Device and method for compensating dark current of image sensor

Abstract

The invention discloses a device and a method for compensating dark current of an image sensor. The device comprises a photosensitive pixel array, a dark pixel, a variable gain amplifier, an analog to digital converter and a unit gain buffer. The device is of a fully differential variable gain amplifier structure, two related double sampling capacitors are added, appropriate sequential control is used, difference between output voltage, after reset, of the photosensitive pixel and output voltage, after integration, of the photosensitive pixel is transmitted to an input end of the variable gain amplifier, and difference between output voltage, after reset, of the dark pixel and output voltage, after integration, of the dark pixel is transmitted to another input end of the variable gain amplifier. By sampling capacitors, feedback capacitors and appropriate sequential control, difference between photosensitive pixel reset integral signal difference and dark pixel composite integral signal difference is obtained, and the signals output are signals which are compensated by dark current and reflect actual light intensity information.

Description

technical field [0001] The invention belongs to the technical field of CMOS image sensors, and relates to an image sensor dark current compensation device and method. Background technique [0002] Image sensors are at the heart of modern electronic imaging systems, including video cameras, digital cameras, copiers, scanners, and more. Image sensors are mainly implemented based on two processes, complementary metal-oxide-semiconductor (CMOS) process and charge-coupled device (CCD) process. Due to its advantages of high integration, small size, and low power consumption, CMOS image sensor technology has achieved rapid development in recent years. However, the dark current of the CMOS image sensor is relatively large, especially when shooting a dark scene, a long exposure is required, the dark level generated by the dark current will occupy a large range of the signal, so that the output signal cannot reflect the real light intensity At the same time, because the dark level w...

AI Technical Summary

Problems solved by technology

In this implementation, before each frame of photo is read out, the loop of dark current compensation needs to be stabilized to generate a stable black level, and the stabilization time of the loop will vary with the gain of the variable gain amplifier. Therefore, this method of dark current compensation reduces the frame rate of the sensor

In addition, this closed-loop implementation requires a high-precision digital-to-analog converter, and its precision requirements are generally several bits higher than the analog-to-digital converter of the column readout circuit.

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