Distance measuring device

• US 5,493,388 A
• Filed: 08/11/1994
• Issued: 02/20/1996
• Est. Priority Date: 09/02/1993
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Adachi, Tadashi
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US08/289,037
• Time in Patent Office: 558 Days
• Field of Search: 356/5.01, 356/5.02, 359/198, 359/216, 359/217, 250/334, 250/347
• US Class Current: 356/5.01
• CPC Class Codes: G01S 7/4812 transmitted and received beams following a coaxial path
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G02B 26/12 using multifaceted mirrors

Abstract

A distance measuring device of laser beam using type has a laser diode for producing laser beams. A scanning mechanism projects the laser beams against an object and includes a polygon mirror to and by which the laser beams are directed and reflected. A receiver mechanism receives the laser beams reflected by the object. A control unit measures the period required for the laser beams to make the trip around the object. The polygon mirror is so arranged as to be rotated about a first axis and swung about a second axis.

Claims

1. A distance measuring device of laser beam using type, comprising:

first means for producing laser beams;

second means for projecting said laser beams against an object, said second means including a polygon mirror to and by which said laser beams are directed and reflected;

third means for receiving the laser beams reflected by said object; and

fourth means for measuring the period required for said laser beams to make the trip around the object,

wherein said polygon mirror is so arranged as to be rotated about a first axis thereof and swung about a second axis thereof.

2. A distance measuring device as claimed in claim 1, in which said first axis is perpendicular to said second axis.

3. A distance measuring device as claimed in claim 2, in which said third means comprises:

a single laser beam receiver; and

two optical tracks through which the laser beams reflected by said object are led to said laser beam receiver, said two optical tracks being arranged symmetrical with respect to an imaginary plane along which the first axis of said polygon mirror travels during the swinging movement of the polygon mirror.

4. A distance measuring device as claimed in claim 3, in which each of the two optical tracks comprises one of mirror surfaces of said polygon mirror and at least one fixed mirror.

5. A distance measuring device as claimed in claim 3, in which each of the two optical tracks comprises:

one of mirror surfaces of said polygon mirror;

a first inclined fixed mirror arranged beside the polygon mirror;

a second inclined fixed mirror arranged above said first inclined fixed mirror; and

a reduction telescope arranged between said second inclined fixed mirror and said laser beam receiver.

6. A distance measuring device as claimed in claim 5, in which said reduction telescope is equipped with an interference filter.

7. A distance measuring device as claimed in claim 3, in which each of the two optical tracks comprises:

one of mirror surfaces of said polygon mirror; and

a concave lens arranged beside said polygon mirror.

8. A distance measuring device as claimed in claim 7, in which said concave lens has its focus at the laser beam receiver.

9. A distance measuring device as claimed in claim 8, in which said polygon mirror includes:

a first polygon mirror part to and by which the laser beams from said first means are directed and reflected; and

a second polygon mirror part to and by which the laser beams reflected by said object are directed and reflected,

wherein mirror surfaces of said second polygon mirror part are larger than those of said first polygon mirror part.

10. A distance measuring device as claimed in claim 4, in which said second means further comprises:

an electric motor mounting thereon said polygon mirror to rotate the same in a given direction;

a nodding plate mounting thereon said electric motor, said nodding plate being pivotally mounted on a fixed structure; and

a step motor for stepwisely pivot the nodding plate.

11. A distance measuring device as claimed in claim 10, in which said second means further comprises:

an angle sensor for sensing the angular position of said nodding plate relative to said fixed structure; and

means for operating said step motor in a manner to jump up the nodding plate to its uppermost angular position when said angle sensor senses the lowermost angular position of said nodding plate.

12. A distance measuring device as claimed in claim 4, in which said second means further comprises:

an electric motor mounting thereon said polygon mirror to rotate the same in a given direction;

means for permitting a unit consisting of said electric motor and said polygon mirror to swing about said second axis;

a step motor; and

a link mechanism for pivoting said unit about said second axis with an aid of said step motor.

13. A distance measuring device of laser beam using type, comprising:

means for producing laser beams;

a polygon mirror having mirror surfaces to and by which said laser beams are directed and reflected;

an electric motor on which said polygon mirror is mounted to be rotated about a first axis by the same;

a nodding plate on which said electric motor is mounted, said nodding plate being swung about a second axis which is perpendicular to said first axis;

a step motor for stepwisely swinging said nodding plate about said second axis;

a single laser beam receiver; and

two optical tracks through which the laser beams reflected by said object are led to said laser beam receiver, said two optical tracks being arranged symmetrical with respect to an imaginary plate along which said first axis travels during swinging movement of said nodding plate about said second axis, each optical truck including one of mirror surfaces of said polygon mirror, a first inclined fixed mirror arranged beside the polygon mirror, a second inclined fixed mirror arranged above said first inclined fixed mirror and a reduction telescope arranged between said second inclined fixed mirror and said laser beam receiver.

14. A distance measuring device of laser beam using type, comprising:

means for producing laser beams;

a polygon mirror including a first polygon mirror part and a second polygon mirror part which are coaxially coupled, mirror surfaces of said second polygon mirror part being larger than those of said first polygon mirror part, said polygon mirror being so arranged that the laser beams are directed to and reflected by the mirror surfaces of said first polygon mirror part;

an electric motor on which said polygon mirror is mounted to be rotated about a first axis by the same;

means for permitting said electric motor to pivot about a second axis which is perpendicular to said first axis;

a step motor; and

a link mechanism for pivoting said electric motor about said second axis with an aid of said step motor.