Three-dimensional microelectromechanical tilting platform operated by gear-driven racks

• US 6,960,849 B1
• Filed: 03/31/2003
• Issued: 11/01/2005
• Est. Priority Date: 03/31/2003
• Status: Active Grant

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Habbit, Robert D. Jr., Klody, Kelly A.
• Primary Examiner(s): TAMAI, KARL I
• Application Number:
  US10/404,780
• Time in Patent Office: 946 Days
• Field of Search: 310/309, 310/40.MM, 385/18, 359/290, 359/291, 359/223, 359/226, 74/29, 74/76, 257/425, 257/420, 605/27
• US Class Current: 310/40.0MM
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 6/3518 the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833
• CPC Class Codes: G02B 6/3566 involving bending a beam, e.g. with cantilever
• CPC Class Codes: G02B 6/3576 Temperature or heat actuation thermal forces controlling reflecting elements in general G02B26/0866; thermo-optic devices G02F1/0147
• CPC Class Codes: G02B 6/3584 constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching MEMS per se B81B, B81C
• CPC Class Codes: G02B 6/359 of the position of the moving element itself during switching, i.e. without monitoring the switched beams

Abstract

A microelectromechanical (MEM) tiltable-platform apparatus is disclosed which utilizes a light-reflective platform (i.e. a micromirror) which is supported above a substrate by flexures which can be bent upwards to tilt the platform in any direction over an angle of generally ±10 degrees using a gear-driven rack attached to each flexure. Each rack is driven by a rotary microengine (i.e. a micromotor); and an optional thermal actuator can be used in combination with each microengine for initially an initial uplifting of the platform away from the substrate. The MEM apparatus has applications for optical switching (e.g. between a pair of optical fibers) or for optical beam scanning.

Claims

1. A microelectromechanical tiltable-platform apparatus, comprising:

(a) a substrate;

(b) a platform tiltably supported above the substrate by a plurality of flexures, with each flexure being connected to the platform proximate to an outer edge thereof through a compliant member;

(c) at least three gear-driven racks located on the substrate and moveable in the plane of the substrate, with one of the racks being connected to an end of each flexure to tilt the platform in response to movement of at least one of the racks by a rotary microengine located on the substrate; and

(d) a thermal actuator operatively connected to an end of each rack opposite the flexure to act in combination with the rack to initially uplift the platform above the substrate.

2. The apparatus of claim 1 wherein the substrate comprises silicon.

3. The apparatus of claim 1 wherein the platform comprises a plurality of stacked and interconnected layers of polycrystalline silicon.

4. The apparatus of claim 3 wherein at least one of the layers of polycrystalline silicon is patterned to form a lattice structure.

5. The apparatus of claim 4 wherein the lattice structure comprises a honeycomb structure or a rectangular grid structure.

6. The apparatus of claim 5 wherein the lattice structure further includes an annulus located beneath the outer edge of the platform.

7. The apparatus of claim 1 wherein each rotary microengine comprises a pair of electrostatic comb actuators operatively connected to drive an output gear.

8. The apparatus of claim 7 wherein the output gear is operably connected to move the rack through a reduction gear train.

9. The apparatus of claim 8 further including an idler gear located on a side of each rack opposite the reduction gear train.

10. The apparatus of claim 1 wherein the platform is tiltable over an angle of ±

10 degrees in any direction with respect to the plane of the substrate.

11. The apparatus of claim 1 wherein the platform is tiltable in response to an actuation voltage applied to at least one of the rotary microengines, with the platform remaining in a fixed position upon removal of the actuation voltage.

12. The apparatus of claim 1 wherein a surface of the platform includes a mirror coating.

13. The apparatus of claim 1 wherein the plurality of gear-driven racks comprises three or four racks.

14. The apparatus of claim 1 further comprising a plurality of fuses anchoring the platform to the substrate during fabrication thereof, with each fuse being electrically or mechanically severable to release the platform for movement.

15. A microelectromechanical tiltable-platform apparatus, comprising:

(a) a substrate;

(b) a platform tiltably supported above the substrate by a plurality of flexures, with each flexure being connected to the platform proximate to an outer edge thereof through a compliant member;

(c) a plurality of gear-driven racks located on the substrate and moveable in the plane of the substrate, with one end of each rack being connected to one of the flexures to tilt the platform in response to movement of the rack by a rotary microengine located on the substrate; and

(d) a thermal actuator operatively connected to another end of each rack to act in combination with the rack to initially bend each flexure upward thereby uplifting the platform above the substrate.

16. A microelectromechanical tiltable-platform apparatus, comprising:

(a) a substrate;

(b) a platform tiltably supported above the substrate by a plurality of flexures, with each flexure being connected to the platform proximate to an outer edge thereof through a compliant member;

(c) a plurality of gear-driven racks located on the substrate and moveable in the plane of the substrate, with one of the racks being connected to an end of each flexure to tilt the platform in response to movement of at least one of the racks by a rotary microengine located on the substrate; and

(d) at least one pawl to engage each rack to prevent the platform from contacting the substrate.

17. A microelectromechanical tiltable-platform apparatus for redirecting an incident light beam, comprising:

(a) a tiltable mirror supported above a substrate for reflecting the incident light beam;

(b) three or four gear-driven racks located on the substrate and spaced about an outer edge of the mirror, with each gear-driven rack being operatively connected to the outer edge of the mirror through a flexure, and with each gear-driven rack further comprising a rotary microengine operatively connected to move the rack in the plane of the substrate towards the mirror to raise the outer edge thereby tilting the mirror; and

(c) a thermal actuator operatively connected to an end of each rack to act in combination with the rotary microengine for initially uplifting the mirror away from the substrate.

18. The apparatus of claim 17 wherein the substrate comprises silicon.

19. The apparatus of claim 17 wherein the tiltable mirror comprises a plurality of stacked and interconnected layers of polycrystalline silicon.

20. The apparatus of claim 19 wherein at least one of the layers of polycrystalline silicon is patterned to form a lattice structure.

21. The apparatus of claim 20 wherein the lattice structure comprises a honeycomb structure or a rectangular grid structure.

22. The apparatus of claim 17 wherein the rotary microengine is operatively connected to move the rack through a reduction gear train.

23. The apparatus of claim 17 wherein each thermal actuator comprises an elongate bent beam anchored to the substrate at each end thereof, with the beam being further bowed in response to heating by an applied electrical current.

24. The apparatus of claim 17 further including a pawl for engaging an end of each rack to prevent the mirror from contacting the substrate.