Global shutter pixel structure for increasing voltage amplitude of output signal and control method thereof

Abstract

The invention discloses a global shutter pixel structure for increasing voltage amplitude of an output signal. The global shutter pixel structure is characterized in that the electrical structure of a sampling switch is innovated, two sampling capacitors can be managed independently, and the magnitude of sampling capacitance is kept unchanged during charge conversion in a readout process. In addition, the invention further discloses a signal control method based on the structure. The global shutter pixel structure and the control method have the advantages that the voltage amplitude the output signal of the structure can be increased, dynamic range of pixels is expanded, gray quality of images is improved, and indicators, such as CVF, PLS and noise, of a typical 8T structure are unchanged.

Description

technical field [0001] The invention relates to a CMOS image sensor, in particular to a global shutter pixel structure and a control method capable of increasing output signal voltage amplitude. Background technique [0002] When shooting a high-speed moving object, it is necessary to use a global shutter to avoid image distortion; on the existing CMOS image sensor, the typical pixel structure used to realize the global shutter function is as follows: figure 1 As shown, the pixel structure is changed based on the traditional 4T pixel structure, which consists of a photodiode, a transmission tube, a reset switch, a source follower, a current source load, two sampling switches (M5 and M6), two sampling Composed of capacitors (C1 and C2), source follower 2 and row selection switch; its working principle is: 1) Drive the transfer tube and reset switch to close to reset the photodiode, and then disconnect the transfer tube and reset switch, the image Start the exposure; 2) A...

AI Technical Summary

Problems solved by technology

[0004] The principle of the present invention is: in the prior art, since the two sampling capacitors are only connected by one sampling switch, when the optical signal is read out, the optical signal charge is distributed in the two sampling capacitors at the same time, and finally the row selection switch outputs light The voltage amplitude of the signal will be reduced by C1·(V reset -V signal ) / (C1+C2), and after adopting the scheme of the present invention, the two sampling capacitors can be managed separately, and the size of the sampling capacitor remains unchanged during the charge conversion in the readout process, which solves the problem that the voltage amplitude of the output signal is reduced Problem; at the same time, the pixel can adopt correlated double sampling, which eliminates KTC noise; moreover, the storage environment of the reset voltage signal and the photovoltage signal is the same, and has a small PLS through correlated double sampling; compared with the typical 8T pixel structure, there is no reduced PLS , CVF, noise and other pointers

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