Apparatus and methods for dark level compensation in image sensors using dark pixel sensor metrics
OwnerJaejin Parkinventor
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Abstract
An image sensor comprises a plurality of pixel sensors, e.g., CMOS pixel sensors, including a plurality of dark pixels. A dark level compensation circuit that controls an offset applied to an image signal generated by a pixel sensor responsive to an aggregate dark level metric, e.g., a mean dark level, derived from dark pixel image signals produced by the dark pixel sensors. For example, the dark level compensation circuit for CMOS image sensor using a column parallel architecture may generate an offset control signal that varies an offset of a reference signal used by an analog to digital converter (ADC) circuit that converts an analog image signal from a pixel sensor to a dark level compensated digital image signal.
Claims25
A complementary metal oxide semiconductor (CMOS) image sensor, comprising:
- a CMOS pixel sensor array comprising a plurality of rows of CMOS pixel sensors, each row of CMOS pixel sensors comprising at least one dark pixel sensor;
- and
- a dark level compensation circuit that controls an offset applied to an image signal generated by a CMOS pixel sensor of the CMOS pixel array responsive to an aggregate dark level metric derived from dark pixel image signals produced by the dark pixel sensors.
An image sensor, comprising:
- a plurality of pixel sensors that produce respective analog image signals, the plurality of pixel sensors including a plurality of dark pixel sensors;
- an analog to digital converter (ADC) circuit that receives an analog image signal generated by a pixel sensor of the plurality of pixel sensors and that produces a digital image signal therefrom subject to an offset controlled by an offset control signal;
- and
- a dark level compensation circuit that generates the offset control signal responsive to analog image signals produced by the dark pixel sensors.
A method of operating an image sensor, comprising:
- generating dark pixel image signals from dark pixel sensors on multiple rows of a CMOS pixel sensor array;
- generating an offset control signal from the dark pixel image signals;
- producing an image signal from a pixel sensor of the CMOS pixel sensor array;
- and
- applying an offset to the image signal responsive to the offset control signal.
A method of operating an image sensor comprising a plurality of pixel sensors, the method comprising:
- generating dark pixel image signals from a plurality of dark pixel sensors included in the plurality of pixel sensors;
- generating an offset control signal from the dark pixel image signals;
- applying the offset control signal to an analog to digital converter (ADC) circuit that receives an analog image signal produced by a pixel sensor of the plurality of pixel sensors to produce a dark level compensated digital image signal.
Dependencies are inferred from the claim text.