Image sensor readout circuit and readout method using improved gain ADC

Abstract

The invention discloses an ADC capable of improving gain. The circuit comprises a gain amplification unit, a comparator and a counter. Wherein the gain amplification unit comprises a sampling circuitand a switched capacitor amplification circuit; the switched capacitor amplifying circuit comprises a capacitor C1, a capacitor C2, a switch Kr and an amplifier; wherein the first input end of the amplifier is connected with a reference signal; a second input end of the amplifier is simultaneously connected with a sampling capacitor C1, a sampling capacitor C2 and one end of a switch Kr; the otherend of the sampling capacitor C1 is connected with the sampling circuit, the other end of the sampling capacitor C2 and the other end of the switch Kr are connected with the output end of the amplifier, the output end of the amplifier is connected with the comparator, and the output end of the comparator is connected with the counter. According to the image sensor reading circuit and reading method using the ADC capable of improving the gain, the final image noise level is low, the dynamic range and the signal-to-noise ratio are improved, and therefore the image quality of an image sensor under low illumination is improved.

Description

technical field [0001] The invention relates to the field of image sensors, in particular to an image sensor readout circuit and a readout method using an ADC with increased gain. Background technique [0002] CMOS Image Sensors (CIS) have been widely used in imaging fields such as video, surveillance, industrial manufacturing, automobiles, and home appliances. The structure of the CIS mainstream readout circuit is based on the column-level single-slope analog-to-digital converter (SS-ADC). The function of the SS-ADC is to compare the signal to be quantized with a ramp reference signal. The result of the comparison is The final quantization is performed by a counter to obtain an N-bit binary digital quantity. Generally, in a traditional readout circuit, the output of the pixel unit is compared with a reference ramp (RAMP) signal input to the comparator, and the output judgment result of the comparator is used as an indication for the ADC counter to stop counting to ensure c...

AI Technical Summary

Problems solved by technology

However, under low illumination, the original signal amplitude is small and the noise level is relatively high. The digital gain Dv multiplies all the noise (image noise and ADC noise), which degrades the CIS image quality.

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