MEMS device having simplified drive

• US 20050253055A1
• Filed: 11/09/2004
• Published: 11/17/2005
• Est. Priority Date: 05/14/2004
• Status: Active Grant

• Current Assignee: Microvision, Inc.
• Original Assignee: Microvision, Inc.
• Inventors: Brown, Dean R., Tauscher, Jason B., Montague, Thomas W., Sprague, Randall B., Davis, Wyatt O., Lewis, John R., Yan, Jun, Brown, Chancellor W.
• Granted Patent: US 7,442,918 B2
• Time in Patent Office: Days
• US Class Current: 250/234
• CPC Class Codes: G02B 26/085 the reflecting means being moved or deformed by electromagnetic means
• CPC Class Codes: G02B 26/0858 the reflecting means being moved or deformed by piezoelectric means
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129

Abstract

A MEMS oscillator, such as a MEMS scanner, has an improved and simplified drive scheme and structure. Drive impulses may be transmitted to an oscillating mass via torque through the support arms. For multi-axis oscillators drive signals for two or more axes may be superimposed by a driver circuit and transmitted to the MEMS oscillator. The oscillator responds in each axis according to its resonance frequency in that axis. The oscillator may be driven resonantly in some or all axes. Improved load distribution results in reduced deformation. A simplified structure offers multi-axis oscillation using a single moving body. Another structure directly drives a plurality of moving bodies. Another structure eliminates actuators from one or more moving bodies, those bodies being driven by their support arms.

Claims

1. A method for driving a MEMS scanner, comprising the steps of:

generating a single drive signal that includes frequency components at first and second frequencies; and

transmitting the single drive signal to a MEMS scanner having resonant responses at the first and second frequencies;

whereby the MEMS scanner responds with a first periodic motion at the first frequency and a second periodic motion at the second frequency.

2. The method for driving a MEMS scanner of claim 1;

wherein the first frequency is a resonance frequency of the MEMS oscillator in a first axis.

3. The method for driving a MEMS scanner of claim 2, wherein the first frequency is not a resonance frequency of the MEMS oscillator in a second axis.

4. The method for driving a MEMS scanner of claim 3;

wherein the second frequency is a frame rate.

5. The method for driving a MEMS scanner of claim 4;

wherein the step of generating a drive signal includes generating a ramp waveform at the second frequency.

6. The method for driving a MEMS scanner of claim 2;

wherein the second frequency is a resonance frequency of the MEMS scanner in a second axis.

7. The method for driving a MEMS scanner of claim 1;

further comprising the step of receiving a position signal from the MEMS scanner.

8. The method of driving a MEMS scanner of claim 7;

further comprising the step of modifying the drive signal to achieve a desired motion in at least one axis.

9. The method of driving a MEMS scanner of claim 1;

wherein the MEMS scanner is an electromagnetic beam director.

10. The method of driving a MEMS scanner of claim 9;

wherein the MEMS scanner is an electromagnetic beam deflector.

11. The method of driving a MEMS scanner of claim 1;

wherein the drive signal includes multiplexed first and second frequencies.

12. The method of driving a MEMS scanner of claim 11;

wherein the drive signal is separated into frequency components by a resonant response of the MEMS scanner.

13. A MEMS oscillator, comprising:

a body;

a torsion member coupled to the body;

a suspension coupled to the torsion member; and

an oscillator body coupled to the suspension at a plurality of locations.

14. The MEMS oscillator of claim 13;

wherein the oscillator body further includes a reflective surface.

15. The MEMS oscillator of claim 14;

wherein the suspension couples to the oscillator body to improve dynamic flatness of the reflective surface.

16. The MEMS oscillator of claim 13;

wherein the body includes a stationary frame for mounting the MEMS oscillator.

17. The MEMS oscillator of claim 13;

wherein the body includes a moveable gimbal.

18. The MEMS oscillator of claim 13;

wherein the torsion member includes two torsion arms.

19. The MEMS oscillator of claim 18;

wherein each of the two torsion arms is coupled to the oscillator body through a suspension.

20. The MEMS oscillator of claim 13;

wherein the torsion member allows the oscillator body to rotate substantially about only one axis.

21. The MEMS oscillator of claim 13;

wherein the torsion member allows the oscillator body to rotate about two axes.

22. The MEMS oscillator of claim 13;

wherein the suspension further comprises;

a central attachment point to the torsion member;

a beam extending transversally from the central attachment point; and

at least two laterally displaced attachment points to the oscillator body, the laterally displaced attachment points extending from the beam to the oscillator body.

23. The MEMS oscillator of claim 22;

wherein the suspension further includes a central attachment point to the oscillator body, the attachment to the oscillator body being lower in cross sectional area than the torsion arm.

24. The MEMS oscillator of claim 22;

wherein the beam extends laterally for a distance substantially equal to the lateral extent of the oscillator body.

25. The MEMS oscillator of claim 22;

wherein the beam extends to substantially surround the oscillator body.

26. A MEMS oscillator, comprising:

a frame;

a first set of support arms coupled to the frame;

a gimbal coupled to the first set of support arms;

an actuator positioned to drive the gimbal to rotate around an axis defined by the first set of support arms;

a second set of support arms coupled to the gimbal; and

an oscillating body coupled to the second set of support arms to receive a drive impulse through the second set of support arms from the gimbal so as to be driven to oscillate around an axis defined by the second set of support arms.

27. The MEMS oscillator of claim 26, wherein;

the oscillating body is coupled to receive drive impulses at its resonance frequency through the second set of support arms; and

the oscillating body is positioned to oscillate at its resonance frequency.

28. The MEMS oscillator of claim 26, wherein the actuator is positioned to directly drive the gimbal.

29. The MEMS oscillator of claim 26, wherein the actuator is a moving coil magnetic actuator.

30. The MEMS oscillator of claim 26, wherein the actuator is a moving magnet magnetic actuator.

31. The MEMS oscillator of claim 26, wherein the actuator is an electrocapacitive actuator.

32. The MEMS oscillator of claim 26, wherein the first set of support arms comprises two torsion arms.

33. The MEMS oscillator of claim 26, wherein the second set of support arms comprises two torsion arms.

34. The MEMS oscillator of claim 33, wherein the second set of support arms are coupled to the oscillator body through at least one suspension element.

35. The MEMS oscillator of claim 26, wherein at least one of the first set of support arms and the second set of support arms is a single cantilevered arm.

36. The MEMS oscillator of claim 26, wherein the axis of rotation defined by the second set of support arms is transverse to the axis of rotation defined by the first set of support arms.

37. The MEMS oscillator of claim 36, wherein the axis of rotation defined by the second set of support arms is substantially at a right angle to the axis of rotation defined by the first set of support arms.

38. The MEMS oscillator of claim 26, wherein the oscillating body further comprises:

a second gimbal;

a third set of support arms coupled to the second gimbal;

a second oscillating body coupled to the third set of support arms to receive a drive impulse through the third set of support arms from the second gimbal so as to be driven to oscillate around an axis defined by the third set of support arms.

39. The MEMS oscillator of claim 26, wherein the oscillating body further includes a mirror positioned to receive a beam of light and deflect it across a field of view.

40. A MEMS scanner, comprising:

a frame;

a scan plate coupled to the frame, the scan plate being able to rotate around at least two axes of rotation;

one or more actuators coupled to the scan plate; and

two or more drive signal lines coupled to the one or more actuators, the number of drive signal lines being less than twice the number of axes of rotation;

whereby rotation of the scan plate around at least one of the axes of rotation is driven through a pair of drive signal lines that also carries a signal for driving the scan plate to rotate around at least a second axis of rotation.

41. The MEMS scanner of claim 40, wherein the number of actuators is less than the number of axes of rotation.

42. The MEMS scanner of claim 41, wherein the scan plate comprises a single body coupled to the frame by a pair of arms that allow rotation in a plurality of axes.

43. The MEMS scanner of claim 42, wherein the one or more actuators consists of a single actuator.

44. The MEMS scanner of claim 41, wherein the scan plate further comprises:

a gimbal coupled to rotate around a first axis;

a pair of torsion arms coupled to the gimbal; and

an inner scan plate coupled to the pair of torsion arms and allowed to oscillate around a second axis by the pair of torsion arms;

whereby the inner scan plate receives a drive signal through torque transmitted from the gimbal through the pair of torsion arms.

45. The MEMS scanner of claim 41, wherein the scan plate further comprises:

a gimbal coupled to rotate around a first axis;

a pair of torsion arms coupled to the gimbal; and

an inner scan plate coupled to the pair of torsion arms and allowed to rotate around a second axis by the pair of torsion arms;

whereby the gimbal receives a drive signal through torque transmitted from the inner scan plate through the pair of torsion arms.

46. The MEMS scanner of claim 40, wherein:

the one or more actuators includes a plurality of actuators wired in series;

the scan plate is characterized by a resonance frequency range and mechanical amplification factor in at least one axis of rotation; and

at least one of the plurality of actuators is responsive to a drive signal having a frequency component corresponding to the resonance frequency range of the scan plate.

47. A MEMS device, comprising:

an inner plate having a principal oscillatory mode at a first frequency;

an outer plate having a secondary oscillatory mode at the first frequency; and

a coupling between the inner plate and the outer plate selected to couple the first frequency secondary oscillatory mode of the outer plate to the first frequency principal oscillatory mode of the inner plate.

48. The MEMS device of claim 47, wherein the principal oscillatory mode of the inner plate includes rotation about an axis defined by the coupling.

49. The MEMS device of claim 48, further including a mirror surface on the inner plate.

50. The MEMS device of claim 48, wherein the outer plate includes a gimbal structure.

51. The MEMS device of claim 48, wherein the outer plate includes an anchor structure.

52. The MEMS device of claim 47, wherein the coupling includes a post.

53. The MEMS device of claim 47, wherein the coupling includes a bending flexure.

54. The MEMS device of claim 47, wherein the coupling includes at least one torsion arm.

55. The MEMS device of claim 47, where the coupling includes a suspension to distribute the coupled first frequency oscillatory force to a plurality of locations on the inner plate.

56. The MEMS device of claim 47, further comprising an actuator operable to induce the secondary oscillatory response in the outer plate at the first frequency.

57. The MEMS device of claim 47, wherein the outer plate also has a primary oscillatory response at a second frequency.

58. The MEMS device of claim 57, further comprising an actuator operable to induce in the outer plate a secondary oscillatory response at the first frequency and a primary oscillatory response at the second frequency.