Unit cells with avalanche photodiode detectors
AssigneeFLIR Systems, Inc.
InventorsJames T. Woolaway, John D. Schlesselmann
Life of this patent
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Abstract
Various techniques are disclosed for providing reference signals to image detectors in accordance with one or more embodiments of the invention. For example, in one or more embodiments, switched capacitors may be used to provide bias voltages to individual unit cells of a focal plane array such that the bias voltages are held by the unit cells over one or more integration periods while the unit cells are decoupled from an input line. As a result, the bias voltages may be free from noise incident on the input line and thus may more accurately bias the individual unit cells.
Claims22
A unit cell of a focal plane array, the unit cell comprising:
- a detector comprising an avalanche photodiode adapted to provide a detector signal in response to infrared light received by the detector;
- a first capacitor adapted to store a bias voltage while additional bias voltages are loaded into other unit cells of the focal plane array;
- a first switch adapted to connect the first capacitor to an input line to provide the bias voltage from the input line to the first capacitor and disconnect the first capacitor from the input line after the bias voltage is provided;
- a second capacitor adapted to store the bias voltage during at least one integration period of the focal plane array;
- a second switch adapted to provide the bias voltage from the first capacitor to the second capacitor prior to the at least one integration period;
- and
- an output node adapted to store an output voltage that changes in response to the detector signal and the bias voltage stored by the second capacitor.
A method of operating a focal plane array of an infrared camera, the method comprising:
- connecting a first capacitor of a unit cell of the focal plane array to an input line;
- providing a bias voltage from the input line to the first capacitor;
- disconnecting the first capacitor from the input line after the bias voltage is provided;
- storing the bias voltage at the first capacitor while additional bias voltages are loaded into other unit cells of the focal plane array;
- providing the bias voltage from the first capacitor to a second capacitor;
- storing the bias voltage at the second capacitor during at least one integration period of the focal plane array;
- biasing a detector with the bias voltage stored at the second capacitor during the at least one integration period, wherein the detector comprises an avalanche photodiode adapted to provide a detector signal in response to infrared light received by the detector;
- and
- storing at an output node an output voltage that changes in response to the detector signal and the bias voltage stored by the second capacitor.
Dependencies are inferred from the claim text.