High fill ratio reflective spatial light modulator with hidden hinge

• US 20040240033A1
• Filed: 05/18/2004
• Published: 12/02/2004
• Est. Priority Date: 06/19/2002
• Status: Active Grant

• Current Assignee: Shaoher X. Pan, Xiao Yang
• Original Assignee: Shaoher X. Pan, Xiao Yang
• Inventors: Yang, Xiao, Pan, Shaoher X.
• Granted Patent: US 6,992,810 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 micro mirror array having a hidden hinge that is useful, for example, in a reflective spatial light modulator. In one embodiment, the micro mirror array includes spacer support walls, a hinge, a mirror plate and a reflective surface on the upper surface of the mirror plate, the reflective surface concealing the hinge and the mirror plate. The micro mirror array fabricated from a single material.

Claims

1. A micro mirror comprising:

a mirror plate having an upper surface and a lower surface;

a hinge connected to the mirror plate for allowing the mirror plate to rotate relative to a longitudinal axis of the hinge; and

a reflective surface on the upper surface of the mirror plate and above a portion of the hinge, the reflective surface having an area greater than an area of the upper surface of the mirror plate.

2. The micro mirror of claim 1, wherein the reflective surface substantially conceals the hinge.

3. The micro mirror of claim 1, wherein the hinge is formed substantially beneath the upper surface of the mirror plate and is substantially concealed by the reflective surface.

4. The micro mirror of claim 1, further comprising a spacer support frame, the hinge connected to the spacer support frame.

5. The micro mirror of claim 4, wherein the hinge has a first arm and a second arm, each arm having two ends, one end the spacer support frame and the other end connected to a connector to the mirror plate.

6. The micro mirror of claim 1, wherein the mirror plate and the hinge are fabricated from a single piece of material.

7. The micro mirror of claim 4, wherein the mirror plate, the hinge and the spacer support frame are fabricated from a single piece of material.

8. The micro mirror of claim 6, wherein the material is single crystal silicon.

9. The micro mirror of claim 1, wherein the hinge is a torsion spring having a width of between about 0.12 microns to about 0.2 microns and a depth of between about 0.2 microns to about 0.3 microns.

10. The micro mirror of claim 1, further comprising a motion stop, the motion stop attached to the lower surface of the mirror plate for stopping rotation of the mirror plate about the longitudinal axis of the hinge beyond a predetermined angle.

11. The micro mirror of claim 4, wherein the spacer support frame includes at least one wall for supporting the mirror plate, the wall having a thickness of about 1 micron or less.

12. The micro mirror of claim 4, further comprising a control substrate connected to the spacer support frame and having an electrode for receiving a voltage, the voltage used to apply a bias between the mirror plate and the electrode to controllably deflect the mirror plate of the micro mirror.

13. The micro mirror of claim 12, wherein the hinge divides the mirror plate into a first part and a second part, such that when the first part of the mirror plate moves toward the control substrate as the mirror rotates about the longitudinal axis defined by the hinge, the second part of the mirror plate moves away from the control substrate.

14. The micro mirror of claim 11, wherein the spacer support frame has four walls positioned orthogonally to support the mirror plate and the hinge and the rotation of the mirror about an axis defined by the hinge.

15. The micro mirror of claim 11, wherein the hinge is parallel to the wall of the spacer support frame.

16. The micro mirror of claim 11, wherein the hinge is diagonally oriented with respect to the spacer support frame.

17. An array of micro mirrors, comprising:

a plurality of mirror plates, a mirror plate having an upper surface and a lower surface;

a plurality of hinges, a hinge coupled to the mirror plate for allowing the mirror plate to rotate relative to the spacer support frame about an axis defined by the hinge; and

a plurality of reflective surfaces, a reflective surface on the upper surface of the mirror plate and above a portion of the hinge, the reflective surface having an area greater than an area of the upper surface of the mirror plate.

18. The array of micro mirrors of claim 17, wherein the reflective surface substantially conceals the hinge.

19. The array of micro mirrors of claim 17, wherein the hinge is formed substantially beneath the upper surface of the mirror plate and is substantially concealed by the reflective surface.

20. The array of micro mirrors of claim 17, further comprising a spacer support frame with walls defining a plurality of cavities, each cavity corresponding to a micro mirror.

21. The array of micro mirrors of claim 20, wherein the mirror plate, the hinge and the spacer support frame are fabricated from a single piece of material.

22. The array of micro mirrors of claim 21, wherein the material is single crystal silicon.

23. The array of micro mirrors of claim 17, further comprising a plurality of motion stops, a motion stop attached to the lower surface of the mirror plate for stopping rotation of the mirror plate relative to the spacer support frame when the mirror plate has rotated to a predetermined angle.

24. The array of claim 20, further comprising a control substrate connected to the spacer support frame and having at least one electrode corresponding to each of the plurality of mirror plates for receiving a voltage, the voltage used to apply a bias between the mirror plate and the electrode to controllably deflect the mirror plate of the micro mirror.

25. The array of claim 24, wherein the hinge divides the mirror plate into a first part and a second part, such that when the first part of the mirror plate moves toward the control substrate as the mirror plate rotates about the axis defined by the hinge, the second part of the mirror plate moves away from the control substrate.

26. The array of claim 24, wherein the control substrate further comprises addressing and control circuitry for selectively applying voltages to the plurality of electrodes to selectively controllably deflect the mirror plates in the array.

27. The array of claim 17, wherein the reflective surfaces in array make up as much as 94.5% of the surface area of the array.

28. An array of a plurality of micro mirrors, comprising:

a first micro mirror comprising

a first mirror plate having a first upper surface and a first lower surface,

a first hinge connected to the first mirror plate for allowing the first mirror plate to rotate relative to a longitudinal axis of the first hinge, and

a first reflective surface on the first upper surface of the first mirror plate and above the first hinge, the first reflective surface having an area greater than an area of the first upper surface of the first mirror plate; and

a second micro mirror comprising

a second mirror plate having a second upper surface and a second lower surface,

a second hinge connected to the second mirror plate for allowing the second mirror plate to rotate relative to a longitudinal axis of the second hinge, and

a second reflective surface on the second upper surface of the second mirror plate and above the second hinge, the second reflective surface having an area greater than an area of the second upper surface of the first mirror plate.

29. The array of a plurality of micro mirrors of claim 28, wherein the first micro mirror and the second micro mirror further comprise a spacer support frame, the first hinge connected to the spacer support frame for the first micro mirror and the second hinge connected to the spacer support frame for the second micro mirror.

30. The array of claim 28, wherein the first and second mirror plates are substantially square in shape.

31. The array of claim 28, wherein the first and second mirror plates are substantially triangular in shape.

32. The array of claim 28, wherein the first and second upper surfaces have an area of approximately 225 square microns.

33. A method of operating a micro mirror array, comprising:

selecting a micro mirror to deflect in the array;

applying a voltage to an electrode corresponding to the selected micro mirror causing the micro mirror to rotate about a hinge, the hinge positioned substantially beneath an upper surface and under a reflective surface of the micro mirror, and permitting light striking the micro mirror to be reflected in a desired direction; and

wherein the micro mirror further has a mirror plate upon which the reflective surface is deposited and a spacer support frame, each of the hinge, mirror plate and spacer support frame are fabricated from a single piece of material.

34. The method of operating a micro mirror array of claim 33, further comprising removing the voltage from the electrode corresponding to the selected micro mirror permitting the micro mirror to return to an unbiased position.

35. The method of operating a micro mirror array of claim 33, further comprising stopping the rotation of the micro mirror about the hinge using a motion stop.

36. A spatial light modulator, comprising:

means for selecting a micro mirror to deflect in an array of micro mirrors;

means for applying a voltage to an electrode corresponding to the selected micro mirror causing the micro mirror to rotate about a hinge, the hinge positioned substantially beneath an upper surface and under a reflective surface of the micro mirror, and permitting light striking the micro mirror to be reflected in a desired direction; and

wherein the micro mirror further has a mirror plate upon which the reflective surface is deposited and a spacer support frame, each of the hinge, mirror plate and spacer support frame are fabricated from a single piece of material.

37. The spatial light modulator of claim 36, further comprising means for removing the voltage from the electrode corresponding to the selected micro mirror permitting the micro mirror to return to an unbiased position.

38. A spatial light modulator, comprising:

means for deflecting having an upper surface;

means for rotating the deflecting means about an axis; and

means for reflecting light, the reflecting means deposited on the upper surface of the deflecting means and above the rotating means to substantially conceal the rotating means.