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

A method of time of flight distance measuring, comprising:

• detecting photons, using an array of pixel photon detectors, for detecting photons reflected off one or more targets in response to a series of laser events;
• in-pixel histogram circuit circuits disposed under said plurality of pixel photon detectors, each in-pixel histogram circuit incorporating an accumulator per discrete time bin, each accumulator including a linear feedback shift register (LFSR) circuit, wherein each LFSR circuit is divided into multiple LFSR circuits coupled by one or more carry bits;
• generating a histogram for each pixel or groups of pixels whereby photon detection counts are maintained for a plurality of discrete time bins over an exposure period with each time bin corresponding to a particular delay interval equivalent to distance;
• and simultaneously generating an intensity measurement for each individual pixel.

A time of flight distance measuring system, comprising:

• an array of laser emitters operative to generate and emit pulses of laser light as a series of laser events that illuminate an area;
• an array of pixel photon detectors for detecting photons reflected off one or more targets in response to the series of laser events;
• in-pixel histogram circuits disposed under said plurality of pixel photon detectors, each in-pixel histogram circuit incorporating an accumulator per discrete time bin for counting photons, each accumulator including a linear feedback shift register (LFSR) circuit, wherein each LFSR circuit is divided into multiple LFSR circuits coupled by one or more carry bits, said in-pixel histogram circuit operative to:
• generate a histogram for each macropixel whereby photon detection counts are maintained for a plurality of discrete time bins over an exposure period with each time bin corresponding to a particular delay interval equivalent to distance;
• and
• simultaneously generate an intensity measurement for each individual pixel.