Distance measurement apparatus

Patent metadata

Field	Value
Publication number	US-11914075-B2
Application number	US-201916445358-A
Country	US
Kind code	B2
Filing date	Jun 19, 2019
Priority date	Jul 24, 2018
Publication date	Feb 27, 2024
Grant date	Feb 27, 2024

Abstract

A distance measurement apparatus includes: a laser light source configured to emit emitted light to be applied to an object to be measured; a laser light source control circuit configured to control the laser light source; a MEMS mirror configured to two-dimensionally scan the object with the emitted light; a reflecting member configured to cover a part of a scan region, and reflect the emitted light; and a light detector configured to receive reflected light from the object to be measured and reflected light from the reflecting member, and output a received light signal. The laser light source control circuit sets, to a threshold value, an amount of the emitted light obtained when output of the light detector is saturated, and controls an amount of the emitted light such that the amount of the emitted light is less than the threshold value.

First claim

What is claimed is:

1. A distance measurement apparatus for applying laser light to an object to be measured and measuring a distance to the object to be measured, based on light reflected by the object to be measured, the distance measurement apparatus comprising:
a laser light source configured to emit the laser light;
a laser light source control circuit, the laser light source control circuit comprising a processor for executing a program, and a storage device in which the program is stored, the processor executing the program to perform the operation of controlling the laser light source;
scanning means for two-dimensionally scanning the object to be measured with the laser light;
a casing configured to store the scanning means;
an opening formed in the casing, the opening being opened toward the object to be measured, the opening allowing the object to be measured to be exposed to the scanning means;
a reflecting means fixed to the casing for covering a part of a scan region by the laser light or a periphery of the scan region and reflecting the laser light; and
a light receiving means for receiving first light reflected by the object to be measured and second light reflected by the reflecting means, and outputting a received light signal,
wherein the laser light source control circuit is configured to apply a feedback control to the laser light source based on a feedback of the second light reflected from the reflecting means.

2. The distance measurement apparatus according to claim 1 , wherein the laser light source control circuit reduces power source voltage of the laser light source at timing when the light receiving means receives light reflected by the reflecting means.

3. The distance measurement apparatus according to claim 2 , wherein
the scanning means performs while turning, at an end of the scan region, a scanning line extending in a first direction, scanning with the laser light in a second direction orthogonal to the first direction, and
the reflecting means covers a turning position of the scanning line, and forms a region that allows the laser light to pass therethrough, between the turning position and another turning position adjacent to the turning position.

4. The distance measurement apparatus according to claim 3 , wherein change of an intensity of the received light signal from a predetermined reference value is calculated as a signal change amount and when the signal change amount is greater than an allowable value, output of the laser light source is adjusted based on the signal change amount.

5. The distance measurement apparatus according to claim 2 , wherein change of an intensity of the received light signal from a predetermined reference value is calculated as a signal change amount and when the signal change amount is greater than an allowable value, output of the laser light source is adjusted based on the signal change amount.

6. The distance measurement apparatus according to claim 1 , wherein the laser light source control circuit shortens a pulse width of the laser light at timing when the light receiving means receives light reflected by the reflecting means.

7. The distance measurement apparatus according to claim 6 , wherein
the scanning means performs while turning at an end of the scan region, a scanning line extending in a first direction, scanning with the laser light in a second direction orthogonal to the first direction, and
the reflecting means covers a turning position of the scanning line and forms a region that allows the laser light to pass therethrough, between the turning position and another turning position adjacent to the turning position.

8. The distance measurement apparatus according to claim 7 , wherein change of an intensity of the received light signal from a predetermined reference value is calculated as a signal change amount and when the signal change amount is greater than an allowable value, output of the laser light source is adjusted based on the signal change amount.

9. The distance measurement apparatus according to claim 6 , wherein change of an intensity of the received light signal from a predetermined reference value is calculated as a signal change amount and when the signal change amount is greater than an allowable value, output of the laser light source is adjusted based on the signal change amount.

10. The distance measurement apparatus according to claim 1 , wherein
the scanning means performs while turning at an end of the scan region, a scanning line extending in a first direction, scanning with the laser light in a second direction orthogonal to the first direction, and
the reflecting means covers a turning position of the scanning line and forms a region that allows the laser light to pass therethrough, between the turning position and another turning position adjacent to the turning position.

11. The distance measurement apparatus according to claim 10 , wherein change of an intensity of the received light signal from a predetermined reference value is calculated as a signal change amount and when the signal change amount is greater than an allowable value, output of the laser light source is adjusted based on the signal change amount.

12. The distance measurement apparatus according to claim 1 , wherein change of an intensity of the received light signal from a predetermined reference value is calculated as a signal change amount and when the signal change amount is greater than an allowable value, output of the laser light source is adjusted based on the signal change amount.

13. The distance measurement apparatus of claim 1 , wherein the feedback control is configured such that an amount of the laser light emitted by the laser light source is less than a threshold value and avoids a saturation of an output of the light receiving means, and the threshold value is configured based on an amount of light at which an output of the light receiving means is saturated.

Assignees

• Mitsubishi Electric Corp

Inventors

• Takagawa Yosuke
• Kawai Masahiro

Classifications

• G01S7/4817 Primary

  relating to scanning · CPC title

• G01S7/484

  Transmitters · CPC title

• G01S17/10

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

• G02B26/0816

  by means of one or more reflecting elements · CPC title

• G02B26/101

  with both horizontal and vertical deflecting means, e.g. raster or XY scanners (colour television using laser beams scanning a display screen H04N9/3129) · CPC title