混合域实现图像块矩阵变换的CIS像素读出噪声分析

Pixel readout noise analysis of the CMOS image sensor with mixed-signal realizing block-matrix transform

为了研究双存储像素的读出噪声对混合域实现图像块矩阵变换的CMOS图像传感器(CIS)产生的误差影响,对其进行噪声分析。结合双存储像素的工作时序,对实现图像块矩阵变换过程中由于多次采样和双路存储而增加的kTC噪声、源跟随器的1/f噪声和热噪声进行分析并建立数学模型,总结出双存储像素读出噪声对一次块矩阵变换的误差影响。以二维离散余弦变换为例,通过CHRT 0.35 m标准CMOS工艺电路仿真并结合matlab/simulink对比验证,得出增大存储电容、减小源跟随器宽长比可以降低由于像素读出噪声引起的误差。结果证明,此方法可以有效降低噪声,指导电路设计。

In order to study the error caused by the dual-pixel’s readout noise in the CMOS Image Sensor with mixed-signal realizing block-matrix transform,the noise analysis is presented.With the timing of the dual-pixel,the mathematical model of kTC noise,source follower’s 1/f noise and thermal noise caused by multiple sampling and two signal paths storage is established and the formula of the error caused by the dual-pixel’s readout noise in one block-matrix transform is presented.Testing by circuit simulation with the CHRT 0.35 m standard CMOS process and comparing with Matlab/Simulink verification in two dimension discrete cosine transform（2D-DCT）,it is found that increasing the storage capacitor and reducing the W/L of source follower can reduce the error caused by the pixel readout noise.The results show that this method can effectively reduce pixel noise,guidance circuit design.