CMOS-compatible three-dimensional image sensor IC

A CMOS-implementable integrated circuit (IC) time of flight (TOF) measurement system used with a generator that outputs light pulses commencing at time t0 to determine distance Z within resolution ΔZ between said IC and a target less than about 100 m distant, the IC including:

• an array comprising a plurality of pixel detectors to detect generated light pulse energy returned from said target, each of said pixel detectors having a pixel integration delay time exceeding 2·ΔZ/C, where C is speed of light, said array further comprising for each of said pixel detectors an associated pixel time interval counter;
• a system clock providing countable clock pulses to each said pixel time interval counter, said clock having a frequency at least about C/(2·ΔZ);
• logic to enable each said pixel time interval counter to count said clock pulses commencing with start of a generated light pulse at said time t0, and to disable each said pixel time interval counter from further counting clock pulses when an associated pixel detector detects energy from the generated said light pulse;
• wherein detection time for each said pixel detector includes actual time of flight (TOF) from said generator to said target to said pixel detector, as well as pixel integration delay time for said pixel detector;
• and
• wherein said pixel integration delay time may be removed on a per pixel detector basis to obtain said actual TOF such that a direct digital measurement proportional to said distance Z is obtained.

A method to determine distance Z between a detector array and a target less than about 100 m distant, the method comprising the following steps:

• (a) disposing said array so as to detect optical energy reflected from said target, the array comprising a plurality of pixel detectors, and for each pixel detector providing an associated charge collector, and for each pixel detector an associated shutter disposed intermediate an associated said pixel detector and associated said charge collector to control ability of said charge collector to collect charge output by an associated said pixel detector;
• (b) at time t0, illuminating said target with a first pulse of optical energy having pulse width PW and opening each said shutter to permit said collector to collect any output resulting from detected optical energy reflected from said target resulting from said pulse;
• (c) beginning at said time t0 to accumulate in each said collector any charge output by an associated said pixel detector;
• (d) at a time Tep, corresponding to approximately PW=Tep−t0, closing each said shutter to disable each said associated collector from accumulating further charge;
• (e) after said time Tep, evaluating charge associated in each said collector to obtain a measure of actual time of flight (TOF) for each said pixel detector to said target;
• and
• (f) at a subsequent time outputting a second pulse of known PW and opening and retaining open each said shutter until cessation of detected energy from said second pulse;
• wherein said distance Z to said target may be determined.

A CMOS-implementable integrated circuit (IC) time of flight (TOF) measurement system used with a generator outputting at least a first light pulse of pulse width PW to determine distance Z between said IC and a target less than about 100 m distant, the IC comprising:

• an array of pixel detectors to detect generated light pulse energy returned from said target, each pixel detector having a pixel integration delay time exceeding 2·ΔZ/C where C is speed of light;
• for each of said pixel detectors, an associated charge collector, and for each pixel detector an associated shutter disposed intermediate an associated said pixel detector and associated said charge collector to control ability of said charge collector to collect charge output by an associated said pixel detector;
• logic that opens each said shutter at a time t0 representing start of a generated said first light pulse to permit said collector to collect any output resulting from detected optical energy reflected from said target resulting from said first pulse, said logic closing each said shutter at a time Tep corresponding to approximately PW=Tep−t0 width of each said first pulse to disable each said associated collector from accumulating further charge;
• means for evaluating accumulated charge after said time Tep accumulated in each said collector to obtain a measure of actual time of flight (TOF) for each said pixel detector to said target;
• said logic further opening and retaining open each said shutter, at a subsequent time corresponding to output duration of a second pulse of known pulse width, until cessation of detected energy from said second pulse;
• wherein said distance Z to said target may be determined.