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

Patent metadata

Field	Value
Publication number	US-2018106903-A1
Application number	US-201715715296-A
Country	US
Kind code	A1
Filing date	Sep 26, 2017
Priority date	Oct 14, 2016
Publication date	Apr 19, 2018
Grant date	—

Abstract

A distance measuring device executes a collection process that includes driving a MEMS mirror in each of a plurality of sensors and collecting a drive voltage of the MEMS mirror satisfying a given condition, executes a drive frequency determination process that includes determining a drive frequency of the MEMS mirror when measuring distances by the plurality of sensors based on the drive voltage of the MEMS mirror, and executes a control signal generation process that includes generating and transmitting a control signal to the plurality of sensors, the control signal including configuration information specifying the drive frequency as a drive frequency of the MEMS mirror in each of the plurality of sensors, the configuration information including the drive frequency determined by the drive frequency determination process.

First claim

What is claimed is:

1 . A distance measuring device comprising:
a memory; a processor coupled to the memory and configured to execute a collection process that includes driving a MEMS mirror in each of a plurality of sensors and collecting a drive voltage of the MEMS mirror satisfying a given condition, the plurality of sensors having the MEMS mirror that controls an emission direction of a laser beam with a same drive frequency, execute a drive frequency determination process that includes determining a drive frequency of the MEMS mirror when measuring distances by the plurality of sensors based on the drive voltage of the MEMS mirror, the drive voltage being collected by the collection process for each of the plurality of drive frequencies, and execute a control signal generation process that includes generating and transmitting a control signal to the plurality of sensors, the control signal including configuration information specifying the drive frequency as a drive frequency of the MEMS mirror in each of the plurality of sensors, and the configuration information including the drive frequency determined by the drive frequency determination process.

2 . The distance measuring device according to claim 1 ,
wherein the drive voltage that satisfies the given condition is a minimum drive voltage at which a swing angle of the MEMS mirror is equal to or larger than a threshold value or an upper limit value of a preset drive voltage.

3 . The distance measuring device according to claim 1 , further comprising:
the plurality of sensors; wherein each of the plurality of sensors includes a drive signal generation circuit configured to generate a drive signal of the MEMS mirror based on a drive voltage at which the swing angle of the MEMS mirror when the MEMS mirror is driven at the drive frequency specified by the control signal is equal to or larger than a given angle range or based on an upper limit value of a preset drive voltage, the control signal generation process includes generating a control signal and transmitting the control signal to the plurality of sensors, the control signal including information specifying each of the plurality of drive frequencies as the drive frequency of the MEMS mirror, and the collection process includes collecting the drive voltage of the drive signal generated in the drive signal generation circuit of the plurality of sensors.

4 . The distance measuring device according to claim 3 ,
wherein at least one sensor of the plurality of sensors includes a master clock generation circuit configured to generate a master clock of the drive frequency specified as the control signal, the plurality of sensors includes a phase synchronization circuit configured to synchronize a phase of a sensor clock used for generating a drive signal for driving the MEMS mirror with a phase of the master clock, the control signal generation process includes transmitting the control signal to a first sensor of the plurality of sensors, the first sensor including the master clock generation circuit, and the first sensor transfers the generated master clock to another sensor upon receiving the control signal.

5 . The distance measuring device according to claim 4 ,
wherein the drive signal generation circuit in each of the plurality of sensors controls the angle of the MEMS mirror in a first direction with the drive frequency and generates the drive signal that controls the angle of the MEMS mirror in a second direction different from the first direction to one direction, and each of the plurality of sensors further includes an offset adjustment circuit configured to perform offset adjustment of the phase of the sensor clock based on the angle of the MEMS mirror in the second direction.

6 . The distance measuring device according to claim 5 ,
wherein each of the plurality of sensors further includes a correction circuit configured to calculate a correction amount of the phase of the sensor clock based on a correction amount table indicating a correspondence between an angle of the MEMS mirror in the second direction and a phase shift amount in the drive signal, and an angle of the MEMS mirror in the second direction.

7 . The distance measuring device according to claim 5 ,
wherein each of the plurality of sensors further includes a phase adjustment circuit configured to adjust the phase of the master clock.

8 . The distance measuring device according to claim 1 ,
wherein the plurality of drive frequencies for collecting the drive voltage of the MEMS mirror is a frequency between a minimum frequency and a maximum frequency among resonance frequencies of the plurality of MEMS mirrors.

9 . The distance measuring device according to claim 1 ,
wherein the drive frequency determination process includes determining a drive frequency at which the sum of drive power of the MEMS mirrors of the plurality of sensors is minimized.

10 . A distance measuring method performed by a computer, the method comprising:
executing, by a processor of the computer, a collection process that includes driving a MEMS mirror in each of a plurality of sensors and collecting a drive voltage of the MEMS mirror satisfying a given condition, the plurality of sensors having the MEMS mirror that controls an emission direction of a laser beam with a same drive frequency, executing, by the processor of the computer, a drive frequency determination process that includes determining a drive frequency of the MEMS mirror when measuring distances by the plurality of sensors based on the drive voltage of the MEMS mirror, the drive voltage being collected by the collection process for each of the plurality of drive frequencies, executing, by the processor of the computer, a control signal generation process that includes generating and transmitting a control signal to the plurality of sensors, the control signal including configuration information specifying the drive frequency as a drive frequency of the MEMS mirror in each of the plurality of sensors, the configuration information including the drive frequency determined by the drive frequency determination process, and executing, by the processor of the computer, a measurement process that includes obtaining a result of measurement of each of the plurality of sensors by driving the MEMS mirror with the drive frequency specified by the control signal, the measurement result including a measurement result of a distance from the sensor to an object.

11 . The distance measuring method according to claim 10 ,
wherein the control signal generation process further includes
selecting first sensor of the plurality of sensors,
transmitting the control signal to the first sensor,
causing the first sensor to generate a master clock of the drive frequency specified by the control signal and transfer the generated master clock to another sensor, and
causing the phase of the sensor clock used for generating a drive signal for driving the MEMS mirror to be synchronized with a phase of the master clock in each of the plurality of sensors.

12 . The distance measuring method according to claim 11 , further comprising:
causing each of the plurality of sensors
to control the angle of the MEMS mirror in the first direction with the drive frequency and the angle of the MEMS mirror in a second direction different from the first direction to one direction by each of the plurality of sensors, and
to calculate a correction amount of the phase of the sensor clock by referring to a correction amount table indicating a correspondence between an angle of the MEMS mirror in the second direction and a phase shift amount in the sensor c

Assignees

• Fujitsu Ltd

Inventors

• Iida Koichi
• Morikawa Takeshi
• Kawai Jun
• Tezuka Koichi
• Yanai Kosuke

Classifications

• G01S17/87

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

• G01S7/497

  Means for monitoring or calibrating · CPC title

• G01S7/4817 Primary

  relating to scanning · CPC title

• G01S17/10 Primary

  using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) · CPC title

• G01S17/42

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46) · CPC title