A Low kTC Noise and Low FPN Reset Method for Pixel in ToF Image Sensor

In this paper, a 256 x 128 rolling shutter time of flight (ToF) CMOS image sensor (CIS) with a lowkTC noise and low fixed pattern noise (FPN) reset method is presented. The pixel adopting the proposed reset method has two taps and three reset transistors. The two taps enable this ToF image sensor to capture depth image quickly and the three reset transistors ensure reduction of the kTC noise and FPN. This kind of ToF image sensor is implemented in a 0.13 mu m onepoly four-metal CMOS technology. The physical size of the pixel with the proposed reset method is 10 mu m x 10 mu m with a maximum fill factor of 69%. The chip size of the sensor is 4671 mu m x 3406 mu m. Measurement results show that the proposed reset method for ToF pixel can reduce the kTC noise and FPN at room temperature effectively. Themaximum reduction of kTC noise is 394.9 mu V. The maximum reduction of FPN is 531.8 mu V. Therefore, ToF sensors with the proposed reset method can achieve low thermal noise and high spatial uniformity.