Radar device and MEMS mirror device therefor

• US 20070222678A1
• Filed: 01/24/2007
• Published: 09/27/2007
• Est. Priority Date: 03/15/2006
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Fujioka, Ryoji, Ishio, Wataru
• Granted Patent: US 7,476,846 B2
• Time in Patent Office: Days
• US Class Current: 342/372
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 7/4811 common to transmitter and receiver
• CPC Class Codes: G01S 7/4817 relating to scanning

Abstract

A radar device includes a light projecting part that generates laser light, a light projecting lens that converges the generated laser light to form a beam, a reflective mirror for reflecting the converged beam to project it in a specified search direction and for reflecting returning light from this search direction, a light receiving lens for converging the returning light reflected by the reflective mirror, and a scanning part for moving the beam in a scanning manner. There are two light receiving parts which are different in photosensitivity, and a synthesizing part outputs a synthesized signal formed by synthesizing output signals from these two light receiving parts.

Claims

1. An MEMS mirror device comprising:

a semiconductor substrate having a surface with areas arranged in a matrix form;

a plurality of semiconductor elements each formed by a semiconductor process as a mirror element with a mirror surface in different one of said areas; and

at least one photodiode each at different one of said areas.

2. A radar device comprising:

a light projecting part that generates laser light;

a first light receiving part that converts received light into a signal;

an optical system that uses an MEMS mirror and serves to form said laser light generated by said light projecting part into a beam, to project said beam in a specified search direction, to receive reflected light from said search direction and to lead said received light to said first light receiving part, said MEMS mirror having a semiconductor substrate having a surface that is mirror-finished by a semiconductor process and at least one photodiode on said surface;

a second light receiving part including said at least one photodiode formed on said MEMS mirror and having a photosensitive range for reflected light with higher brightness than the photosensitive range of said first light receiving part; and

a synthesizing part that outputs a synthesized signal formed by synthesizing outputs from said first light receiving part and said second light receiving part.

3. The radar device of claim 2 wherein said first light receiving part includes an avalanche photodiode and each of said at least one photodiode is a PIN diode.

4. The radar device of claim 2 further comprising means for driving said MEMS mirror device to thereby cause said search direction to oscillate.

5. A radar device comprising:

a light projecting part that generates laser light;

a first light receiving part that converts received light into a signal;

an optical system that uses an MEMS mirror and serves to form said laser light generated by said light projecting part into a beam, to project said beam in a specified search direction, to receive reflected light from said search direction and to lead said received light to said first light receiving part, said MEMS mirror having a semiconductor substrate having a surface with areas arranged in a matrix form, a plurality of semiconductor elements each formed by a semiconductor process as a mirror element with a mirror surface in different one of said areas, and at least one photodiode each at different one of said areas;

a second light receiving part including said at least one photodiode formed on said MEMS mirror and having a photosensitive range for reflected light with higher brightness than the photosensitive range of said first light receiving part; and

a synthesizing part that outputs a synthesized signal formed by synthesizing outputs from said first light receiving part and said second light receiving part.

6. The radar device of claim 5 wherein said first light receiving part includes an avalanche photodiode and each of said at least one photodiode is a PIN diode.

7. The radar device of claim 5 further comprising means for driving said MEMS mirror device to thereby cause said search direction to oscillate.

8. The radar device of claim 5 further comprising means for causing each of micro-mirror elements of said MEMS mirror device to oscillate to thereby cause said search direction to oscillate.

9. A radar device comprising:

a light projecting part that generates laser light;

a light projecting lens that converges said laser light generated by said light projecting part to form said generated laser light into a beam;

a reflective mirror for reflecting said converged laser light formed into said beam to thereby project said beam in a specified search direction and for reflecting returning light from said search direction;

a light receiving lens for converging said returning light reflected by said reflective mirror;

a scanning part having a mobile part and serving to move said beam in a scanning manner by driving said mobile part;

a first light receiving part for receiving said returning light converged by said light receiving lens and converting said received returning light into a signal;

a second light receiving part including at least one photodiode formed on said reflective mirror and serving to receive said returning light from said search direction and to convert said received returning signal into a signal; and

a synthesizing part that outputs a synthesized signal formed by synthesizing output signals from said first light receiving part and said second light receiving part.

10. The radar device of claim 9 wherein said second light receiving part has a photosensitive range for said returning light with higher brightness than the photosensitive range of said first light receiving part.

11. The radar device of claim 9 wherein said reflective mirror is an MEMS mirror, said MEMS mirror comprising:

a semiconductor substrate having a surface that is mirror-finished by a semiconductor process; and

said at least one photodiode.

12. The radar device of claim 9 wherein said reflective mirror is an MEMS mirror, said MEMS mirror comprising:

a semiconductor substrate having a surface with areas arranged in a matrix form, a plurality of semiconductor elements each formed by a semiconductor process as a mirror element with a mirror surface in different one of said areas, and

said at least one photodiode each at different one of said areas.

13. The radar device of claim 12 wherein said scanning part moves said beam in said scanning manner by causing the mirror elements of said MEMS mirror to oscillate.

14. The radar device of claim 9 wherein said first light receiving part includes an avalanche photodiode and each of said at least one photodiode formed on said reflective mirror is a PIN diode.

15. The radar device of claim 11 wherein said first light receiving part includes an avalanche photodiode and each of said at least one photodiode formed on said reflective mirror is a PIN diode.

16. The radar device of claim 14 wherein said synthesizing part compares the value of the output signal from said first light receiving part and a multiplied value of the output signal from said second light receiving part and determines a reverse bias voltage to be applied to said avalanche photodiode for making the value of the output signal from said first light receiving part to become equal to said multiplied value.

17. The radar device of claim 15 wherein said synthesizing part compares the value of the output signal from said first light receiving part and a multiplied value of the output signal from said second light receiving part and determines a reverse bias voltage to be applied to said avalanche photodiode for making the value of the output signal from said first light receiving part to become equal to said multiplied value.

18. The radar device of claim 9 wherein said light receiving lens has a light receiving area that is larger than the light receiving area of said at least one photodiode.

19. The radar device of claim 9 wherein said light receiving lens has a light receiving area that is larger than the light receiving area of said light projecting lens.