Digital offset corrector
AssigneeLockheed-Martin IR Imaging Systems, Inc.
InventorNeal R. Butler
Life of this patent
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Abstract
An offset corrector for a focal plane array. A bolometer array configured in a row and column readout format has dedicated column circuits to measure the resistance of each bolometer in the column. A high speed on-chip analog to digital converter converts the analog sensor signal to a digital representation. Since the response of each bolometer varies, an offset controller, connected to the output of the analog to digital converter, corrects the digital representation for variations in individual bolometer response. Each pixel has a corresponding dynamically computed offset stored in the memory. The offset is computed when a chopper or shutter blocks radiation from the focal plane array. The focal plane array is temperature stabilized to a predetermined temperature to keep bolometer response within a predetermined bandwidth.
Claims19
Apparatus comprising:
- at least one sensor to detect radiation and to output image signals based on the detected radiation;
- and
- offset correction circuitry to compensate errors in the image signals and to output corrected image signals,
- wherein the sensor and at least a portion of the offset correction circuitry are monolithically integrated on a single semiconductor substrate, and
- wherein the offset correction circuitry further includes means for providing a time-varying compensation signal for each at least one sensor to compensate the errors in the image signals.
Apparatus comprising:
- at least one sensor to detect radiation and to output image signals based on the detected radiation;
- and
- offset correction circuitry to compensate errors in the image signals and to output corrected image signals,
- wherein the sensor and at least a portion of the offset correction circuitry are monolithically integrated on a single semiconductor substrate,
- wherein the offset correction circuitry includes means for receiving digital offset data, wherein:
- the at least one sensor includes a plurality of sensors;
- and
- the offset correction circuitry includes a digital to analog converter to compensate non-uniformities of the sensors, and
- wherein the offset correction circuitry further includes a nonlinear compensating voltage supply to compensate changes in the image signals due to current-induced heating of the at least one sensor.
Apparatus comprising:
- at least one sensor to detect radiation and to output image signals based on the detected radiation;
- and
- offset correction circuitry to compensate errors in the image signals and to output corrected image signals,
- wherein the sensor and at least a portion of the offset correction circuitry are monolithically integrated on a single semiconductor substrate,
- wherein the offset correction circuitry includes means for receiving digital offset data,
- wherein the means for receiving digital offset data includes a digital to analog converter, and
- wherein the offset correction circuitry further includes:
- an amplifier to receive the image signals and to output amplified image signals;
- and
- an offset capacitor, coupled to an output of the amplifier and responsive to an analog signal output from the digital to analog converter, to add an offset signal to the amplified image signals so as to provide the corrected image signals.
Dependencies are inferred from the claim text.