Distance measurement device, distance measurement method, and non-transitory computer-readable storage medium

Patent metadata

Field	Value
Publication number	US-2022018937-A1
Application number	US-202117307425-A
Country	US
Kind code	A1
Filing date	May 4, 2021
Priority date	Jul 15, 2020
Publication date	Jan 20, 2022
Grant date	—

Abstract

A distance measurement device includes the plurality of laser sensors and a processor. The plurality of laser sensors configured to project a laser beam and receive reflected light from a measurement target that moves within a measurement region. The processor configured to drive, based on the measurement region and a provision position of the plurality of laser sensors, each of the laser sensors at a light emission cycle in which a light receiving window that receives reflected light of own light and an interference risk range are included the interference risk range being a range in which an interference is caused by a laser beam from another laser sensor. The processor controls to laser beam emission timings of the plurality of laser sensors so as to be different from each other.

First claim

What is claimed is:

1 . A distance measurement device comprising:
a plurality of laser sensors configured to project a laser beam and receive reflected light from a measurement target that moves within a measurement region; and a processor configured to drive, based on the measurement region and a provision position of the plurality of laser sensors, each of the laser sensors at a light emission cycle in which a light receiving window that receives reflected light of own light and an interference risk range are included the interference risk range being a range in which an interference is caused by a laser beam from another laser sensor, wherein the processor controls to laser beam emission timings of the plurality of laser sensors so as to be different from each other.

2 . The distance measurement device according to claim 1 , wherein
the processor controls to the laser beam emission timings being deviated by light emission delay times different from each other with respect to a laser sensor to be a reference.

3 . The distance measurement device according to claim 1 , wherein
the processor is further configured to: define the measurement region by an XYZ coordinate system, obtain a minimum value d 1 of a point P 1 (x1, y1, z1) closest to a provision position S (x0, y0, z0) of a single laser sensor among points in the measurement region from a formula which is d 1 ={(x1−x0) 2 +(y1−y0) 2 +(z1−z0) 2 } 1/2 , obtain a minimum flight time t 1 of the laser beam from the minimum value d 1 from a formula which is t 1 =(d 1 /c)×2, c indicate a speed of light, obtain a maximum value d 2 of a point P 2 (x2, y2, z2) farthest from the provision position S (x0, y0, z0) among the points in the measurement region from a formula which is d 2 ={(x2−x0) 2 +(y2−y0) 2 +(z2−z0) 2 } 1/2 , obtain a maximum flight time t 2 of the laser beam from the maximum value d 2 from a formula which is t 2 =(d 2 /c)×2, and determine a light receiving window of the single laser sensor from the minimum flight time t 1 and the maximum flight time t 2 .

4 . The distance measurement device according to claim 1 , wherein
the processor is further configured to: define the measurement region by an XYZ coordinate system, obtain a distance d 21 from a provision position S 2 (x20, y20, z20) of a second laser sensor to a provision position S 1 (x10, y10, z10) of a first laser sensor from a formula which is d 21 ={(x20−x10) 2 +(y20−y10) 2 +(z20−z10) 2 } 1/2 , obtain a first flight time t 21 from a formula which is t 21 =d 21 /c, c indicate a speed of light, obtain a second flight time t 22 of interfering light that flies a longest distance among interfering light that is reflected at a point P 3 (x3, y3, z3) that is located in a section from the provision position S 2 within the measurement region and reaches the first laser sensor from a formula which is t 22 =[{(x20−x3) 2 +(y20−y3) 2 +(z20−z3) 2 } 1/2 +{(x3−x10) 2 +(y3−y10) 2 +(z3−z10) 2 } 1/2 ]/c, determine an interference risk range of the first laser sensor from the second laser sensor based on the first flight time t 21 and the second flight time t 22 , and the distance d 21 is interfering light that flies a shortest distance from among interfering light that is mixed from the second laser sensor into the first laser sensor.

5 . The distance measurement device according to claim 1 , wherein
light receiving windows of each of the sensors are periods immediately after light projection of the respective sensors and do not overlap each other, and an interference risk range of each of the sensors from another sensor is a period that is immediately after light projection by the another sensor and does not overlap the own light receiving window.

6 . The distance measurement device according to claim 1 , wherein
each of the plurality of laser sensors includes a sensor controller, a light emission circuit, and a light reception circuit, and the processor is further configured to: store a timing chart that has been designed in advance and includes information regarding the light emission cycle, a light emission delay time, and a light receiving window of the plurality of sensors, instruct the light emission circuit via the sensor controller of a first laser sensor which is selected to emit a laser beam at the light emission cycle and with the light emission delay time for the first laser sensor, instruct the light reception circuit via the sensor controller of the first laser sensor to receive reflected light from the measurement target by the light receiving window for the first laser sensor, instruct the sensor controller of the first laser sensor to calculate and return a distance to a measurement point based on time needed for the reception, select the second laser sensor based on the light emission delay time for the second laser sensor, instruct remaining laser sensors including the second laser sensor to calculate and return a distance similarly to the first laser sensor, and obtain a three-dimensional shape of the measurement target by synthesizing distance values respectively obtained from the plurality of laser sensors.

7 . The distance measurement device according to claim 1 , wherein
each of the plurality of laser sensors includes a light emitting angle control circuit that changes a light projection direction of a laser beam, and the processor instructs the light emitting angle control circuit of at least one laser sensor of the plurality of laser sensors to change a light projection direction of a laser beam of the one laser sensor to a direction in which an interference caused by direct light to the another laser sensor is avoided after a measurement handling time of the one laser sensor ends.

8 . A distance measurement method comprising:
controlling to laser beam emission timings of a plurality of laser sensors which project a laser beam and receive reflected light from a measurement target that moves within a measurement region so as to be different from each other; and driving, based on the measurement region and a provision position of the plurality of laser sensors, each of the laser sensors at a light emission cycle in which a light receiving window that receives reflected light of own light and an interference risk range are included the interference risk range being a range in which an interference is caused by a laser beam from another laser sensor.

9 . The distance measurement method according to claim 8 , wherein
the controlling includes controlling to the laser beam emission timings being deviated by light emission delay times different from each other with respect to a laser sensor to be a reference.

10 . The distance measurement device according to claim 8 , further comprising:
defining the measurement region by an XYZ coordinate system, obtaining minimum value d 1 of a point P 1 (x1, y1, z1) closest to a provision position S (x0, y0, z0) of a single laser sensor among points in the measurement region from a formula which is d 1 ={(x1−x0) 2 +(y1−y0) 2 +(z1−z0) 2 } 1/2 , obtaining a minimum flight time t 1 of the laser beam from the minimum value d 1 from a formula which is t 1 =(d 1 /c)×2, c indicate a speed of light, obtaining a maximum value d 2 of a point P 2 (x2, y2, z2) farthest from the provision position S (x0, y0, z0) among the points in the measurement region from a formula which is d 2 ={(x2−x0) 2 +(y2−y0) 2 +(z2−z0) 2 } 1/2 , obtaining a maximum flight time t 2 of the laser beam from the maximum value d 2 from a formula which is t 2 =(d 2 /c)×2, and determining a light receiving window of the single laser sensor from the minimum flight time t 1 and the maximum flight time t 2 .

Assignees

• Fujitsu Ltd

Inventors

• Tezuka Koichi
• Iida Koichi
• Sakai Katsushi
• Yanai Kosuke

Classifications

• G01S7/4812

  transmitted and received beams following a coaxial path · CPC title

• G01S17/08 Primary

  for measuring distance only (indirect measurement G01S17/46; active triangulation systems G01S17/48) · CPC title

• G01S17/894

  Three-dimensional [3D] imaging with simultaneous measurement of time-of-flight at a two-dimensional [2D] array of receiver pixels, e.g. time-of-flight cameras or flash lidar · CPC title

• G01S17/931

  of land vehicles · CPC title

• G01S17/87

  Combinations of systems using electromagnetic waves other than radio waves · CPC title