Time-of-flight closest target ranging with pulse distortion immunity

A method of operating a time-of-flight (ToF) ranging system, the method comprising:

• transmitting, by a light source of the ToF ranging system, light pulses toward one or more targets;
• receiving, by a ToF sensor of the ToF ranging system, the light pulses reflected by the one or more targets;
• generating a histogram based on the received light pulses;
• generating a differential histogram by computing differences between adjacent histogram bins of the histogram and assigning the computed differences as values of respective histogram bins of the differential histogram;
• finding a first histogram bin of the differential histogram, wherein a first value of the first histogram bin of the differential histogram is larger than a pre-determined threshold or is a maximum value of the values of the histogram bins of the differential histogram, wherein the first histogram bin is a leftmost histogram bin of the differential histogram that has the first value;
• and
• computing an estimate of a distance of a closest target by adding a pre-determined offset to a first distance of the first histogram bin, wherein the pre-determined offset is proportional to half of a width of a light pulse transmitted by the light source.

A time-of-flight (ToF) ranging system comprising:

• a light source configured to transmit light pulses for illuminating one or more targets;
• a ToF sensor configured to receive reflected light pulses from the one or more targets and to generate a histogram based on the reflected light pulses;
• a processor configured to determine a distance of a closest target of the one or more targets by:
• finding a first rising edge in the histogram that corresponds to a rising edge of a reflected light pulse reflected by the closest target, wherein finding the first rising edge comprises:
• computing differences between adjacent histogram bins of the histogram and assigning the computed differences as gradients of respective histogram bins of the histogram;
• and
• finding a first histogram bin of the histogram having a first value, wherein the first value is a maximum value of the computed differences, or is larger than a pre-determined threshold value, wherein the first histogram bin is a leftmost histogram bin of the histogram having the first value;
• and
• calculating an estimate of the distance of the closest target by adding a pre-determined offset to a distance of the first rising edge, wherein the pre-determined offset is proportional to half of a width of a transmitted light pulse.