprises an offset correction voltage added to, or subtracted from, the voltage signal, wherein said means for correcting subtracts or adds a variable amount of charge from said sample and hold capacitor to provide a corrected voltage signal at said sample node, and wherein said means for correcting comprises a plurality of parallel connected constant current sources connected between said sample node and a reference voltage and a plurality of switches corresponding to said plurality of constant current sources and respectively coupled in series therewith.
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36. An infrared imaging system, comprising:
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an infrared focal plane array comprising;
a plurality of infrared detector elements arranged in an array;
a readout circuit electrically coupled to the plurality of detector elements and comprising means for biasing the plurality of detector elements so as to provide separate detection signals corresponding to each detector element in the array, in response to incident infrared radiation and means for separately correcting offsets in the detection signals provided from the plurality of elements in the detector array to compensate for nonuniformities in the detector elements, wherein said means for correcting comprises;
a correction circuit including a plurality of circuit elements; and
means for selectively electrically connecting said circuit elements into the detector readout circuit in response to stored offset correction values; and
output means for providing the corrected detection signals as an output of the focal plane array;
means for storing a plurality of offset correction values corresponding to the plurality of detector elements; and
means for providing the offset correction values to said means for correcting. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47)
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48. An infrared imaging system, comprising:
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an infrared focal plane array comprising;
a plurality of infrared detector elements arranged in an array;
a readout circuit electrically coupled to the plurality of detector elements and comprising a plurality of readout cells equal in number to the plurality of detector elements, means for biasing the plurality of detector elements so as to provide separate detection signals corresponding to each detector element in the array, in response to incident infrared radiation and means for separately correcting offsets in the detection signals provided from the plurality of elements in the detector array to compensate for nonuniformities in the detector elements, wherein said means for correcting comprises an offset correction circuit in each readout cell of the readout circuit and wherein each offset correction circuit comprises a plurality of circuit elements and means for selectively electrically connecting said circuit elements into the readout cell in response to a stored offset correction value corresponding to said readout cell; and
output means for providing the corrected detection signals as an output of the focal plane array;
means for storing a plurality of offset correction values corresponding to the plurality of detector elements; and
means for providing the offset correction values to said means for correcting.
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49. An infrared focal plane array, comprising:
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a plurality of detector elements configured in a two dimensional array; and
a readout circuit electrically coupled to said plurality of detector elements and structurally integrated therewith, said readout circuit comprising;
a sample and hold capacitor;
means for biasing the detector elements so as to provide an analog detection signal from each detector element corresponding to the infrared radiation incident thereon, wherein the analog detection signal is a voltage signal provided at a sample node coupled to the sample and hold capacitor; and
means for correcting the analog detection signal from each detector element by a discrete offset correction and providing a corrected analog detection signal, wherein the discrete offset correction varies from detector element to detector element and comprises an offset correction voltage added to, or subtracted from, the analog detection signal, wherein said means for correcting subtracts or adds a variable amount of charge from said sample and hold capacitor to provide a corrected voltage signal at said sample node, and wherein said means for correcting comprises a plurality of circuit elements connected between said sample node and a reference voltage and a corresponding plurality of switches coupled in series with each respective circuit element and said reference voltage, wherein said plurality of switches selectively provide a desired amount of discrete offset correction for each detector element. - View Dependent Claims (50, 51, 52, 53)
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54. An infrared focal plane array, comprising:
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a plurality of detector elements configured in a two dimensional array; and
a readout circuit electrically coupled to said plurality of detector elements and structurally integrated therewith, said readout circuit comprising;
a sample and hold capacitor;
means for biasing the detector elements so as to provide an analog detection signal from each detector element corresponding to the infrared radiation incident thereon, wherein the analog detection signal is a voltage signal provided at a sample node coupled to the sample and hold capacitor; and
means for correcting the analog detection signal from each detector element by a discrete offset correction and providing a corrected analog detection signal, wherein the discrete offset correction varies from detector element to detector element and comprises an offset correction voltage added to, or subtracted from, the voltage signal, wherein said means for correcting subtracts or adds a variable amount of charge from said sample and hold capacitor to provide a corrected voltage signal at said sample node, and wherein said means for correcting comprises a plurality of constant current sources connected between said sample node and a reference voltage and a plurality of switches corresponding to said plurality of constant current sources and respectively coupled in series therewith.
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Specification