Deflectable micro-mirror

• US 6,449,079 B1
• Filed: 11/20/2000
• Issued: 09/10/2002
• Est. Priority Date: 12/16/1998
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Herrmann, Falk
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US09/622,387
• Time in Patent Office: 659 Days
• Field of Search: 359/223, 359/224, 359/225, 359/291, 359/292, 359/295, 359/196, 359/197, 359/198, 359/199, 359/212, 359/213, 359/214
• US Class Current: 359/214.1
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 26/0858 the reflecting means being moved or deformed by piezoelectric means

Abstract

An oscillatory micromirror having a cantilevered mirror surface is joined using at least one torsion axis formed by at least one torsion beam mounted on the mirror surface, to a support member that surrounds at least portions of the mirror surface. There is located between at least one of the torsion beams and the support member a flexural beam that performs a flexural oscillation which induces a torsional oscillation of the mirror surface about the torsion axis. At a suitable frequency, large amplitudes of the torsional oscillation may be provided by small amplitudes of the flexural oscillation.

Claims

1. An oscillatory micromirror comprising:

a cantilevered mirror surface;

at least one torsion beam mounted on the cantilevered mirror surface;

a support member surrounding at least a portion of the cantilevered mirror surface;

at least one flexural beam;

wherein;

the cantilevered mirror surface is joinable to the support member by at least one torsion axis formed by the at least one torsion beam;

the at least one flexural beam is located between at least one of the at least one torsion beam and the support member, the at least one flexural beam providing a flexural oscillation for inducing a torsional oscillation of the cantilevered mirror surface about the at least one torsion axis; and

an amplitude of the flexural oscillation is substantially smaller than an amplitude of the torsional oscillation.

2. The oscillatory micromirror of claim 1, wherein at least one of the at least one torsion axis is not an axis of symmetry of the cantilevered mirror surface.

3. The oscillatory micromirror of claim 1, wherein at least one of the at least one torsion axis is formed by the at least one torsion beam, the at least one torsion beam including two oppositely located torsion beams.

4. The oscillatory micromirror of claim 1, wherein the flexural oscillation occurs at a frequency corresponding to a resonant torsional frequency of the torsional oscillation about the at least one torsion axis.

5. The oscillatory micromirror of claim 1, wherein a frequency of the flexural oscillation is set so that a resonant frequency of the flexural oscillation is substantially different from a resonant torsonial frequency of the torsional oscillation.

6. The oscillatory micromirror of claim 1, wherein an orientation defined by a longitudinal axis of the at least one flexural beam is different from another orientation of the at least one torsion axis.

7. The oscillatory micromirror of claim 1, wherein the at least one flexural beam and at least one of the at least one torsion beam are joined to one another at an angle of 90°

.

8. The oscillatory micromirror of claim 1, wherein at least one of the cantilevered mirror surface, the at least one torsion beam and the at least one flexural beam is at least locally metallized on its surface.

9. The oscillatory micromirror of claim 1, wherein at least one of the cantilevered mirror surface, the at least one torsion beam and the at least one flexural beam includes silicon.

10. The oscillatory micromirror of claim 1, further comprising:

at least one of a thermoelectric flexural transducer and a piezoelectric flexural transducer for mounting on the at least one flexural beam on at least one side and for inducing the flexural oscillation in the at least one flexural beam via an external electrical circuit.

11. The oscillatory micromirror of claim 10, wherein at least one of the at least one torsion beam and the at least one flexural beam are made using silicon that is doped at a surface to form a doped silicon layer that is at least one of a piezoresistor, a piezoresistive transducer and a thermomechanical flexural transducer.

12. The oscillatory micromirror of claim 1, further comprising:

at least one of a piezoresistive transducer and a piezoelectric transducer for at least mounting locally on the at least one torsion beam and for detecting an amplitude of the torsional oscillation.

13. The oscillatory micromirror of claim 12, further comprising:

at least one of a thermomechanical flexural transducer and a piezoelectric flexural transducer in the at least one flexural beam, wherein the at least one of the piezoresistive transducer and the piezoelectric transducer is located in a feedback branch of a resonator, the resonator controlling the at least one of the thermomechanical flexural transducer and the piezoelectric flexural transducer so that a measurement signal of the at least one of the piezoresistive transducer and the piezoelectric transducer, which detects an amplitude of the torsional oscillation, regulates a frequency of the flexural oscillation.

14. The oscillatory micromirror of claim 1, wherein the oscillatory micromirror is made using a surface micromechanical patterning, the patterning including a silicon etching of a silicon wafer having an electrical triggering and interconnect system.