US-12618951-B2 - Light detection device, light detection method and optical distance sensor

US12618951B2US 12618951 B2US12618951 B2US 12618951B2US-12618951-B2

Abstract

A light detection device detects incident light acc ding to a detection start timing. The light detection device includes a plurality of photosensors, a signal combining circuit, a detection circuit, and at least one time measurement circuit. The plurality of photosensors receive light to generate output signals indicating light reception results, respectively. The signal combining circuit sums a plurality of output signals from the respective photosensors to generate a combined signal. The detection circuit detects a timing, at which the combined signal is maximized after the detection start timing, to generate a detection signal indicating the detected timing. The time measurement circuit measures a count period between the detection start timing and the detected timing based on the detection signal.

Inventors

Masanobu Horino
Yuki Matsui
Ken NAKAMURO
Sayuki Nakada

Assignees

OMRON CORPORATION

Dates

Publication Date: 20260505
Application Date: 20190308
Priority Date: 20180315

Claims (9)

1 . A light detection device for detecting incident light according to a detection start timing, the light detection device comprising: a plurality of photosensors configured to receive light to generate output signals indicating light reception results, respectively; a signal combining circuit configured to sum the plurality of output signals from the respective photosensors to generate a combined signal; a detection circuit configured to detect a maximum timing to generate a detection signal, based on the combined signal from the signal combining circuit, the maximum timing being a timing at which the combined signal is maximized after the detection start timing, the detection signal indicating the detected maximum timing as a time when the combined signal is maximized; and at least one time measurement circuit configured to measure a count period in response to detecting the maximum timing by the detection circuit, based on the detection signal input thereto from the detection circuit, the count period being defined from the detection start timing to the detected maximum timing by the detection circuit as the time when the combined signal is maximized.
2 . The light detection device according to claim 1 , wherein the photosensors are single photon avalanche photodiode each configured by an avalanche photodiode operated in a Geiger mode.
3 . The light detection device according to claim 1 , wherein the detection circuit comprises a maximum value holding circuit configured to generate a maximum value signal which is updated for each time the combined signal updates a maximum value.
4 . The light detection device according to claim 3 , wherein the detection circuit further comprises: a delay circuit configured to delay the maximum value signal by a predetermined delay period to generate a delay signal; and a comparison circuit configured to compare the maximum value signal and the delay signal with each other to output the detection signal, which indicates a timing at which the maximum value signal exceeds the delay signal.
5 . The light detection device according to claim 3 , wherein the detection circuit further comprises: a delay circuit configured to delay the combined signal by a predetermined delay period to generate a delay signal; and a comparison circuit configured to compare the maximum value signal and the delay signal with each other to output the detection signal, which indicates a timing at which the delay signal reaches the maximum value signal.
6 . The light detection device according to claim 1 , further comprising a statistical processor configured to acquires information, which indicates a last predetermined number of count periods in multiple count periods measured for one detection start timing, to perform statistical processing on the acquired information.
7 . The light detection device according to claim 6 , comprising a plurality of the time measurement circuits, and further comprising a selection circuit configured to switch in turn a time measurement circuit for measuring the count period among the plurality of time measurement circuits at each timing indicated by the detection signal.
8 . An optical distance sensor comprising: a light projector that projects light; and the light detection device according to claim 1 , wherein the time measurement circuit in the light detection device is configured to measure the count period using a timing at which the light projector projects light as the detection start timing.
9 . A light detection method by a light detection device comprising a plurality of photosensors for detecting incident light according to a detection start timing, the method including: receiving light at the plurality of photosensors to generate each of output signals indicating light reception results; and summing the plurality of output signals from the respective photosensors to generate a combined signal; detecting a maximum timing to generate a detection signal, based on the combined signal, the maximum timing being a timing at which the combined signal is maximized after the detection start timing, the detection signal indicating the detected maximum timing as a time when the combined signal is maximized; and measuring a count period in response to detecting the maximum timing, based on the detection signal, the count period being defined from the detection start timing to the detected timing as the time when the combined signal is maximized.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This is the U.S. national stage of application No. PCT/JP2019/009225, filed on Mar. 8, 2019. Priority under 35 U.S.C. § 119 (a) and 35 U.S.C. § 365 (b) is claimed from Japanese Application No. 2018-048001, filed Mar. 15, 2018, the disclosure of which is also incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a light detection device, a light detection method, and an optical distance sensor including the light detection device. BACKGROUND ART There is known an optical distance sensor that uses time of flight (TOF) of light. The optical distance sensor irradiates an object with light and detects the light reflected by the object, thereby measuring a distance corresponding to the time of fight of light traveling back and forth to the object. In the optical distance sensor, a technique using a single photon avalanche photodiode (SPAD) for light detection is proposed (e.g., Patent Documents 1 and 2). Patent Document 1 discloses a distance measurement device including a plurality of SPADs in a receiver unit. The distance measurement device of Patent Document 1 determines that a measurement pulse is detected when a summated signal indicating the sum of electrical pulses output from the plurality of SPAD crosses a predetermined threshold and a rising slope of the summated signal crosses a predetermined slope threshold. Patent Document 2 discloses a light detector including a plurality of SPADs in an optical distance measurement device. The light detector of Patent Document 2 sums rectangular pulses output from the plurality of SPADs, compares a summed output value with a predetermined reference value, and outputs a trigger signal according to a comparison result. CITATION LIST Patent Document Patent Document 1: US 2015/0177369 A1 Patent Document 2: JP 5644294 B SUMMARY Technical Problem The SPAD responds to even one photon, but the reaction is stochastic. Thus, the rise of the summed signal is steeper as the number of received photons increases, and gentler as the number of received photons decreases. Accordingly, the distance measurement device of Patent Document 1 or the like fails to detect light having a little number of photons with the slope threshold set larger, and erroneously detects disturbance light with the slope threshold set smaller. Thus, it is difficult to accurately perform light detection in the optical distance sensor in the related art. An object of the present disclosure is to provide a light detection device, a light detection method, and an optical distance sensor capable of accurately performing light detection in an optical distance sensor. Solution to Problem A light detection device according to the present disclosure detects incident light according to a detection start timing. The light detection device includes a plurality of photosensors, a signal combining circuit, a detection circuit, and at least one time measurement circuit. The plurality of photosensors receive light to generate output signals indicating light reception results, respectively. The signal combining circuit sums a plurality of output signals from the respective photosensors to generate a combined signal. The detection circuit detects a timing, at which the combined signal is maximized after the detection start timing, to generate a detection signal indicating the detected timing. The time measurement circuit measures a count period between the detection start timing and the detected timing based on the detection signal. A light detection method according to the present disclosure provides a method by which a light detection device detects incident light according to a detection start timing. An optical distance sensor according to the present disclosure includes a light projector that projects light, and a light detection device. The time measurement circuit in the light detection device measures the count period using a timing at which the light projector projects light as the detection start timing. Advantageous Effect With the light detection device, the light detection method, and the optical distance sensor according to the present disclosure, it is possible to accurately perform the light detection in the optical distance sensor. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for describing an application example of a light detection device according to the present disclosure. FIG. 2 is a block diagram illustrating a configuration of an optical distance sensor according to a first embodiment. FIG. 3 is a block diagram illustrating a configuration of a light detection device according to the first embodiment. FIG. 4 is a circuit diagram illustrating a configuration example of a maximum value holding circuit in the light detection device. FIGS. 5A to 5D are timing charts for describing a method of combining a combined signal in the light detection device. FIGS. 6A to 6D are timing charts illustrating an operation of the light detection