Image sensor with capacitor randomization for column gain
AssigneeOmniVision Technologies, Inc.
InventorsHiroaki Ebihara, Rui Wang, John Brummer, Shan Chen
Life of this patent
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Abstract
A pixel cell readout circuit includes a bitline input stage coupled to a bitline to receive an image signal from a pixel cell. A capacitor ratio circuit is coupled to the bitline input stage. A gain of the bitline input stage is responsive to a capacitor ratio provided by the capacitor ratio circuit to the bitline input stage. A switch control circuit is coupled to receive a gain signal. The switch control circuit is coupled to generate a randomized pattern selection signal coupled to be received by the capacitor ratio circuit to select the capacitor ratio provided by the capacitor ratio circuit in response to the gain signal.
Claims40
A pixel cell readout circuit, comprising:
- a bitline input stage coupled to a bitline to receive an image signal from a pixel cell;
- a capacitor ratio circuit coupled to the bitline input stage, wherein a gain of the bitline input stage is responsive to a capacitor ratio provided by the capacitor ratio circuit to the bitline input stage, wherein the capacitor ratio circuit comprises:
- a plurality of capacitors coupled to a first node of the capacitor ratio circuit that is coupled to an input of the bitline input stage, wherein a number of the plurality of capacitors is equal to m;
- and
- a plurality of switches, wherein each one of the plurality of switches is coupled to a respective one of the plurality of capacitors, wherein each one of the plurality of switches is configured to independently couple the respective one of the plurality of capacitors to either a second node or a third node of the capacitor ratio circuit in response to the randomized pattern selection signal from a switch control circuit;
- and
- the switch control circuit coupled to receive a gain signal, wherein the switch control circuit is coupled to generate the randomized pattern selection signal coupled to be received by the capacitor ratio circuit to select the capacitor ratio provided by the capacitor ratio circuit in response to the gain signal.
An imaging system, comprising:
- a pixel array including a plurality of pixel cells arranged in rows and columns, wherein each one of the pixel cells is coupled to generate an image signal in response to incident light;
- a control circuit coupled to the pixel array to control operation of the pixel array;
- and
- a readout circuit coupled to the pixel array to read out the image signals from the pixel array through bitlines, wherein the readout circuit comprises:
- a bitline input stage coupled to a bitline to receive an image signal from a pixel cell;
- a capacitor ratio circuit coupled to the bitline input stage, wherein a gain of the bitline input stage is responsive to a capacitor ratio provided by the capacitor ratio circuit to the bitline input stage, wherein the capacitor ratio circuit comprises:
- a plurality of capacitors coupled to a first node of the capacitor ratio circuit that is coupled to an input of the bitline input stage, wherein a number of the plurality of capacitors is equal to m;
- and
- a plurality of switches, wherein each one of the plurality of switches is coupled to a respective one of the plurality of capacitors, wherein each one of the plurality of switches is configured to independently couple the respective one of the plurality of capacitors to either a second node or a third node of the capacitor ratio circuit in response to the randomized pattern selection signal from the switch control circuit;
- and
- the switch control circuit coupled to receive a gain signal, wherein the switch control circuit is coupled to generate the randomized pattern selection signal coupled to be received by the capacitor ratio circuit to select the capacitor ratio provided by the capacitor ratio circuit in response to the gain signal.
Dependencies are inferred from the claim text.