设计了一种基于电容反馈跨阻放大器型(Capacitive Trans-impedance Amplifier, CTIA)像元电路与双Δ采样(Delta Double Sampling, DDS)的低照度CMOS图像传感器系统。采用CTIA像元电路提供稳定的光电二极管偏置电压以及高注入效率, 完成在低照度情况下对微弱信号的读取; 同时采用数字DDS结构, 通过在片外实现像元积分信号与复位信号的量化结果在数字域的减法, 达到抑制CMOS图像传感器中固定图案噪声的目的, 进一步提高低照度CIS的成像质量。基于0.35 μm标准CMOS工艺对此基于CTIA像元电路的CMOS图像传感器芯片进行流片, 像元阵列为256×256, 像元尺寸为16 μm×16 μm。测试结果表明该低照度CMOS图像传感器系统可探测到0.05 lx光照条件下的信号。

A low-light-level CMOS image sensor with Capacitive Trans-impedance Amplifier（CTIA） pixel circuit and Delta Double Sampling（DDS） was proposed. By using CTIA circuit, stable bias voltage of the photodiode and high injection ratio can be realized, and the weak signal in low-light-level condition can be readout; Meanwhile, an off-chip digital DDS was used to reduce the fixed pattern noise (FPN) which was realizing the subtraction algorithm between the reset signal and pixel signal after A/D conversion off-chip, and improve the image quality of the low-light-level CIS. This low-light-level CMOS image sensor (CIS) based on CTIA pixel circuit was implemented in the 0.35 μm standard CMOS technology. The pixel array was 256×256, and the pixel size was 16 μm×16 μm. The experimental results show that this low-light-level CIS can capture recognizable images with the illumination down to 0.05 lx.