GIMBALED SCANNING MICRO-MIRROR APPARATUS

• US 20110228367A1
• Filed: 12/02/2010
• Published: 09/22/2011
• Est. Priority Date: 06/02/2008
• Status: Active Grant

• Current Assignee: Maradin Ltd.
• Original Assignee: Maradin Technologies Ltd.
• Inventors: LUBIANIKER, Yoram, ERLICH, Raviv, NAFTALI, Matan, BARAM, Adi
• Granted Patent: US 8,810,879 B2
• Time in Patent Office: Days
• US Class Current: 359/199.2
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 26/085 the reflecting means being moved or deformed by electromagnetic means
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence
• CPC Class Codes: H01F 2007/068 using printed circuit coils
• CPC Class Codes: H02K 33/16 with polarised armatures moving in alternate directions by reversal or energisation of a single coil system
• CPC Class Codes: H02N 1/008 Laterally driven motors, e.g. of the comb-drive type
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

Provided is a Micro-Electro-Mechanical Systems (MEMS) device for actuating a gimbaled element, the device including a symmetric electromagnetic actuator for actuating one degree of freedom (DOF) and a symmetric electrostatic actuator for actuating the second degree of freedom.

Claims

1. A micro-electro-mechanical device for actuating a gimbaled element for two-dimensional optical scanning, the device comprising:

an electromagnetically activated gimbal receiving, and operative in accordance with, a step-wave shaped input signal;

an electrostatically actuated resonant mirror mounted on the gimbal and defining two degrees of freedom of motion for the mirror; and

a feedback control loop operative to generate feedback data quantifying motion of the mirror and to control the two degrees of freedom of motion of the mirror, based on the feedback data.

2. The device according to claim 1, comprising:

an electromagnetic actuator for providing a first angular degree of freedom (DOF) of rotation of the mirror about a first axis, by actuating the gimbal; and

an electrostatic actuator for providing a second angular degree of freedom of rotation of the mirror about a second axis which does not coincide with the first axis by actuating the mirror.

12. The device of claim 2, wherein the electromagnetic actuator has a symmetric structure configured to ensure that actuating forces produced by the electromagnetic actuator create only rotational motion of the first degree of freedom about the horizontal axis.

13. The device of claim 12, wherein the electromagnetic actuator, excites negligible residual actuation force on the second degree of freedom.

14. The device of claim 2, wherein the electrostatic actuator uses electrostatic fringing fields to create an actuation force.

15. The device of claim 14, wherein the electrostatic actuator has a symmetric structure, configured to ensure that actuating forces produced by the electrostatic actuator create only a rotational movement of the second degree of freedom about the horizontal axis.

16. The device of claim 15, wherein the electrostatic actuator excites negligible residual actuation force on the first degree of freedom.

17. The device of claim 2, wherein the electrostatic actuator comprises a structural portion having two sides, and wherein there is no electrical potential difference between the two sides of the structural portion of the electrostatic actuator.

18. The device of claim 2, wherein the electromagnetic actuator comprises:

(a) at least one external fixed electromagnet coil; and

(b) an internal rotating magnet.

19. The device of claim 18, wherein the rotating magnet is affixed to the vertical axis and actuated by the electromagnet coil.

20. The device of claim 18, wherein the at least one electromagnetic coil comprises at least a pair of electromagnetic coils disposed on both sides of the vertical axis.

21. The device of claim 2, wherein the electrostatic actuator actuates the second degree of freedom in a horizontal scan direction.

22. The device of claim 2, wherein the electromagnetic actuator actuates the first degree of freedom in a vertical scan direction.

23. The device of claim 12, wherein the electromagnetic actuator has a linear electromechanical response.

24. The device of claim 14, wherein the electrostatic actuator has a sinusoidal electromechanical response.

25. The device of claim 2, wherein the electrostatic actuator comprises a frequency sensor with high signal to noise ratio.

42. A system according to claim 1, wherein the mirror and the gimbal define first and second elements at least one of which is free to move relative to the other, the first element comprising first and second layers of material having an electrical potential difference therebetween.

43. The system according to claim 42, wherein the second and third layers of material are held at the same electrical potential, such that the electrical potential difference between the first and second elements is created by a fringe field effect.

3. A method for manufacturing first and second elements with relative electrostatically actuated motion therebetween, the method including:

providing first and second elements at least one of which is free to move relative to the other, the first element comprising first and second mutually isolated layers of material having an electrical potential difference therebetween, the second element comprising a third layer of material, wherein the second and third layers of material are held at the same electrical potential, such that an electrical potential difference between the first and second elements is created by a fringe field effect.

4. The method according to claim 3, wherein the providing comprises:

depositing an initial layer and generating the second and third layers by separating the initial layer into disjointed planar portions.

5. The method according to claim 4, comprising depositing the first layer onto the second layer and not onto the third layer.

6. The method according to claim 3, wherein the second and third layers of material comprise silicon layers.

8. The method according to claim 3, wherein at least one of the first and second layers of material comprises a patterned layer of electro-mechanical devices.

9. The method according to claim 8, wherein the electro-mechanical devices comprise MEMS devices.

10. The method according to claim 3, wherein the first element comprises a mirror having a reflective surface, and the first layer of material comprises the reflective surface of the mirror.

11. The method according to claim 3, wherein the second element comprises a gimbal.

7. An electrostatic actuator, comprising:

first and second structural elements formed from a single layer of material and having the same first electrical potential; and

an electrode mounted on and isolated from the first structural element and having a second electrical potential differing from the first electrical potential.

26. A method for micro-electro-mechanically actuating a gimbaled element for two-dimensional optical scanning, comprising:

mounting an electrostatically actuated resonant mirror on an electromagnetically activated gimbal; and

providing a step-wave shaped input signal to the electromagnetically activated gimbal.

44. The method according to claim 26, wherein the mirror rotates about a first axis responsive to actuation of the gimbal, the method also comprising providing an electrostatic actuator causing the mirror to rotate about a second axis which does not coincide with the first axis by actuating the mirror.

45. The method of claim 26, wherein the mounting comprises fabricating the mirror and the gimbal using a 4-mask Silicon-On-Insulator (SOI) fabrication process.

27. Apparatus for generating controlled pivoting motion, the apparatus comprising:

a pivoting structural portion and first and second flexures, the first flexure having first and second ends, the second flexure being formed of a piezo-resistive material and having at least first and second ends, at least one of which is fixed, the first flexure being operative to twist along at least a first axis, the second flexure being configured and oriented to define an elongate projection about a second axis perpendicular to the first axis, wherein the pivoting portion is disposed at and fixed relative to the first end of the first flexure and wherein the second end of the first flexure is attached to the second flexure,

a piezo-resistive response detector operative to detect at least one characteristic of a piezo-resistive response of at least a portion of the second flexure to pivoting motion of the pivoting structural portion; and

a pivoting motion generator operative to generate the pivoting motion based on at least one characteristic of the pivoting motion computed from the at least one characteristic of the piezo-resistive response.

51. The apparatus according to claim 27, wherein the structural portion is at least partly formed of silicon.

52. The apparatus according to claim 27, wherein the structural portion comprises a gimbal apparatus.

53. The apparatus according to claim 52, wherein the structural portion also comprises a mirror apparatus mounted on the gimbal apparatus.

54. The apparatus according to claim 53, wherein the mirror apparatus has toothed edges and the gimbal has toothed edges interlaced with the toothed edges of the mirror apparatus.

28. A method for electro-statically sensing motion of a moving element, comprising:

providing first and second elements at least one of which is free to move relative to the other, the first element comprising first and second layers of material having an electrical potential difference therebetween, the second element including a third layer of material having an electrical potential difference with at least one of the first and second layers;

generating relative motion between the first and second elements; and

measuring the electrical potential difference between the third layer and at least one of the first and second layers.

29. A method for sensing pivoting motion of a pivoting portion of a structural element, comprising:

providing a pivoting structural portion and first and second flexures, the first flexure having first and second ends, the second flexure being formed of a piezo-resistive material and having at least first and second ends, at least one of which is fixed, the first flexure being operative to twist along at least a first axis, the second flexure being configured and oriented to define an elongate projection about a second axis perpendicular to the first axis, wherein the pivoting portion is disposed at and fixed relative to the first end of the first flexure and wherein the second end of the first flexure is attached to the second flexure,

detecting at least one characteristic of a piezo-resistive response of at least a portion of the second flexure to pivoting motion of the pivoting structural portion; and

computing at least one characteristic of the pivoting motion from the at least one characteristic of the piezo-resistive response.

30. The method according to claim 29, wherein the detecting comprises measuring the piezo-resistive response at a location along the second flexure which is removed from the first axis.

31. The method according to claim 29, comprising:

providing a pivoting motion generator operative to generate the pivoting motion; and

controlling the pivoting motion generator using the characteristic of the pivoting motion generated in the computing step.

32. The method according to claim 29, wherein at least one of the flexures is formed of silicon.

33. The method according to claim 32, wherein the silicon comprises single crystal silicon.

34. An oscillating scanning mirror apparatus, comprising:

an oscillating scanning mirror; and

at least one functional element interacting with the scanning mirror and synchronized directly to the scanning mirror.

35. The apparatus according to claim 34, wherein the scanning mirror defines, by its oscillation, a period and a frequency, and wherein the functional element is actuated with a periodicity which is a rational multiple of the period.

36. The apparatus according to claim 34, wherein the at least one functional element comprises a data streaming device operative to stream light characterizing data which characterizes light impinging upon the scanning mirror.

37. The apparatus according to claim 34, wherein the scanning mirror'"'"'s oscillation occurs about a first axis and wherein the scanning mirror also executes a pivoting motion about a second axis different from the first axis and wherein the at least one functional element comprises a device for imparting the pivoting motion to the scanning mirror about the second axis.

38. The apparatus according to claim 34, comprising a frequency sensor operative to sense the frequency.

39. The apparatus according to claim 34, wherein the device for imparting motion comprises a gimbal.

58. The apparatus according to claim 34, wherein the oscillating scanning mirror element comprises a pivoting mirror device pivoting along a first axis.

59. The apparatus according to claim 34, wherein the functional element comprises a gimbal device pivoting along a second axis.

60. The apparatus according to claim 59, wherein the oscillating scanning mirror element comprises a pivoting mirror device mounted on the gimbal device and pivoting along a first axis which does not coincide with the second axis.

61. The apparatus according to claim 34, wherein the functional element comprises a data streaming device.

62. The apparatus according to claim 58, wherein the functional element comprises a light characterizing data streaming device;

the apparatus also comprising a light source generating a light beam impinging upon the mirror device, the light beam having characteristics determined by the light characterizing data.

40. A method for projecting an image, comprising:

scanning an area to distribute light information representing the image throughout the area, using an interlaced schedule and micro-electro-mechanical direct current motor apparatus to impart the interlaced schedule, the motor apparatus being operative to repeatedly impart instances of angular motion to an element, wherein the instances of angular motion are temporally interspersed with a sequence of stationary intervals during which the element is stationary, the motor apparatus comprising a stator, a rotor pivoting about an axis along a route having a length of less than several dozen microns, the rotor comprising a flexure element fixedly associated with the stator, the flexure element comprising a magnetic portion;

the stator comprising a ferro-magnetic core having a curved configuration which is almost closed thereby to define an air-gap closing the curved configuration and having a width exceeding the route length by only a few microns and a conductive coil wrapped around at least a portion of the almost closed curved configuration of the ferro-magnetic core, at least the magnetic portion of the flexure element being disposed within the air-gap, thereby to generate a first magnetic field in the air-gap, an alternating current flowing through the conductive coil thereby to generate a second, alternating magnetic field within the air gap, the magnetic portion being oriented such that the first magnetic field generated thereby in the air-gap, when interacting with the second, alternating magnetic field within the air-gap, generates a moment about the axis.

41. An electro-statically actuated system, comprising:

first and second elements at least one of which is free to move relative to the other, the first element comprising first and second layers of material having an electrical potential difference therebetween, the second element comprising a third layer of material having an electrical potential difference with at least one of the first and second layers.

46. An apparatus for electro-statically sensing motion of a moving element, comprising:

first and second elements at least one of which is free to move relative to the other, the first element comprising first and second isolated layers of material having an electrical potential difference therebetween; and

an apparatus for generating relative motion between the first and second elements and measuring the electrical potential difference.

55. The apparatus according to claim 46, wherein one of the first and second elements comprises a gimbal apparatus.

56. The apparatus according to claim 55, wherein the other one of the first and second elements comprises a mirror apparatus mounted on the gimbal apparatus.

57. The apparatus according to claim 55, wherein the mirror apparatus has toothed edges and the gimbal has toothed edges interlaced with the toothed edges of the mirror apparatus.

63. The apparatus according to claim 46, wherein the first layer and the second element are fabricated from a single structural layer.

47. An actuation method for actuating an active micro-electrical mechanical system, comprising:

providing an active micro-electrical mechanical system comprising at least one functional element and at least one resonating element having a resonance frequency, wherein the at least one functional element is clocked by a clock signal; and

sensing the resonance frequency of the resonating element and setting the clock signal to the resonance frequency.

48. A micro-electro-mechanical direct current motor apparatus to repeatedly impart instances of angular motion to an element, wherein the instances of angular motion are temporally interspersed with a sequence of stationary intervals during which the element is stationary, comprising:

a stator;

a rotor pivoting about an axis along a route having a length of less than several dozen microns, the rotor comprising a flexure element fixedly associated with the stator, the flexure element comprising a magnetic portion;

wherein the stator comprises;

a ferro-magnetic core having a curved configuration which is almost closed thereby to define an air-gap closing the curved configuration and having a width exceeding the route length by only a few microns; and

a conductive coil wrapped around at least a portion of the almost closed curved configuration of the ferro-magnetic core;

and wherein at least the magnetic portion of the flexure element is disposed within the air-gap, to thereby generate a first magnetic field in the air-gap;

and wherein an alternating current flows through the conductive coil to thereby generate a second, alternating magnetic field within the air gap; and

wherein the magnetic portion is oriented such that the first magnetic field generated thereby in the air-gap, when interacting with the second, alternating magnetic field within the air-gap, generates a moment about the axis.

49. The motor apparatus according to claim 48, wherein the rotor comprises a gimbal.

50. The motor apparatus according to claim 49, comprising a mirror mounted on the gimbal.