Laser radar apparatus that measures direction and distance of an object

• US 20080316463A1
• Filed: 02/05/2008
• Published: 12/25/2008
• Est. Priority Date: 02/06/2007
• Status: Active Grant

• Current Assignee: Denso PS Corporation (DENSO Corporation)
• Original Assignee: Denso PS Corporation (DENSO Corporation)
• Inventors: Tanaka, Hideyuki, Konosu, Koji, Nojiri, Tadao, Okada, Masanori
• Granted Patent: US 7,580,117 B2
• Time in Patent Office: Days
• US Class Current: 356/4.01
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 7/4812 transmitted and received beams following a coaxial path
• CPC Class Codes: G01S 7/4813 Housing arrangements
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G02B 26/0816 by means of one or more reflecting elements

Abstract

There is provided a laser radar including laser beam generating means, photo detecting means, a mirror, light deflecting means, and rotation driving means. The laser beam generating means emits a laser beam having an axis thereof. The photo detecting means detects a reflected laser beam that is reflected back by an object. The mirror includes a through-hole that passes the laser beam and a reflecting surface that reflects a reflected laser beam reflected back by the object toward the photo detecting means. The light deflecting means deflects the laser beam toward a measuring region and reflects the reflected laser beam from the object toward the mirror. The rotation driving means rotates the light deflecting means so as to direct the laser beam toward the measuring region.

Claims

1. A laser radar apparatus that measures the distance of an object and the direction to the object, the object being located in a measurement range from the laser radar apparatus, comprising:

laser beam generating means for generating a laser beam having an axis thereof and emitting the laser beam toward the measurement range;

photo detecting means for detecting a reflected laser beam that is reflected back by the object located in the measurement range;

a mirror assembly comprising;

a through-hole that pierces the mirror assembly being coaxial with the axis of the laser beam emitted from the laser beam generating means and passes the laser beam emitted from the laser beam generating means; and

a reflecting surface that is arranged to be at a predetermined angle to the axis of the laser beam emitted from the laser beam generating means and reflects a reflected laser beam reflected back by the object toward the photo detecting means;

light deflecting means for deflecting the laser beam emitted from the laser beam generating means toward the measurement range and deflecting the laser beam reflected back by the object located in the measurement range toward the mirror assembly, the light deflecting means having a rotation axis thereof and a mirror surface; and

rotation driving means for rotating the light deflecting means around the rotation axis of light deflecting means such that the mirror surface of the light deflecting means is turned to face in the direction of the measurement range.

2. The apparatus according to claim 1, wherein

the rotation axis of the light deflecting means is coincident with the axis of the laser beam emitted from the laser beam generating means,

the light deflecting means has a concave shaped surface that has a focal point located on the axis of the rotation axis of the light deflecting means, and

the concave shaped surface of the light deflecting means deflects the laser beam emitted from the laser beam generating means toward the measurement range and deflects the laser beam reflected back by the object located in the measurement range toward the mirror assembly.

3. The apparatus according to claim 1, further comprising:

an optical element for transmitting the laser beam emitted from the laser beam generating means toward the measurement range and reflecting the laser beam reflected back by the object located in the measurement range via the light deflecting means, and

the through-hole of the mirror assembly is at least partially covered by the optical element.

4. The apparatus according to claim 1, wherein

the through-hole of the mirror assembly is completely empty.

5. The apparatus according to claim 1, further comprising:

beam splitting means for splitting the laser beam emitted from the laser beam generating means into a first laser beam and a second laser beam; and

control means for adjusting the output of the laser beam generating means,

wherein the first laser beam enters to the concave shaped surface of the light deflecting means,

the second laser beam enters to the photo detecting means to measure its intensity, and

the control means adjusts the output of the laser beam generating means based on the measured intensity of the second laser beam.

6. The apparatus according to claim 5, wherein

the beam splitting means includes a half-silvered mirror.

7. The apparatus according to claim 5, wherein

the beam splitting means includes a mirror device that blocks at least a part of the laser beam and the reflected laser beam passing through the through-hole of the mirror.

8. The apparatus according to claim 1, wherein

a peripheral surface of the through-hole has a projected image that obtained by the through-hole projecting a plane perpendicular to the axis of the laser beam emitted from the laser beam generating means, and the projected image has an approximately circular shape.

9. The apparatus according to claim 1, further comprising:

laser beam collimating means for collimating the laser beam emitted from the laser beam generating means into a laser beam of parallel rays,

wherein collimating means is located on the optical path of the laser beam emitted from the laser beam generating means.

10. The apparatus according to claim 1, further comprising:

a cover case that has a slit through which the laser beam emitted from the laser beam generating means or the reflected laser beam is reflected back by the object

wherein the slit is arranged to be located on at least one of the optical paths of the laser beam emitted from the laser beam generating means and the reflected laser beam reflected back from the object.

11. The apparatus according to claim 10, wherein

the slit of the cover case has the shape of cylinder having a circular shaped cross section.

12. The apparatus according to claim 1, further comprising:

beam transforming means for transforming the laser beam emitted from the laser beam generating means to a transferred laser beam having a predetermined projection pattern, the beam transforming means being arranged to be located on the optical path of the laser beam emitted from the laser beam generating means between the laser beam generating means and the measurement range,

wherein the beam transforming means transforms the laser beam emitted from the laser beam generating means so as to have a predetermined projection pattern that covers a larger area than the cross sectional area of the incident laser beam.

13. The apparatus according to claim 12, wherein

the mirror surface of the light deflecting means has a flat reflecting portion having a flat mirror surface and a concave reflecting portion having a concave-shaped mirror surface, the concave-shaped mirror surface having a focal point located on the rotation axis of the light deflecting means,

the concave-shaped mirror surface of the light deflecting means deflects the laser beam reflected back by the object located in the measurement range toward the mirror assembly, and

the flat mirror surface of the light deflecting means deflects the laser beam emitted from the laser beam generating means toward the measurement range.

14. The apparatus according to claim 13, wherein

the beam transforming means is embedded in the flat mirror surface of the light deflecting means such that the laser beam emitted from the laser beam generating means is transformed to have the predetermined projection pattern in the measurement range.

15. The apparatus according to claim 12, wherein

the beam transforming means is arranged to be located on the axis of the laser beam emitted from the laser beam generating means between the laser beam generating means and the through-hole of the mirror assembly.

16. The apparatus according to claim 12, wherein

the beam transforming means includes a diffraction grating.

17. The apparatus according to claim 12, wherein

the predetermined projection pattern includes a bright area and a dark area enclosed by the bright area, wherein a larger quantity of light shines upon the bright area than the dark area.

18. The apparatus according to claim 12, wherein

the predetermined projection pattern includes a pair of bright areas and a dark area put between the pair of the bright areas.

19. The apparatus according to claim 18, wherein

the predetermined projection pattern is designed such that the pair of the bright areas are located on the rotation axis of the light deflecting means with a predetermined spacing.