A CMOS Image Sensor Based on Uni fied Pixel Architecture With Time-Division Multiplexing Scheme for Color and Depth

Abstract

We propose a CMOS image sensor with time-divi sion multiplexing pixel architecture using standard pinned-photodiode for capturing 2-D color image as well as extracting 3-D depth in- formation of a target object. The proposed pixe l can alternately provide both color and depth images in each frame. Two split pho- todiode and four transfer gates in each pixel improve the transfer speed of generated electrons to be capable o f demodulating a high- frequency time-of- flight signal. In addition, four-shared pixel ar- chitecture acquires a color image with high spatial resolution and generates a reliable depth map by inhe rent binning operation in charge domain. A 712 496 pixel array has been fabricated using a0 . 1 1 - m standard CMOS imaging pr ocess and fully character- ized. A 6- m pixel with 34.5% apertur er a t i oc a nb eo p e r a t e da t 10-MHz modulation frequency with 70% demodulation contrast. We have successfully captured both images of exactly same scene from the fabricated test chip. It shows a depth uncertainty of less than 60 mm and a linearity error of about 2% between 1 and 3 m distance with 50-ms integration time. Moreover, high-gain readout operation enables to impro ve the performance , achieving about 43-mm depth uncertainty at 3 m.