Abstract
This paper presents a new structure and method of range calculation for CMOS time-of-flight (TOF) range image sensors using pinned photodiodes. In the proposed method, a LED light with short pulse width and small duty ratio irradiates the objects and a back-reflected light is received by the TOF range imager. In TOF range image sensors, high speed charge transfer from the light receiving part to a charge accumulator is essential. It was found that the fastest charge transfer can be realized when the lateral electric field along the axis of charge transfer is constant and this condition is met when the shape of the diode exactly follows the relationship between the fully-depleted potential and the photodiode width. A TOF range imager prototype is designed and implemented with 0.18um CMOS image sensor technology for pinned photodiode 4T pixels. In the prototype, the response of the pixel output as a function of the light pulse delay has been measured.
