Laser beam type distance measuring device

• US 6,023,323 A
• Filed: 04/28/1998
• Issued: 02/08/2000
• Est. Priority Date: 10/20/1994
• Status: Expired due to Term

• Current Assignee: IHI Aerospace Company Limited (IHI Corporation), Ishikawajima-Harima Heavy Industries Company Limited, Olympus Optical Company Ltd. (Olympus Corporation)
• Original Assignee: Nissan Motor Co., Ltd., Olympus Optical Company Ltd. (Olympus Corporation)
• Inventors: Kato, Masahiko, Matsuzaki, Hiroshi, Iijima, Takahiko
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/066,885
• Time in Patent Office: 651 Days
• Field of Search: 356/4.01, 356/5.01-5.15, 180/169
• US Class Current: 356/5.06
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 7/4813 Housing arrangements
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/4818 using optical fibres
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A laser beam type distance measuring device comprising a laser beam emitter; a laser beam receiver having a going laser beam sensor and a returning laser beam sensor; an electrical signal processing circuit connected to the going and returning laser beam sensors; a returning laser beam guide way leading to the returning laser beam sensor; a polygon mirror for reflecting a going laser beam from the laser beam emitter toward a remote object and reflecting a returning laser beam from the object toward the returning laser beam guide way along which the returning laser beam travels to the returning laser beam sensor; and a reference optical track having one end directed to the laser beam emitter and the other end directed to the going laser beam sensor, so that a first part of the going laser beam from the laser beam emitter travels to the going laser beam sensor through the reference optical track. In the present invention, there is further provided a laser transmitting member, such as an optical fiber, which is arranged in parallel with path to and from the object. The laser transmitting member has one end directed to the laser beam emitter and the other end directed to the returning laser beam sensor, so that a second part of the going laser beam from the laser beam emitter travels to the returning laser beam sensor through the laser transmitting member.

Claims

1. An optical device for measuring the distance to a remote object, the device comprising:

a light source;

a light receiver having a going light sensor and a returning light sensor;

an electrical signal processing unit connected to said going and returning light sensors;

a returning light guide way leading to said returning light sensor;

an optical member for reflecting going light from said light source toward the remote object and for reflecting returning light from the remote object toward said returning light guide way along which said returning light travels to the returning light sensor;

a reference optical track having one end directed to said light source and the other end directed to said going light sensor, so that a first part of the going light from said light source travels to said going light sensor through said reference optical track; and

a light transmitting member having predetermined length and having a first end directed to said light source and a second end directed to said returning light sensor, so that a second part of the going light from said light source travels to said returning light sensor through said light transmitting member,

wherein said electric signal processing unit computes a calculated length of said light transmitting member based on said first and second parts of the going light, and compares said calculated and predetermined lengths for effecting a temperature compensation of the measured distance to the object.

2. The optical device as claimed in claim 1, in which said light transmitting member is an optical fiber.

3. The optical device as claimed in claim 1, in which said electric signal processing unit detects a phase difference between said first part of the going light which has passed through said reference optical track and said second part of the going light which has passed through said light transmitting member.

4. The optical device as claimed in claim 3, in which said electric signal processing unit corrects the phase of said first part of the going light with reference to the detected phase difference.

5. The optical device as claimed in claim 1, in which said returning light guide way comprises two identical optical tracks.

6. The optical device as claimed in claim 2, in which said optical fiber has a coiled middle portion.

7. The optical device as claimed in claim 1, wherein said optical member is a polygon mirror, and said optical device further comprising:

a motor for rotating said polygon mirror about a first axis; and

a motor for rotating said polygon mirror about a second axis which is perpendicular to said first axis.

8. A device for optically measuring a distance to a remote object based on a phase difference between a going light emitted from a light source toward the object and a returning light reflected by the object, comprising:

a light transmitting member having a predetermined optical length as a reference, said light transmitting member exhibiting substantially no change in length even when temperature changes; and

a temperature compensating means for measuring the length of said light transmitting member based on a phase difference between the going light emitted from the light source and the going light traveling through said light transmitting member, and for compensating a measured distance to the object by means of an error between a value corresponding to said reference and a value corresponding to said measured optical length of said light transmitting member.