Image sensor readout circuit and method for correcting dark current

Abstract

The invention discloses an image sensor readout circuit for correcting dark current, which includes an amplifier, a comparator and a counter, wherein one of the input ends of the amplifier is connected to the output end of the pixel unit through a sampling capacitor C1, and the sampling One end of the capacitor is connected to the output end of the pixel unit, and the other end is simultaneously connected to the input end of the amplifier, the amplification capacitor C2 and one end of the amplification capacitor Cf, the other end of the amplification capacitor C2 is connected to the output end of the amplifier, and the amplification capacitor The other end of Cf is connected to the dark current correction unit. The present invention provides an image sensor readout circuit for correcting dark current. The circuit of the present invention adds a feedback branch composed of a dark current correction unit, which realizes dark correction in the analog domain and before signal amplification, avoiding The traditional CIS has the problem of insufficient dynamic range at high temperature caused by dark correction in the digital domain.

Description

Technical field [0001] The present invention relates to the field of image sensor readout circuitry, and more particularly to an image sensor readout circuit and method for correcting dark currents. Background technique [0002] The dark current noise severely affects the image quality of CIS (CMOS image sensor), the impact of dark current noise on the quality of CIS imaging is mainly reflected in two aspects, and the non-uniformity of dark current is an important source of CIS fixed mode noise. Make the permeability of CIS to be deteriorated; Second, dark current will raise the data average of the entire image, especially under high temperature conditions, the dark current will significantly increase, if the traditional digital domain dark correction will make dark The current signal cannot be effectively reduced, and the dynamic range of the image will be greatly reduced, and the image quality is seriously affected. [0003] Due to the traditional CIS, the dark current correcti...

AI Technical Summary

Problems solved by technology

However, when the temperature is gradually higher, the dark current of the pixel increases very fast. At high temperature (for example, 90°C), the proportion of dark current signal may reach 40% (the specific percentage depends on the process). If the amplifier OP is amplified again, it will make The difference between VRST-VSIG is far beyond the range of the readout circuit (such as Image 6 In VSIG_X), in this case, the readout circuit cannot quantize the pixel signal normally

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