Distance measuring device and laser beam projector therefor

Abstract

A laser beam projector has a laser light source that outputs a laser beam, a light projecting mirror for reflecting the laser beam outputted from the laser light source, a mirror driving device for oscillating the light projecting mirror so as to scan a specified area with the laser beam and piezoelectric elements attached to a back surface of the light projecting mirror. As a voltage is applied to the piezoelectric elements, the curvature of the reflecting surface of the light projecting mirror can be changed and the visibility angle of the light beam projector can be varied. A distance measuring device is formed with such a laser beam projector together with a laser beam receiver for receiving reflected waves of the laser beam from an object and a control unit for measuring the distance to the object based on the difference between the time of projecting the laser beam and the time of receiving the reflected waves by the laser beam receiver as well as the direction of the object from the direction of the projected laser beam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a distance measuring device using a laser beam projector embodying this invention.

FIG. 2 is a diagonal view of the light projecting mirror.

FIG. 3 shows the reflection of a laser beam when the light projecting mirror is deformed.

FIG. 4 is a diagonal view of the light projecting mirror when it is deformed.

FIGS. 5A and 5B show the visibility angle of the laser beam.

FIG. 6 is a flowchart for operating the mirror.

FIGS. 7A, 7B and 7C show another light projecting mirror according to another embodiment of the invention.

Claims

1. A laser beam projector comprising: a laser light source that outputs a laser beam;a light projecting mirror for reflecting said laser beam outputted from said laser light source;a mirror driving device for oscillating said light projecting mirror and thereby scanning a specified area with said laser beam; andat least one piezoelectric element attached to a back surface of said light projecting mirror.

2. The laser beam projector of claim 1 having a plurality of piezoelectric elements attached to said back surface of said light projecting mirror.

3. The laser beam projector of claim 1 further comprising actuating means for actuating said at least one piezoelectric element according to the angle of oscillation of said light projecting mirror.

4. The laser beam projector of claim 2 further comprising actuating means for actuating said piezoelectric elements according to the angle of oscillation of said light projecting mirror.

5. The laser beam projector of claim 3 wherein said actuating means actuates said at least one piezoelectric element when said angle of oscillation of said light projecting mirror is near the maximum angle of oscillation so as to increase the curvature of the reflecting surface of said light projecting mirror.

6. The laser beam projector of claim 4 wherein said actuating means actuates said piezoelectric elements when said angle of oscillation of said light projecting mirror is near the maximum angle of oscillation so as to increase the curvature of the reflecting surface of said light projecting mirror.

7. A distance measuring device comprising: a laser beam projector that includes: a laser light source that outputs a laser beam;a light projecting mirror for reflecting said laser beam outputted from said laser light source;a mirror driving device for oscillating said light projecting mirror and thereby scanning a specified area with said laser beam; andat least one piezoelectric element attached to a back surface of said light projecting mirror;a laser beam receiver for receiving reflected waves of said laser beam from an object; anda control unit for measuring the distance to said object based on the difference between the time of projecting said laser beam from said laser beam projector and the time of receiving said reflected waves by said laser beam receiver and the direction of said object from the direction of the projected laser beam.

8. The distance measuring device of claim 7 wherein said laser beam projector has a plurality of piezoelectric elements attached to said back surface of said light projecting mirror.

9. The distance measuring device of claim 7 wherein said laser beam projector further comprises actuating means for actuating said at least one piezoelectric element according to the angle of oscillation of said light projecting mirror.

10. The distance measuring device of claim 8 wherein said laser beam projector further comprises actuating means for actuating said piezoelectric elements according to the angle of oscillation of said light projecting mirror.

11. The distance measuring device of claim 9 wherein said actuating means actuates said at least one piezoelectric element when said angle of oscillation of said light projecting mirror is near the maximum angle of oscillation so as to increase the curvature of the reflecting surface of said light projecting mirror.

12. The distance measuring device of claim 10 wherein said actuating means actuates said piezoelectric elements when said angle of oscillation of said light projecting mirror is near the maximum angle of oscillation so as to increase the curvature of the reflecting surface of said light projecting mirror.