cmos active pixel image sensor and its calibration method

Abstract

The invention provides a CMOS active pixel image sensor and a calibrating method thereof. The CMOS active pixel image sensor comprises a pixel array formed by a plurality of CMOS active pixels. Each pixel comprises a photosensor generating photocurrent under irradiation of incident light, an amplifier the input end of which is coupled with the photosensor, the amplifier being used for amplifying the photocurrent generated by the photosensor, and an integrating capacitor which is coupled between the input end and the output end of the amplifer and used for integration of the photocurrent amplified by the amplifier and for acquisition of integrating voltage, wherein the integrating capacitor is formed via parasitic coupling between metal layers or polycrystalline silicon layers formed in the manufacturing process of the CMOS active pixel image sensor. According to the invention, the integrating capacitor with low capacitance is formed via parasitic coupling between metal layers or polycrystalline silicon layers formed in the manufacturing process of the CMOS active pixel image sensor, so that the sensitivity of the CMOS active pixel image sensor is remarkably increased.

Description

technical field [0001] The invention relates to the field of image sensors, in particular to a CMOS active pixel image sensor and a calibration method thereof. Background technique [0002] Complementary metal oxide semiconductor (CMOS) image sensor (CIS) has become the mainstream of imaging technology due to its small size, low power consumption and low cost, and is widely used in optical mice, digital cameras, videophones, Smartphones and more. [0003] For CMOS image sensors, sensitivity and noise are two important parameters that usually measure the level of a digital image sensor, and since the fixed pattern noise (FPN) in the noise is constant for each frame, it is a bit like passing through the grid Looking at things, so fixed pattern noise reduction is more valued than transient noise reduction. [0004] The existing CIS technology is a CMOS image sensor composed of a pixel array (pixel array), and the pixel array is formed by arranging many pixel units. The genera...

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Problems solved by technology

[0008] The technical problem to be solved by the present invention is to provide a CMOS active pixel image sensor and its calibration method, which aims at the problems caused by the large integral capacitance existing in the current CMOS active pixel image sensor based on three transistors or four transistors. For the problem of low sensitivity of CMOS image sensors, a small integral capacitor formed by parasitic coupling between metal layers or between polysilicon layers in the manufacturing process of CMOS active pixel image sensors is proposed as an integral capacitor in CMOS image sensors to improve CMOS Sensitivity of active pixel image sensor; In addition, the present invention can increase the mismatch between active pixel and thereby increase the fixed pattern noise problem of CMOS active pixel image sensor for small parasitic integration capacitor again, has proposed in every A pixel is configured with a switch to introduce a known calibration current to the pixel so as to accurately measure the offset and fixed pattern noise gain of the selected pixel by means of the known calibration current to achieve pixel-level calibration, thereby Provides CMOS active pixel image sensor with not only high sensitivity but also improved fixed pattern noise compensation

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