| CPC G01S 7/4865 (2013.01) [G01S 17/10 (2013.01); G01S 17/89 (2013.01)] | 22 Claims |
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1. A method comprising:
receiving a first plurality of digital codes from a time-to-digital converter (TDC), wherein the TDC has an input coupled to a first single photon avalanche diode (SPAD);
generating a coarse histogram from the first plurality of digital codes, the coarse histogram comprising a plurality of coarse bins that collectively correspond to a coarse histogram depth range from a lowest coarse histogram depth to a highest coarse histogram depth, wherein generating the coarse histogram comprises:
generating a first coarse histogram comprising a first plurality of bins from a first portion of the first plurality of digital codes based on a first clock,
generating a second coarse histogram comprising a second plurality of bins from a second portion of the first plurality of digital codes based on an offset first clock, wherein a length of a first depth range of the first coarse histogram is equal to a length of a second depth range of the second coarse histogram, the first depth range overlaps the second depth range, and the first coarse histogram has a same number of bins as the second coarse histogram, and
combining the first and second coarse histograms to generate the coarse histogram, wherein the generated coarse histogram has a higher depth resolution than each of the first and second coarse histograms;
detecting a peak coarse bin from the plurality of coarse bins, wherein the peak coarse bin corresponds to a peak coarse bin depth range from a lowest coarse peak depth to a highest coarse peak depth;
after receiving the first plurality of digital codes, receiving a second plurality of digital codes from the TDC;
generating a fine histogram from the second plurality of digital codes based on the detected peak coarse bin, the fine histogram comprising a plurality of fine bins that collectively correspond to a fine histogram depth range from a lowest fine histogram depth to a highest fine histogram depth, wherein the fine histogram depth range is narrower than the coarse histogram depth range, and wherein the lowest fine histogram depth is lower or equal to than the lowest coarse peak depth, and wherein or the highest fine histogram depth is higher or equal to than the highest coarse peak depth;
during a first time period, reading out the fine histogram associated with signals received from a first plurality of SPADs, and, simultaneously with the reading out the fine histogram associated with signals received from the first plurality of SPADs, performing the steps of receiving the first plurality of digital codes, generating the coarse histogram, detecting the peak coarse bin, receiving the second plurality of digital codes, and generating the fine histogram based on the detected peak coarse bin for signals received from a second plurality of SPADs different from the first plurality of SPADs; and
during a second time period different from the first time period, reading out the fine histogram associated with signals received from the second plurality of SPADs, and, simultaneously with the reading out the fine histogram associated with signals received from the second plurality of SPADs, performing the steps of receiving the first plurality of digital codes, generating the coarse histogram, receiving the second plurality of digital codes detecting the peak coarse bin, and generating the fine histogram for signals received from the first plurality of SPADs.
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