US-12625271-B2 - Ranging device

US12625271B2US 12625271 B2US12625271 B2US 12625271B2US-12625271-B2

Abstract

A ranging device includes: a frequency distribution generation unit that generates a frequency distribution of a light reception count value counted in each bin period; a frequency distribution holding unit that holds the frequency distribution generated by the frequency distribution generation unit; and a phase setting unit that sets a phase of start timings of the bin periods with respect to periodic light emission timings to an object. In a case where a first frequency distribution acquired by a first phase in a first period is held in the frequency distribution holding unit, and then a second frequency distribution acquired by a second phase in a second period next to the first period is held in the frequency distribution holding unit, at least a part of the first frequency distribution is erased from the frequency distribution holding unit until the holding of the second frequency distribution is completed.

Inventors

Yasuyo Sakamoto
Masashi Niwa

Assignees

CANON KABUSHIKI KAISHA

Dates

Publication Date: 20260512
Application Date: 20230713
Priority Date: 20220725

Claims (13)

1 . A ranging device comprising: a time counting unit configured to perform time counting; a light receiving unit configured to generate a pulse based on light including reflected light from an object and counts the pulse to acquire a light reception count value; a frequency distribution generation unit configured to generate a frequency distribution of the light reception count value counted in each of a plurality of bin periods in the time counting; a frequency distribution holding unit configured to hold the frequency distribution generated by the frequency distribution generation unit; a phase setting unit configured to set a phase of start timings of the plurality of bin periods with respect to periodic light emission timings to the object; a holding information control unit configured to control holding of information in the frequency distribution holding unit; and an output unit configured to output distance information, wherein in a case where a first frequency distribution acquired by a first phase in a first period is held in the frequency distribution holding unit, and then a second frequency distribution acquired by a second phase different from the first phase in a second period next to the first period is held in the frequency distribution holding unit, the holding information control unit controls the frequency distribution holding unit so that at least a part of the first frequency distribution is erased from the frequency distribution holding unit before the holding of the second frequency distribution is completed, and wherein the output unit holds a part of the first frequency distribution before the first frequency distribution is erased.
2 . The ranging device according to claim 1 , wherein the holding information control unit erases all of the first frequency distribution from the frequency distribution holding unit after the first frequency distribution is held and before the holding of the second frequency distribution is completed.
3 . The ranging device according to claim 1 , wherein the first frequency distribution and the second frequency distribution are held in the same storage area in the frequency distribution holding unit.
4 . The ranging device according to claim 1 further comprising: a light emitting unit configured to emit light to the object; and a control unit configured to synchronously control a light emission timing of the light emitting unit and a timing at which the time counting unit starts counting.
5 . The ranging device according to claim 1 , wherein the output unit outputs the distance information based on a third frequency distribution obtained by compositing the part of the first frequency distribution held in the output unit and a part of the second frequency distribution.
6 . The ranging device according to claim 5 , wherein the part of the first frequency distribution includes a bin period in which the light reception count value is largest in the first frequency distribution.
7 . The ranging device according to claim 6 , wherein the part of the second frequency distribution includes a plurality of bin periods corresponding to a bin period in which the light reception count value is largest in the first frequency distribution.
8 . The ranging device according to claim 5 , wherein the output unit generates the third frequency distribution by compositing a frequency distribution of a predetermined number of bin periods selected from the first frequency distribution in descending order of the number of light reception count values and a frequency distribution of a predetermined number of bin periods selected from the second frequency distribution in descending order of the number of light reception count values.
9 . The ranging device according to claim 5 , wherein the output unit extracts and outputs the distance information from a bin period in which the light reception count value is largest in the third frequency distribution.
10 . The ranging device according to claim 1 , wherein each of the first frequency distribution and the second frequency distribution includes a light reception count value counted in a first bin period and a light reception count value counted in a second bin period having a longer time interval than the first bin period.
11 . The ranging device according to claim 10 , wherein a distance corresponding to the second bin period is greater than a distance corresponding to the first bin period.
12 . A photodetection system comprising: the ranging device according to claim 1 ; and a signal processing unit configured to process a signal output from the ranging device.
13 . A movable body comprising: the ranging device according to claim 1 ; and a movable body control unit configured to control the movable body based on distance information acquired by the ranging device.

Description

BACKGROUND OF THE INVENTION Field of the Invention The present disclosure relates to a ranging device. Description of the Related Art Japanese Patent Application Laid-Open No. 2020-190419 discloses a ranging device that measures a distance to an object based on a time difference between a time at which light is irradiated and a time at which reflected light is received. The ranging device of Japanese Patent Application Laid-Open No. 2020-190419 calculates a distance from a frequency distribution of a count value of incident light with respect to time from light emission. Japanese Patent Application Laid-Open No. 2020-190419 discloses a method of measuring a distance to an object by making the phase of acquisition time of the frequency distribution different for each of a plurality of sub-pixels and superimposing the frequency distributions of the count values acquired by the plurality of sub-pixels. Japanese Patent Application Laid-Open No. 2019-215260 discloses a method of calculating accuracy of ranging by acquiring a plurality of signals with different phases of acquisition times of signals in a ranging device. In order to store a plurality of frequency distributions, a large amount of storage capacity is required. Therefore, in a method of using signals acquired with different phases as described in Japanese Patent Application Laid-Open No. 2020-190419 and Japanese Patent Application Laid-Open No. 2019-215260, it may be a problem to reduce the storage capacity required for holding the frequency distribution while maintaining the ranging accuracy such as spatial resolution in the light receiving surface. SUMMARY OF THE INVENTION It is an object of the present disclosure to provide a ranging device in which a storage capacity required for holding a frequency distribution is reduced while maintaining ranging accuracy. According to a disclosure of the present specification, there is provided a ranging device including: a time counting unit configured to perform time counting; a light receiving unit configured to generate a pulse based on light including reflected light from an object and counts the pulse to acquire a light reception count value; a frequency distribution generation unit configured to generate a frequency distribution of the light reception count value counted in each of a plurality of bin periods in the time counting; a frequency distribution holding unit configured to hold the frequency distribution generated by the frequency distribution generation unit; a phase setting unit configured to set a phase of start timings of the plurality of bin periods with respect to periodic light emission timings to the object; and a holding information control unit configured to control holding of information in the frequency distribution holding unit. In a case where a first frequency distribution acquired by a first phase in a first period is held in the frequency distribution holding unit, and then a second frequency distribution acquired by a second phase different from the first phase in a second period next to the first period is held in the frequency distribution holding unit, the holding information control unit controls the frequency distribution holding unit so that at least a part of the first frequency distribution is erased from the frequency distribution holding unit until the holding of the second frequency distribution is completed. Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a schematic configuration example of a ranging device according to a first embodiment. FIG. 2 is a diagram illustrating an outline of an operation of the ranging device in one ranging period according to the first embodiment. FIGS. 3A, 3B, 3C, and 3D are histograms visually illustrating frequency distributions of pulse count values according to the first embodiment. FIGS. 4A and 4B are histograms illustrating examples of frequency distributions acquired in the first embodiment. FIGS. 5A, 5B, and 5C are histograms illustrating an example of compositing of frequency distributions acquired in the first embodiment. FIG. 6 is a flowchart illustrating an operation of the ranging device according to the first embodiment. FIG. 7 is a block diagram illustrating a schematic configuration example of a ranging device according to a second embodiment. FIGS. 8A, 8B, 8C, 8D, and 8E are histograms illustrating examples of frequency distributions acquired in the second embodiment. FIG. 9 is a schematic view illustrating the overall configuration of a photoelectric conversion device according to a third embodiment. FIG. 10 is a schematic block diagram illustrating a configuration example of a sensor substrate according to the third embodiment. FIG. 11 is a schematic block diagram illustrating a configuration example of a circuit substrate according to