Analogue to digital converter for image sensor readout
AssigneeTeledyne Innovaciones Microelectronicas Slu
InventorsJose Angel Segovia de la Torre, Ana Gonzalez Marquez, Rafael Dominguez Castro, Alexander Charlet, Alberto Villegas
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Abstract
An analogue to digital converter for converting the analogue output of a dual conversion gain pixel of an image sensor. The dual conversion gain pixel is operable to sequentially output a reset pixel value and a signal pixel value sequentially with both a first gain and a second gain different to the first gain. An image sensor comprising the analogue to digital converter, a system comprising the image sensor and a method are also described herein.
Claims14
An analogue to digital converter for converting an analogue output of a dual conversion gain pixel of an image sensor, wherein the dual conversion gain pixel is operable to sequentially output a reset pixel value and a signal pixel value sequentially with both a first gain and a second gain different to the first gain, wherein the analogue to digital converter comprises:
- analogue storage for storing the reset pixel value output with the first gain;
- a first converter stage arranged to sequentially sample a first analogue input indicative of a reset pixel value of the dual conversion gain pixel and a second analogue input indicative of a signal pixel value of the dual conversion gain pixel, wherein the first converter stage is configured to sequentially sample the first analogue input and the second analogue input and output a digital value indicative of a difference between the first input and the second input;
- and
- circuitry configured to sequentially provide the reset pixel value output with the second gain as a first input to the first converter stage and the signal pixel value output with the second gain as a second input to the first converter stage over a plurality of clock cycles of the first converter stage such that the first converter stage sequentially samples the first and second inputs and outputs a first digital value indicative of a difference between the reset pixel value output with the second gain and the signal pixel value output with the second gain, and
- wherein the circuitry is further configured to provide the reset pixel value output with the first gain and stored in the analogue storage as a third input to the first converter stage and the signal pixel value output with the first gain as a fourth input to the first converter stage over one clock cycle of the first converter stage and wherein the first converter stage is configured to sample the third and fourth inputs and output a differential signal indicative of a difference between the reset pixel value output with the first gain and the signal pixel value output with the first gain;
- and
- a second converter stage,
- wherein the circuitry is further configured to provide the differential signal to the second converter stage and wherein the second converter stage is configured to sample the differential signal and output a first gain digital value indicative of the difference between the reset pixel value output with the first gain and the signal pixel value output with the first gain.
A method of an analogue to digital converter for converting an analogue output of a dual conversion gain pixel of an image sensor, wherein the dual conversion gain pixel is operable to sequentially output a reset pixel value and a signal pixel value sequentially with both a first gain and a second gain different than the first gain, the method comprising:
- storing, in analogue storage, the reset pixel value output with the first gain;
- sequentially receiving, at a first converter stage, the reset pixel value output with the second gain as a first analogue input and the signal pixel value output with the second gain as a second analogue input;
- sequentially sampling, at the first converter stage, the first and second analogue inputs over a plurality of clock cycles of the first converter stage and outputting a first digital value indicative of a difference between the reset pixel value output with the second gain and the signal pixel value output with the second gain;
- receiving, at the first converter stage, the reset pixel value output with the first gain and stored in the analogue storage as a third analogue input and the signal pixel value output with the first gain as a further analogue input over one clock cycle of the first converter stage;
- sampling, at the first converter stage, the third and fourth analogue inputs and outputting a differential signal indicative of a difference between the reset pixel value output with the first gain and the signal pixel value output with the first gain;
- and
- sampling at a second converter stage the differential signal and outputting from the second converter stage a first gain digital value indicative of the difference between the reset pixel value output with the first gain and the signal pixel value output with the first gain.
Dependencies are inferred from the claim text.