Photon detecting 3D imaging sensor device
A photon detecting 3D imaging sensor device for detecting a distance information for pixels in an image includes an array of detector units. Each detector unit is configured to receive a light signal pulse and to provide a detection signal pulse on receipt of the light signal pulse. The 3D imaging device further includes a pulse selection unit including a decision tree with one or more stages. Each of the stages has one or more decision makers which are cascaded to propagate the earliest detection signal pulse of one of a respective detector unit as a timing signal. The 3D imaging device further includes a time-to-digital converter configured to receive the timing signal and to provide a time stamp depending on the timing signal. The time stamp indicates the distance information for a pixel of the image.
1. A photon detecting 3D imaging sensor device for detecting distance information for pixels in an image, comprising:
an array of detector units, wherein each of the detector units is configured to receive a respective light signal pulse and to provide a respective detection signal pulse on receipt of the respective light signal pulse;
a pulse selection unit including a decision tree with a plurality of stages, wherein each of at least a subset of the plurality of stages has a plurality of decision makers which are cascaded to propagate an earliest detection signal pulse of a respective one of the detector units as a timing signal;
a time-to-digital converter configured to receive the timing signal and to provide a time stamp depending on the timing signal wherein the time stamp indicates a distance information for a respective one of the pixels in the image;
an address determining unit; wherein:
each of the plurality of decision makers is configured to provide an address information indicating which of the detection signal pulses is the respective earliest detection signal pulse;
the address determining unit is configured to generate an address write signal indicating the one detector unit which has provided the earliest detection signal pulse depending on the respective address information of each of the decision makers; and
the address determining unit has one or more multiplexer trees each for generation of a respective bit of the address write signal, wherein each of the multiplexer trees is configured so that each multiplexer in the respective multiplex tree receives at its inputs address information of decision makers of one of the stages of the pulse selection unit or outputs of multiplexers of a preceding stage of the respective multiplexer tree and at its control input the address information of one of the decision makers of a subsequent one of the stages of the pulse selection unit.
2. The 3D imaging sensor device according to claim 1 , wherein the decision makers of the decision tree are each configured to select from each of two or more of the detection signal pulses the one of the two or more of the detection signal pulses which has been received earliest and to apply the respective earliest detection signal pulses on a decision maker output.
3. The 3D imaging sensor device according to claim 2 , wherein the decision maker outputs of two of the decision makers of one of the stages are coupled with inputs of a further one of the decision makers of a next one of the stages.
4. The 3D imaging sensor device according to claim 1 , wherein at least one of the decision makers includes two coupled flipflops each of which is configured to be triggered by one of the detection signal pulses and to block the respective other of the flipflops being triggered by the other of the detection signal pulses, wherein an output of the triggered flipflop is applied on the decision maker output.
5. The 3D imaging sensor device according to claim 4 , wherein the outputs of the respective flipflops are stored in a latch which provides an address information indicating which of the detection signal pulses has been the earliest detection signal pulse.
6. The 3D imaging sensor device according to claim 1 , wherein photodiodes are arranged in an array of photodiodes so that a single light signal pulse reflected on an object is capable of interacting with a plurality of the photodiodes of the array of photodiodes.
7. The 3D imaging sensor device according to claim 6 , wherein the photodiodes include one or more single-photon avalanche diodes.
8. The 3D imaging sensor device according to claim 7 , wherein the detector units are each associated to one of a plurality of single-photon avalanche diodes of the array of photodiodes, wherein each detector unit is configured to quench the associated single-photon avalanche diode after receipt of a light signal pulse.
9. The 3D imaging sensor device according to claim 1 , wherein the time-to-digital converter is configured to continuously run, wherein the time stamp indicates a counter value depending on the timing signal.