Distance measurement device
A distance measurement device includes a light source; an optical system configured to emit emission light from the light source and to receive reflected light of the emission light; a plurality of pixels configured to detect the received reflected light, each including at least one sensor, and arranged in a pixel area on a substrate; and a control circuit. The control circuit is configured to: identify first reflected light detected in a first pixel in association with first emission light; and measure a distance based on a time difference between the first emission light and the identified first reflected light. The first emission light includes a first, second, and third pulse in succession. A first interval between the first and second pulse differs from a second interval between the second and third pulse.
1 . A distance measurement device comprising:
a light source;
an optical system configured to emit emission light from the light source and to receive reflected light of the emission light;
a plurality of pixels configured to detect the received reflected light, each including at least one sensor, and arranged in a pixel area on a substrate; and
a control circuit, wherein
the control circuit is configured to:
identify first reflected light detected in a first pixel in association with first emission light; and
measure a distance based on a time difference between the first emission light and the identified first reflected light,
the first emission light includes a first pulse, second pulse, and third pulse in succession,
a first interval between the first pulse and the second pulse differs from a second interval between the second pulse and the third pulse,
the first reflected light corresponds to at least two of the first pulse, the second pulse, and the third pulse,
the control circuit is configured to:
detect a first peak candidate in which the first reflected light becomes maximum;
further detect a second peak candidate in which the first reflected light becomes maximum in the vicinity of a time corresponding to the first peak candidate; and
identify the first reflected light based on the first peak candidate and the second peak candidate,
the control circuit includes a finite impulse response (FIR) filter, and is configured to detect the first peak candidate and the second peak candidate by the FIR filter, and
a sampling interval of the FIR filter is equal to shorter a one of the first interval and the second interval.
2 . The distance measurement device according to claim 1 , wherein
the control circuit is configured to further detect the second peak candidate in a range from a time corresponding to the first peak candidate to a sum of the first interval and the second interval.
3 . The distance measurement device according to claim 1 , wherein
a brightness of the second peak candidate is lower than a brightness of the first peak candidate.
4 . The distance measurement device according to claim 1 , wherein
the control circuit is configured to identify the first reflected light based on second reflected light detected in a second pixel adjacent to the first pixel.
5 . The distance measurement device according to claim 1 , wherein
the second interval is double the first interval.
6 . The distance measurement device according to claim 1 , wherein
the first pulse, the second pulse, and the third pulse have the same brightness and the same pulse width.
7 . The distance measurement device according to claim 6 , wherein
the first interval and the second interval are longer than a sum of the pulse width and a time constant of a recovery response of the first pixel.
8 . The distance measurement device according to claim 1 , wherein
the first interval and the second interval are longer than a time-converted distance measurement accuracy of the measured distance.
9 . The distance measurement device according to claim 1 , wherein
the control circuit is configured to measure the distance based on, when a brightness of the first reflected light is equal to or greater than a first threshold, a difference between a first time at which the first pulse of the first emission light rises and a second time at which the brightness of the first reflected light exceeds a second threshold which is smaller than the first threshold.
10 . The distance measurement device according to claim 1 , wherein
the control circuit is configured to measure the distance based on, when a brightness of the first reflected light is equal to or greater than a first threshold, a difference between a third time and a fourth time, the third time being between when the first pulse of the first emission light rises and when the third pulse falls, the fourth time being between when the brightness of the first reflected light exceeds a second threshold and when the brightness becomes lower than the second threshold, the second threshold being smaller than the first threshold.
11 . The distance measurement device according to claim 1 , wherein
the at least one sensor includes an avalanche photodiode whose anode is coupled to a first power supply node, and a quench element whose first end is coupled to a second power supply node and second end is coupled to a cathode of the avalanche photodiode, and
the control circuit applies a first voltage to the first power supply node and a second voltage higher than the first voltage to the second power supply node while turning the sensor on.