Photoelectric conversion device and optical detection system
A photoelectric conversion device includes a plurality of pixels each including a photoelectric conversion unit configured to output a signal based on incidence of a photon, the photoelectric conversion unit including an avalanche photodiode configured to multiply a charge resulting from the incidence of the photon by avalanche multiplication, a processing circuit configured to process the signal output from the photoelectric conversion unit, and a pixel output circuit configured to control output of a signal processed by the processing circuit; a data line connected to the plurality of pixels; and a reception circuit configured to receive a pixel signal output from the plurality of pixels via the data line. An off-leakage current of a transistor constituting the reception circuit is lower than that of a transistor constituting the pixel output circuit.
1 . A photoelectric conversion device comprising:
a plurality of pixels each including
a photoelectric conversion unit configured to output a signal based on incidence of a photon, the photoelectric conversion unit including an avalanche photodiode configured to multiply a charge resulting from the incidence of the photon by avalanche multiplication,
a counter configured to count the signal output from the photoelectric conversion unit, and
a pixel output circuit configured to control output of a count counted by the counter;
a data line connected to the plurality of pixels; and
a reception circuit configured to receive a pixel signal output from the plurality of pixels via the data line,
wherein an off-leakage current of a first transistor constituting the reception circuit is lower than that of a second transistor constituting the pixel output circuit,
wherein the photoelectric conversion device is configured to record time information about when the count of the counter reaches a predetermined value, and
wherein the photoelectric conversion device further comprises an acquisition unit configured to acquire a predicted count based on the time information.
2 . The photoelectric conversion device according to claim 1 , wherein a threshold voltage of the first transistor has an absolute value greater than that of a threshold voltage of the second transistor.
3 . The photoelectric conversion device according to claim 1 , wherein an off-leakage current of a third transistor constituting the counter is lower than that of the second transistor constituting the pixel output circuit.
4 . The photoelectric conversion device according to claim 3 , wherein a threshold voltage of the third transistor has an absolute value greater than that of a threshold voltage of the second transistor.
5 . The photoelectric conversion device according to claim 1 , wherein the pixel output circuit is an open-drain buffer circuit.
6 . The photoelectric conversion device according to claim 5 , wherein each of the first and second transistors constitutes a part of an electrical path extending from a power supply voltage node to a reference voltage node via the data line.
7 . The photoelectric conversion device according to claim 5 , wherein the data line includes a pair of signal lines configured to output a non-inverted signal and an inverted signal of the pixel signal.
8 . The photoelectric conversion device according to claim 1 , wherein the pixel output circuit is a buffer circuit.
9 . The photoelectric conversion device according to claim 1 , wherein the first transistor has a gate width greater than that of the second transistor.
10 . The photoelectric conversion device according to claim 1 , wherein the reception circuit includes a reset circuit configured to reset a voltage of the data line.
11 . The photoelectric conversion device according to claim 1 , wherein the reception circuit includes a determination circuit configured to determine a signal level of the data line.
12 . The photoelectric conversion device according to claim 1 , wherein the pixel output circuit is configured to, if the count reaches the predetermined value, control output of the time information.
13 . The photoelectric conversion device according to claim 1 , further comprising a first substrate where the avalanche diode is disposed and a second substrate where the counter, the pixel output circuit, and the reception circuit are disposed, the first and second substrates being stacked on each other.
14 . An optical detection system comprising:
the photoelectric conversion device according to claim 1 ; and
a signal processing apparatus configured to process a signal output from the photoelectric conversion device.
15 . The optical detection system according to claim 14 , wherein the signal processing apparatus is configured to generate a distance image indicating distance information about an object based on the signal.
16 . A moving body comprising:
the photoelectric conversion device according to claim 1 ;
a distance information acquisition unit configured to acquire distance information about an object from a parallax image based on a signal output from the photoelectric conversion device; and
a control unit configured to control the moving body based on the distance information.
17 . An optical detection system comprising:
a photoelectric conversion device comprising a plurality of pixels each including
a photoelectric conversion unit configured to output a signal based on incidence of a photon, the photoelectric conversion unit including an avalanche photodiode configured to multiply a charge resulting from the incidence of the photon by avalanche multiplication,
a counter configured to count the signal output from the photoelectric conversion unit, and
a pixel output circuit configured to control output of a count counted by the counter;
a data line connected to the plurality of pixels; and
a reception circuit configured to receive a pixel signal output from the plurality of pixels via the data line,
wherein an off-leakage current of a first transistor constituting the reception circuit is lower than that of a second transistor constituting the pixel output circuit,
wherein the photoelectric conversion device is configured to record time information about when the count of the counter reaches a predetermined value, and
wherein the optical detection system further includes an acquisition apparatus configured to acquire a predicted count based on the time information.