Direct time of flight distance measuring system with in-pixel histogram circuit incorporating lfsr shift register based photon counting accumulator

Abstract

A novel and useful direct time of flight distance measuring device that incorporates smart pixel architecture, real-time in-pixel histogram and intensity acquisition, optical power control, and variable resolution. The device avoids the use of time to digital (TDC) converters by generating in-pixel histograms based on a global high-speed clock that implements per pixel time bin single photon event accumulation using circuitry located under or near the SPAD pixels. Laser events are processed within a smart pixel architecture increasing substantially the data conversion throughput while reducing data movement in the device to achieve high spatial resolution, low power operation, and fast reliable depth capture. The device uses a compact split pseudo-random counter. Each smart pixel operates independently and concurrently, allowing the sensor to operate in global shutter while monitoring the SNR and determining the optimal exposure time for transmitter and receiver power savings. This enables full control of the pixel operation, enable/disable, and optimization.