Optical scanning using vibratory diffraction gratings

• US 20050156481A1
• Filed: 12/23/2004
• Published: 07/21/2005
• Est. Priority Date: 01/20/2004
• Status: Active Grant

• Current Assignee: National University of Singapore
• Original Assignee: National University of Singapore
• Inventors: Zhou, Guangya, Vj, Logeeswaran, Chau, Fook Siong
• Granted Patent: US 7,542,188 B2
• Time in Patent Office: Days
• US Class Current: 310/309
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B81B 2201/033 Comb drives
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2203/0109 Bridges
• CPC Class Codes: B81B 2203/056 Rotation in a plane parallel to the substrate
• CPC Class Codes: B81B 3/0062 Devices moving in two or more dimensions, i.e. having special features which allow movement in more than one dimension
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 26/106 having diffraction gratings as scanning elements, e.g. holographic scanners holographic optical elements G02B5/32, holography G03H
• CPC Class Codes: H02N 1/008 Laterally driven motors, e.g. of the comb-drive type

Abstract

An optical scanning apparatus includes an in-plane vibratory mass platform having at least one diffraction grating formed thereon as the scanning element, at least one flexure structure that connects the mass platform to at least one fixed support, and at least one driving actuator that drives the mass platform into an in-plane vibratory motion which can be rotational and/or translational. The apparatus may also be formed by a mass platform having at least one diffraction grating formed thereon as the scanning element, at least one driving actuator connected to the mass platform through at least one flexure structure. The driving actuator drives the mass platform into an in-plane vibratory motion.

Claims

1. A vibratory mechanical structure, comprising:

a mass platform;

at least one support structure connected to the mass platform through at least one flexural structure;

at least one diffraction grating patterned on the mass platform; and

at least one driving actuator.

2. The structure of claim 1, wherein the mass platform, is driven in an in-plane motion that is at least one of rotational or translational motion, and said in-plane motion can be combined with out-of-plane motion that is at least one of rotational or translational motion.

3. The structure of claim 1, wherein the mass platform, is driven in an in-plane motion that is at least one of rotational or translational motion, said in-plane motion being in combination with out-of-plane motion that is at least one of rotational or translational motion, and the structure is used for multi-dimensional scanning.

4. The structure of claim 1, wherein the mass platform, the flexure structure and driving actuator need not be formed on the same substrate and their center-of-mass are not confined to lie on the same plane.

5. The structure of claim 1, wherein the diffraction grating can be orientated at any angle with respect to the mass platform.

6. The structure of claim 1, wherein an excitation force produced by the at least one driving actuator is applied directly to the mass platform.

7. The structure of claim 1, wherein an excitation force produced by the at least one driving actuator is applied directly to the flexural structure.

8. The structure of claim 1, wherein an excitation force produced by the at least one driving actuator is applied directly to the support structure.

9. The structure of claim 1, wherein the support structure can be fixed or movable.

10. The structure of claim 1, wherein the mass platform and the flexure structure can take any geometrical shape or topology.

11. The structure of claim 1, wherein the driving actuator comprises a comb drive having an interdigitated finger structure having fixed fingers and movable fingers.

12. The structure of claim 11, wherein the movable fingers connect to the mass platform.

13. The structure of claim 11, wherein the fixed fingers comprise a fixed electrode connected to a substrate.

14. The structure of claim 11, wherein the comb drive is a circular comb drive.

15. The structure of claim 1, further comprising a folded beam suspension connected to the support structure.

16. The structure of claim 15, wherein the folded beam suspension is connected to a substrate.

17. The structure of claim 1, wherein the flexural structure is a first flexural structure connected to the mass platform, and the first flexural structure transversely connects to a second flexural structure, and the second flexural structure has two ends that are connected to the support structure.

18. A vibratory-mechanical structure, comprising:

a mass platform;

a first support connected to the mass platform through a first flexural structure;

a second support connected to the mass platform through a second flexural structure, the second support and second flexural structure attaching to the mass platform at a 180°

angle to the first support and first flexural structure;

a first comb drive attached to the mass platform at a 90°

angle from the first support and flexural structure; and

a second comb drive attached to the mass platform at a 270°

angle from the first support and flexural structure.

19. The structure of claim 18, wherein each comb drive comprises an interdigitated finger structure having fixed fingers and movable fingers.

20. The structure of claim 19, wherein the movable fingers of each comb drive connect to the mass platform.

21. The structure of claim 19, wherein the fixed fingers of each comb drive are a fixed electrode connected to a substrate.

22. The structure of claim 18, wherein the mass platform contains a diffraction grating.

23. The structure of claim 18, wherein each comb drive is a circular comb drive.

24. The structure of claim 18, wherein the platform is circular.

25. A vibratory-mechanical structure, comprising:

a mass platform;

a support connected to the mass platform through a flexural structure; and

a comb drive having a movable electrode having a movable electrode formed on the flexural structure and at least one fixed electrode attached to a substrate.

26. The structure of claim 25, wherein the comb drive has an interdigitated finger structure having fixed fingers attached to the fixed electrode and movable fingers attached to the movable electrode, and the fingers are at a right angle to the flexural beam.

27. The structure of claim 25, wherein the mass platform contains a diffraction grating.

28. A vibratory-mechanical structure, comprising:

a mass platform; and

a comb drive resonator connected to the mass platform through a flexural structure.

29. The structure of claim 28, wherein the comb drive resonator comprises:

a support structure attached to the flexural structure;

at least one folded beam suspension attached to the support structure; and

first and second comb drives attached to opposite ends of the support structure.

30. The structure of claim 29, wherein each comb drive has an interdigitated finger structure having fixed fingers attached to a fixed electrode and movable fingers attached to the support structure.

31. The structure of claim 29, wherein the support structure attaches to the flexural structure at a right angle.

32. The structure of claim 29, wherein the folded beam suspension has flexure elements aligned parallel to the flexural structure.

33. The structure of claim 29, wherein the folded beam suspension is fixed to a substrate.

34. A vibratory-mechanical structure, comprising:

a mass platform; and

a parallel-plate electrostatic actuator connected to the mass platform through a flexural structure.

35. The structure of claim 34, wherein the parallel-plate electrostatic actuator comprises:

a support structure attached to the flexural structure;

at least one folded beam suspension attached to the support structure; and

first and second parallel-plate actuators attached to opposite ends of the support structure.

36. The structure of claim 35, wherein each parallel plate actuator is fixed to a substrate.

37. The structure of claim 35, wherein the support structure attaches to the flexural structure at a right angle.

38. The structure of claim 35, wherein the folded beam suspension has flexure elements aligned parallel to the flexural structure.

39. The structure of claim 35, wherein the folded beam suspension is fixed to a substrate.

40. A vibratory-mechanical structure, comprising:

a mass platform;

a first comb drive resonator connected to the mass platform through a first flexural structure; and

a second comb drive resonator connected to the mass platform through a second flexural structure, wherein the second flexural structure is connected to the platform at a 180°

angle to the first flexural structure.

41. The structure of claim 40, wherein the each comb drive resonator comprises:

a support structure attached to the mass platform using a flexural suspension, and the flexural suspension includes the flexural structure and a transverse structure placed in a T-like pattern;

at least one folded beam suspension attached to the support structure; and

first and second comb drives attached to opposite ends of the support structure.

42. The structure of claim 41, wherein each comb drive has an interdigitated finger structure having fixed fingers attached to a fixed electrode and movable fingers attached to the support structure.

43. The structure of claim 40, wherein the mass platform contains a diffraction grating.

44. A vibratory-mechanical structure, comprising:

a mass platform;

a first comb drive resonator connected to the mass platform through a first flexural structure;

a second comb drive resonator connected to the mass platform through a second flexural structure, wherein the second flexural structure is connected to the mass platform at a 120°

angle to the first flexural structure; and

a third comb drive resonator connected to the mass platform through a third flexural structure, wherein the third flexural structure is connected to the mass platform at a 240°

angle to the first flexural structure.

45. The structure of claim 44, wherein the each comb drive resonator comprises:

a support structure attached to the mass platform using a flexural suspension, and the flexural suspension includes the flexural structure and a transverse structure placed in a T-shape pattern;

at least one folded beam suspension attached to the support structure; and

first and second comb drives attached to opposite ends of the support structure.

46. The structure of claim 45, wherein each comb drive has an interdigitated finger structure having fixed fingers attached to a fixed electrode and movable fingers attached to the support structure.

47. The structure of claim 45, wherein the mass platform contains a diffraction grating.

48. A method for forming a vibratory-mechanical diffraction grating, comprising:

providing a silicon-on-insulator wafer;

forming a photoresist layer over the wafer;

forming a grating pattern in the photoresist;

transferring the grating pattern to the wafer using RIE;

forming a second layer of photoresist over the wafer;

forming a first pattern in the photoresist followed by DRIE etching;

forming a second patterned under the wafer followed by DRIE etching; and

etching exposed SiO₂ to release the grating'"'"'s structure.

49. The method of claim 48, wherein the first pattern includes a mass platform, suspension flexurals, support structures and driving actuators.

50. The method of claim 48, wherein the silicon-on-insulator wafer comprises a handle wafer of 450-600 μ

m thickness, an oxide thickness of 0.2-2.0 μ

m, and a device layer of 10-50 μ

m.