Bouncing mode operated scanning micro-mirror

• US 20050036196A1
• Filed: 08/02/2004
• Published: 02/17/2005
• Est. Priority Date: 08/12/2003
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: Terraop Limited
• Inventors: Medina, Moshe, Barnea, Daniel I., Schreiber, David, Krylov, Slava, Ben-Gad, Eliezer
• Granted Patent: US 7,042,613 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A MEMS apparatus for scanning an optical beam comprises a mirror operative to perform a rotational motion to a maximum rotation angle around a mirror rotation axis, and a bouncing mechanism operative to provide a bouncing event and to reverse the rotational motion. The bouncing event provides the mirror with a piecewise linear response to actuation by intrinsically nonlinear electrostatic forces. The bouncing mechanism includes an element chosen to impart an overall nonlinear stiffness to the system and is selected from the group of elements consisting of a bouncer and a pre-curved nonlinear stiffness element.

Claims

1. A tilting micro-mirror device comprising:

a. a substrate;

b. a micro-mirror operative to perform a tilt motion around a tilt axis positioned substantially parallel to said substrate, said tilt motion defined by a tilt range ending in a positive or negative maximum tilt angle; and

c. at least one pair of additional stiffness elements, each element of said pair positioned on opposite sides of said tilt axis and operative to couple to said micro-mirror when said mirror reaches said positive or negative maximum tilt angle, said coupling providing an essentially piecewise linear mirror motion.

2. The tilting micro-mirror device of claim 1, further comprising an actuator operative to provide said tilt motion.

3. The tilting micro-mirror device of claim 2, wherein said at least one pair of additional stiffness elements are connected to an element selected from the group consisting of said mirror and a torsion beam attached to said mirror.

4. The tilting micro-mirror device of claim 2, wherein said at least one pair of additional stiffness elements are connected to said substrate.

5. The tilting micro-mirror device of claim 2, wherein each of said at least one pair of additional stiffness elements are selected from the group consisting of a cantilever, a strip and a beam.

6. The tilting micro-mirror device of claim 2, wherein each element of said at least one pair of additional stiffness elements includes two or more additional elements with different stiffnesses.

7. The tilting micro-mirror device of claim 2, wherein said actuator is selected from the group consisting of a parallel plate electrostatic actuator, a planar comb drive actuator and a vertical comb drive actuator.

8. The tilting micro-mirror device of claim 1, wherein said substrate includes a silicon on insulator (SOI) substrate having an active layer, and wherein said mirror is fabricated in said active layer.

9. The tilting micro-mirror device of claim 9, wherein said SOI substrate includes an SOI substrate bonded to a regular silicon substrate.

10. The tilting micro-mirror device of claim 9, wherein said SOI substrate includes a double-active-layer SOI substrate.

11. A tilting micro-mirror device comprising:

a. a substrate;

b. a micro-mirror operative to perform a tilt motion around a tilt axis positioned substantially parallel to said substrate, said tilt motion defined by a tilt range ending in a positive or negative maximum tilt angle; and

c. at least one pair of pre-curved nonlinear stiffness elements having each two ends, each of said pre-curved elements connected at one of its ends to said micro-mirror and at the other of its ends to said substrate, whereby each said pair is operative to impart said tilt motion an essentially piecewise linear motion characteristic.

12. The tilting micro-mirror device of claim 11, further comprising an actuator operative to provide said tilt motion.

13. The tilting micro-mirror device of claim 12, wherein each element of a said at least one pair of pre-curved nonlinear stiffness elements is selected from the group consisting of a beam and a strip.

14. The tilting micro-mirror device of claim 12, wherein said actuator is selected from the group consisting of a planar comb drive actuator and a vertical comb drive actuator.

15. The tilting micro-mirror device of claim 12, wherein said substrate includes a silicon on insulator (SOI) substrate having an active layer, and wherein said mirror is fabricated in said active layer.

16. The tilting micro-mirror device of claim 15, wherein said SOI substrate includes an SOI substrate bonded to a regular silicon substrate.

17. The tilting micro-mirror device of claim 15, wherein said SOI substrate includes a double-active-layer SOI substrate.

18. The tilting micro-mirror device of claim 11, wherein each said at least one pair of pre-curved elements is selected from the group consisting of a pair of S-shape elements, a pair of C-shape elements, a pair of V-shape elements and a pair of Z-shape elements.

19. A MEMS apparatus for scanning an optical beam comprising:

a. a mirror operative to perform a rotational motion to a maximum rotation angle around a mirror rotation axis; and

b. a bouncing mechanism operative to provide a bouncing event and to reverse said rotational motion;

whereby said bouncing event provides said mirror with a piecewise linear response to actuation by intrinsically nonlinear forces.

20. The MEMS apparatus for scanning an optical beam of claim 19, further comprising an actuator operative to provide said actuation, said actuator connected to a substrate.

21. The MEMS apparatus for scanning an optical beam of claim 19, wherein said bouncing mechanism includes at least one pair of additional stiffness elements, located on opposite sides of said rotation axis, each said nonlinear stiffness element operative to provide one said bouncing event.

22. The MEMS apparatus for scanning an optical beam of claim 21, wherein said at least one pair of additional stiffness elements is connected to an element selected from the group consisting of said mirror and a torsion beam attached to said mirror.

23. The MEMS apparatus for scanning an optical beam of claim 20, further comprising a substrate, wherein said at least one pair of additional stiffness elements is connected to said substrate.

24. The MEMS apparatus for scanning an optical beam of claim 21, wherein each of said additional stiffness elements is selected form the group consisting of a cantilever, a spring and a beam.

25. The MEMS apparatus for scanning an optical beam of claim 20, wherein said bouncing mechanism includes at least one pair of pre-curved nonlinear stiffness elements, each said pre-curved element having two ends, each said pre-curved element connected at one said end to said mirror and an another said end to said actuator.

26. The MEMS apparatus for scanning an optical beam of claim 20, wherein said actuator is selected from the group consisting of a planar comb drive actuator and a vertical comb drive actuator.

27. The MEMS apparatus for scanning an optical beam of claim 25, wherein each said at least one pair of pre-curved elements is selected from the group consisting of a pair of S-shape elements, a pair of C-shape elements, a pair of V-shape elements and a pair of Z-shape elements.

28. The MEMS apparatus for scanning an optical beam of claim 20, wherein said substrate includes a silicon on insulator (SOI) substrate having an active layer, and wherein said mirror is fabricated in said active layer.

29. The MEMS apparatus for scanning an optical beam of claim 28, wherein said SOI substrate includes a double-active-layer SOI substrate.

30. The MEMS apparatus for scanning an optical beam of claim 28, wherein said SOI substrate includes an SOI substrate bonded to a regular Si substrate.

31. A method for scanning an optical beam using a MEMS mirror comprising the steps of:

a. providing a mirror operative to perform a rotational motion to a maximum rotation angle around a mirror rotation axis; and

b. providing a bouncing mechanism operative to facilitate a bouncing event and to reverse said rotational motion;

whereby said bouncing event provides said mirror with a piecewise linear response to actuation by intrinsically nonlinear forces.

32. The method of claim 31, further comprising the steps of

c. providing a substrate in which said mirror is fabricated in;

and

d. providing an actuator operative to actuate said mirror to achieve said rotation.

33. The method of claim 32, wherein said step of providing a bouncing mechanism includes providing at least one pair of additional stiffness elements, located on opposite sides of said rotation axis, each said additional stiffness element operative to provide one said bouncing event when said mirror reaches said maximum rotation angle.

34. The method of claim 33, wherein said providing of at least one pair of additional stiffness elements includes providing at least one pair of bouncers connected to said mirror.

35. The method of claim 33, wherein said providing of at least one pair of additional stiffness elements includes providing at least one pair of bouncers connected to said substrate.

36. The method of claim 33, wherein said providing at least one pair of additional stiffness elements includes providing at least one pair of elements selected from the group of a cantilever, a spring and a beam.

37. The method of claim 32, wherein said step of providing an actuator includes providing an actuator selected from the group consisting of a parallel plate electrostatic actuator, a planar comb drive actuator and a vertical comb drive actuator.

38. The method of claim 32, wherein said step of providing a bouncing mechanism includes providing at least one pair of nonlinear stiffness elements at least one pair of pre-curved nonlinear stiffness elements having each two ends, each of said pre-curved elements connected at one of its ends to said mirror and at the other of its ends to said substrate.

39. The method of claim 38, wherein said step of providing at least one pair of pre-curved nonlinear stiffness elements includes providing at least one pair of pre-curved elements is selected from the group consisting of a pair of S-shape elements, a pair of C-shape elements, a pair of V-shape elements and a pair of Z-shape elements.

40. The method of claim 32, wherein said step of providing a substrate in which said mirror is fabricated in includes providing a silicon on insulator (SOI) substrate having an active layer.

41. The method of claim 32, wherein said step of providing an SOI substrate having an active layer includes providing a double-active-layer SOI substrate.

42. The method of claim 32, wherein said step of providing an SOI substrate having an active layer includes providing an SOI substrate bonded to a regular silicon substrate.