用于数字图像传感器的脉冲宽度调制读出方法研究

摘要

为提高数字像素图像传感器的动态范围，提出了一种具有自适应参考电压的脉冲宽度调制读出方法。该方法将像素阵列分成包含相同数目像素的像素块，通过参考电压产生模块使每个像素块的参考电压和像素块内光照强度相关，理论上这种结构能够将数字像素图像传感器的动态范围从48 dB提升至96 dB，实际仿真结果为88.16 dB。分析了像素分块内主要的噪声来源和参考电压产生模块的采样电容引入的偏差。采用65 nm CMOS工艺实现了4×4的像素块电路，在高光强和弱光强条件下分别将电路输出同理论计算值相比较，并分析了产生误差的原因。%A pulse width modulation( PWM)readout method,with self-adaptive reference voltage is introduced to enlarge dynamic range of digital image sensor. The pixel array is divided into blocks with the same pixel numbers, and each block generates its reference voltage through the voltage generator,which makes it related to illumination intensity within the block. It can double the dynamic range from 48 dB of typical PWM digital image sensors to 96 dB in theory,and the simulation shows it can achieve dynamic range of 88. 16 dB. Main noise sources within the pixel block and the deviation brought in by sampling capacitance are studied. A pixel block circuit of 4 ×4 is achieved by 65 nm CMOS process. Comparison of outputs and theory values are made under high and low luminance,and the reason which cause errors is analyzed.