CMOS image sensor reading circuit and reading method

Abstract

The invention relates to a CMOS image sensor reading circuit, which comprises an analog-to-digital converter, and also comprises a variable gain amplifier, a comparator and a gain adjusting device, wherein the variable gain amplifier is suitable for receiving and adjusting pixel exposing voltage of the image sensor, and outputting the voltage to the analog-to-digital converter; the comparator is suitable for judging the pixel exposing voltage; and the gain adjusting device is suitable for receiving a judgment result output by the comparator, and adjusting an amplification factor of the variable gain amplifier according to an exposing voltage section where the exposing voltage is positioned. The invention also relates to a method for reading digital signals from pixels by the CMOS image sensor, which comprises the following steps: adjusting the pixel exposing voltage by the variable gain amplifier; converting analog voltage signals output by the variable gain amplifier into digital signals for output; judging the pixel exposing voltage; and adjusting the amplification factor of the variable gain amplifier according to the exposing voltage section where the exposing voltage is positioned. Under the conditions of different light intensities, both the reading circuit and the method can obtain clear images to meet the requirement of human eye on image quality.

Description

technical field [0001] The invention relates to the technical field of image processing, in particular to a complementary metal oxide semiconductor (CMOS) image sensor readout circuit and a readout method. Background technique [0002] A CMOS image sensor is a semiconductor device that converts an optical image into an electrical signal. The basic conversion process is: the pixels in the CMOS image sensor are exposed, and within a certain exposure time, the voltage on the pixels generates a linear voltage with different light intensities, and the subsequent readout circuit converts this voltage into a digital signal output. [0003] Typically, a CMOS image sensor uses a 10-bit analog-to-digital converter, so its digital output has an output data range of 10 bits. The human eye can see a dynamic range of about 10 6 ~10 8 lumen. Although humans cannot see this entire range of light at the same time, the maximum sensitivity that the human eye can perceive simultaneously is ...

AI Technical Summary

Problems solved by technology

[0005] The inventors of the present invention found that the structure of this readout circuit always linearly outputs the voltage value on the pixel after exposure under different light intensities, so the output values ​​of strong light and dark light have a large difference. After conversion by the analog-to-digital converter , the strong light output value can reach 1000, while the low light output value may only be tens of tens, so the image details are greatly lost in low light, which cannot meet the requirements of the human eye for image quality

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