Method and device for multistate interferometric light modulation

• US 20060077508A1
• Filed: 04/22/2005
• Published: 04/13/2006
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: IDC, LLC
• Inventors: Gally, Brian J., Chui, Clarence, Cummings, William J.
• Granted Patent: US 7,372,613 B2
• Time in Patent Office: Days
• US Class Current: 359/245
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

A multi-state light modulator comprises a first reflector. A first electrode is positioned at a distance from the first reflector. A second reflector is positioned between the first reflector and the first electrode. The second reflector is movable between an undriven position, a first driven position, and a second driven position, each having a corresponding distance from the first reflector. In one embodiment, the three positions correspond to reflecting white light, being non-reflective, and reflecting a selected color of light. Another embodiment is a method of making the light modulator. Another embodiment is a display including the light modulator.

Claims

1. A light modulator, comprising:

a fixed reflector comprising an electrically conductive layer and a partially reflective layer;

an electrode positioned at a distance from the fixed reflector and defining a first cavity therebetween; and

a movable reflector comprising an electrically conductive material, the movable reflector positioned between the fixed reflector and the electrode, the movable reflector being movable between an undriven position, a first driven position, and a second driven position, wherein the first driven position is closer to the fixed reflector than is the undriven position and wherein the second driven position is farther from the fixed reflector than is the undriven position.

2. A light modulator, comprising:

a first reflector;

a first electrode positioned at a distance from the first reflector; and

a second reflector positioned between the first reflector and the first electrode, the second reflector being movable between an undriven position, a first driven position, and a second driven position, wherein the first driven position is closer to the first reflector than is the undriven position and wherein the second driven position is farther from the first reflector than is the undriven position.

3. The modulator of claim 2, wherein the first reflector is at least partially transparent.

4. The modulator of claim 2, wherein the first reflector comprises at least one layer of reflective material.

5. The modulator of claim 2, wherein the first reflector comprises a second electrode, and wherein the second reflector comprises a third electrode.

6. The modulator of claim 5, wherein each of the second electrode and the third electrode comprises a layer of conductive material.

7. The modulator of claim 5, wherein the second reflector moves to the first driven position in response to a voltage potential applied between the second electrode and the third electrode.

8. The modulator of claim 7, wherein the modulator reflects white light when the second reflector is in the first driven position.

9. The modulator of claim 5, wherein the second reflector moves to the second driven position in response to a voltage potential applied between the first electrode and the third electrode.

10. The modulator of claim 9, wherein the modulator selectively reflects light in a range of visible wavelengths associated with a color when the second reflector is in the second driven position.

11. The modulator of claim 2, wherein the modulator substantially absorbs incident visible light when the second reflector is in the undriven position.

12. A method of driving a MEMS device comprising a first electrode, a second electrode, and a movable electrode positioned between the first electrode and the second electrode and configured to move to at least two positions therebetween, the method comprising:

applying a first voltage potential difference between the first electrode and the movable electrode so as to drive the movable electrode to a position substantially in contact with a dielectric layer, wherein an attractive force is created between the movable electrode and the dielectric layer; and

applying a second voltage potential difference between the first electrode and the movable electrode and a third voltage potential difference between the second electrode and the movable electrode so as to overcome the attractive force between the movable electrode and the dielectric layer and to drive the movable electrode away from the dielectric layer.

13. The method claim 12, wherein the attractive force comprises a stictional force.

14. A method of fabricating a multistate light modulator, comprising:

forming a first reflector;

forming a first electrode positioned at a distance from the first reflector; and

forming a second reflector positioned between the first reflector and the first electrode, the second reflector movable between an undriven position, a first driven position, and a second driven position, wherein the first driven position is closer to the first reflector than is the undriven position and wherein the second driven position is farther from the first reflector than is the undriven position.

15. The method of claim 14, wherein forming the first reflector comprises forming a second electrode and wherein forming the second reflector comprises forming a third electrode.

16. The modulator of claim 15, wherein forming each of the second electrode and the third electrode comprises forming a layer of conductive material.

17. A light modulator formed by the method of claim 14.

18. A display comprising a plurality of display elements, each of the display elements comprising:

a first reflective member;

a first conductive member positioned at a distance from the first reflective member; and

a second reflective member positioned between the first reflective member and the first conductive member, the second reflective member being movable between an undriven position, a first driven position, and a second driven position, wherein the first driven position is closer to the first reflective member than is the undriven position and wherein the second driven position is farther from the first reflective member than is the undriven position.

19. The display of claim 18, wherein the first reflective member is at least partially transparent.

20. The display of claim 18, further comprising a substantially transparent substrate which transmits incident light to the second reflective member.

21. The display of claim 18, wherein the first reflective member comprises at least one layer of reflective material.

22. The display of claim 18, wherein the second reflective member comprises at least one layer of reflective material.

23. The display of claim 18, wherein the first reflective member comprises a second conductive member and the second reflective member comprises a third conductive member.

24. The display of claim 23, wherein each of the second conductive member and the third conductive member comprises a layer of conductive material.

25. The display of claim 23, wherein the second reflective member moves to the first driven position in response to a voltage potential applied between the second conductive member and the third conductive member.

26. The display of claim 25, wherein each display element reflects white light when the second reflective member of the display element is in the first driven position.

27. The display of claim 23, wherein the second reflective member moves to the second driven position in response to a voltage potential applied between the first conductive member and the third conductive member.

28. The display of claim 27, wherein each display element selectively reflects light in a range of visible wavelengths associated with a respective color when the second reflective member of the display element is in the second driven position.

29. The display of claim 18, wherein each display element substantially absorbs incident visible light when the second reflective member of the display element is in the undriven position.