Device and method for manipulation of thermal response in a modulator

• US 20060077152A1
• Filed: 06/10/2005
• Published: 04/13/2006
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Chui, Clarence, Mignard, Marc
• Granted Patent: US 7,554,714 B2
• Time in Patent Office: Days
• US Class Current: 345/85
• CPC Class Codes: G01J 3/26 using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
• 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: G02B 26/0866 the reflecting means being moved or deformed by thermal means

Abstract

By varying the spacing between two surfaces, one of which is disposed in front of the other, an interferometric modulator selectively creates constructive and/or destructive interference between light waves reflecting off the two surfaces. The desired spacing can be achieved by deforming one or both surfaces. A heating element associated with a particular surface causes the deformation by heating the material that forms one or both of the surfaces. By varying the amount of applied heat, the amount of deformation is varied, thus allowing the distance between the surfaces to be controlled and thereby creating constructive and/or destructive interference as desired.

Claims

1. An interferometric light modulating device, comprising:

a partially-reflective part;

a thermally-responsive movable part which moves relative to the partially-reflective part in response to changes of temperature; and

a heat source configured to heat the movable part to vary a distance between the partially-reflective part and the movable part.

2. The interferometric light modulating device of claim 1, wherein the heat source is in contact with the movable part.

3. The interferometric light modulating device of claim 2, wherein the heat source is a resistive heater.

4. The interferometric light modulating device of claim 3, wherein the resistive heater comprises a metal wire.

5. The interferometric light modulating device of claim 4, wherein the heat source comprises a dielectric material disposed between and electrically insulating the metal wire from the movable part.

6. The interferometric light modulating device of claim 5, wherein the dielectric material is an oxide.

7. The interferometric light modulating device of claim 5, wherein the metal is chosen from the group consisting of nickel, chromium, nickel alloys, chromium alloys and nickel-chromium alloys.

8. The interferometric light modulating device of claim 1, wherein the movable part comprises a thermally responsive material chosen from the group consisting of nickel, aluminum, nickel alloys, aluminum alloys, nickel-aluminum alloys, gold, platinum, rhodium, copper and silver.

9. The interferometric light modulating device of claim 8, wherein the movable part comprises a layer of the thermally responsive material.

10. The interferometric light modulating device of claim 1, wherein the movable part comprises at least two layers of material, wherein the layers of material have different thermal expansion coefficients.

11. The interferometric light modulating device of claim 10, wherein the movable part comprises a bimetallic sandwich.

12. The interferometric light modulating device of claim 11, wherein the bimetallic sandwich comprises a layer comprising nickel or copper and an other layer comprising iron or titanium.

13. The interferometric light modulating device of claim 1, wherein the movable part is a mirror attached to and spaced from a support comprising a thermally responsive material.

14. The interferometric light modulating device of claim 1, wherein the partially-reflective part has a fixed position.

15. The interferometric light modulating device of claim 1, further comprising:

a display;

a processor that is in electrical communication with the display, the processor being configured to process image data;

a memory device in electrical communication with the processor.

16. The display system of claim 15, further comprising:

a first controller configured to send at least one signal to the display; and

a second controller configured to send at least a portion of the image data to the first controller.

17. The display system of claim 15, further comprising:

an image source module configured to send the image data to the processor.

18. The display system of claim 17, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

19. The display system of claim 15, further comprising:

an input device configured to receive input data and to communicate the input data to the processor.

20. A display device comprising a plurality of micromechanical display elements, each display element comprising:

a transmissive layer;

a reflective layer parallel to and supported spaced from the transmissive layer by a thermally responsive material; and

a heating element in thermal communication with the thermally responsive material.

21. The display device of claim 20, wherein the heating element is a resistive heater.

22. The display device of claim 21, wherein each display element further comprises a switch electrically coupled to the heater, wherein the switch adjusts a current flowing through the heater, thereby regulating a temperature of the heater.

23. The display device of claim 22, wherein the switch is a transistor.

24. The display device of claim 22, wherein each switch is independently controllable.

25. The display device of claim 21, wherein the display elements are organized in groups, wherein a switch electrically coupled to the heaters for the groups is configured to adjust a current flowing through the heaters, thereby regulating a temperature of the heaters.

26. The display device of claim 25, wherein the groups comprise rows or columns of display elements.

27. The display device of claim 20, further comprising a heat source for providing heat energy to the heating element, wherein the heating element comprises a heat absorbing material.

28. A method for modulating electromagnetic radiation, comprising:

providing a micromechanical device, comprising;

a thermally responsive part which moves in response to changes of temperature;

a temperature modulator;

a first partially reflective surface; and

a second surface spaced from and generally parallel to the first surface, wherein movement of the thermally responsive part changes a distance between the first and second surfaces;

adjusting the temperature modulator to change a temperature of the thermally responsive part, thereby varying the distance between the first and second surfaces.

29. The method of claim 28, wherein varying the distance alters an interference behavior of electromagnetic waves impinging on the first and second surfaces.

30. The method of claim 29, wherein the electromagnetic waves are visible light waves.

31. The method of claim 30, wherein varying the distance produces constructive interference centered at a desired light frequency.

32. The method of claim 30, wherein varying the distance comprises positioning the first surface at a plurality of distances from the second surface to produce constructive interference centered at a plurality of desired light frequencies.

33. The method of claim 28, wherein changing the temperature comprises transmitting heat from the temperature modulator to the thermally responsive part.

34. The method of claim 33, wherein transmitting heat comprises conductively heating the thermally responsive part, wherein the temperature modulator is a resistive heater.

35. The method of claim 34, wherein adjusting the temperature modulator comprises varying a level of current flowing to the resistive heater among three or more levels.

36. A method for producing a micromechanical device, comprising:

forming a first reflective layer;

forming a second reflective layer spaced from the first reflective layer; and

forming a heating element in thermal communication with the second reflective layer.

37. The method of claim 36, wherein the second reflective layer comprises a heat expansive metal.

38. The method of claim 37, further comprising forming an electrical insulator between the heating element and the heat expansive metal.

39. The method of claim 36, wherein forming the heating element comprises forming a metal wire.

40. The method of claim 36, wherein at least one of the first reflective layer and the second reflective layer is partially transparent.

41. An interferometric modulator formed by the method of claim 36.

42. An interferometric modulator, comprising:

a transmissive layer;

a reflective layer; and

a means for actuating movement of the reflective layer using thermal energy.