INTERFEROMETRIC MODULATOR DISPLAYS WITH REDUCED COLOR SENSITIVITY

• US 20080288225A1
• Filed: 05/18/2007
• Published: 11/20/2008
• Est. Priority Date: 05/18/2007
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Djordjev, Kostadin
• Granted Patent: US 8,111,262 B2
• Time in Patent Office: Days
• US Class Current: 703/6
• 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 27/0012 Optical design, e.g. procedures, algorithms, optimisation routines

Abstract

Methods are described for selecting reflective layer distances in an interferometric modulator display that result in reduced color sensitivity to temperature and process variation. Colors are selected for interferometric modulator subpixels that correspond to a minimum in the rate that the colors change with respect to reflective layer distance. In some cases, colors are selected that deviate from the minimums in order to obtain a desired target color (e.g., a desired white point).

Claims

1. A method of selecting a distance between two reflective surfaces for each one of multiple interferometric modulators for use in a display, the method comprising:

determining first distances between the two reflective surfaces in each one of the multiple interferometric modulators where the rate of change of color reflected from the multiple interferometric modulators as a function of distance is a local minimum;

determining the color of light that would be reflected from the display when substantially all interferometric modulators in the display are in a bright state; and

if the color is not substantially close to a desired target color, determining second distances between the two reflective surfaces for each one of the multiple interferometric modulators by varying the first distances until the color of light that would be reflected from the display when substantially all interferometric modulators in the display are in a bright state is substantially close to the desired target color.

2. The method of claim 1, comprising determining different distances between two reflective surfaces for at least two interferometric modulators in the display.

3. The method of claim 2, wherein three different distances are determined.

4. A method of selecting colors for an interferometric modulator display, the method comprising:

determining a color for at least one interferometric modulator for which the rate of change of the color with respect to distance between reflective surfaces in the interferometric modulator is a local minimum; and

varying the color so that a certain color reflected from the display is substantially close to a desired target color.

5. The method of claim 4, wherein determining the color comprises determining u′

and v′

color parameters for the interferometric modulator.

6. The method of claim 4, wherein three or more different colors are determined for three or more different interferometric modulators.

7. The method of claim 6, wherein the certain color reflected from the display is generated by reflection from all three or more interferometric modulators.

8. The method of claim 7, wherein the colors for all three or more interferometric modulators are varied so that the certain color reflected from the display is substantially close to the desired target color.

9. The method of claim 6, wherein the three or more different colors include substantially red, substantially green, and substantially blue.

10. The method of claim 6, wherein the three or more different colors include substantially yellow.

11. The method of claim 4, wherein the desired target color is substantially white.

12. The method of claim 11, wherein the desired target color is D65 standard white.

13. The method of claim 4, wherein determining the rate of change of color with respect to distance comprises determining the color difference in u′

-v′

color space between colors generated for two different reflective surface distances.

14. The method of claim 13, wherein determining the color difference in u′

-v′

color space comprises determining the value √

{square root over ((u′

₂-u′

₁)²+(v′

₂-v′

₁)²)}{square root over ((u′

₂-u′

₁)²+(v′

₂-v′

₁)²)}, wherein u′

₁ and v′

₁ are color parameters corresponding to the first reflective surface distance and u′

₂ and v′

₂ are color parameters corresponding to the second reflective surface distance.

15. The method of claim 13, wherein the two different reflective surface distances are about 1 nm apart.

16. The method of claim 4, wherein determining the color comprises modeling the optical response from the interferometric modulator.

17. The method of claim 16, wherein the optical model includes one or more thickness of a material layer in the interferometric modulator, one or more refractive index of a material layer in the interferometric modulator, and one or more extinction coefficient of a material layer in the interferometric modulator.

18. The method of claim 4, wherein the color is varied less than 0.03 units in u′

-v′

color space from the color corresponding to the local minimum.

19. A computer-readable medium comprising computer-executable instructions for performing the method comprising:

determining a color for at least one interferometric modulator for which the rate of change of the color with respect to distance between reflective surfaces in the interferometric modulator is a local minimum; and

varying the color so that a certain color reflected from the display is substantially close to a desired target color.

20. The computer-readable medium of claim 19, wherein the medium comprises a computer hard disk.

21. The computer-readable medium of claim 19, wherein the medium comprises an optically read disk.

22. The computer-readable medium of claim 19, comprising computer-executable instructions for determining u′

and v′

color parameters for the interferometric modulator.

23. The computer-readable medium of claim 19, comprising computer-executable instructions for determining three or more different colors for three or more different interferometric modulators.

24. The computer-readable medium of claim 23, comprising computer-executable instructions for varying the colors for all three or more interferometric modulators so that the certain color reflected from the display is substantially close to the desired target color.

25. The computer-readable medium of claim 19, comprising computer-executable instructions for determining the color difference in u′

-v′

color space between colors generated for two different reflective surface distances.

26. A method of manufacturing an interferometric modulator display, comprising:

selecting distances between reflective surfaces in each interferometric modulator by;

determining first distances between two reflective surfaces in each interferometric modulator where the rate of change of color reflected from each interferometric modulator as a function of distance is a local minimum;

determining the color of light that would be reflected from the display when substantially all interferometric modulators in the display are in a bright state; and

if the color is not substantially close to a desired target color, determining second distances between the two reflective surfaces for each interferometric modulator by varying the first distances until the color of light that would be reflected from the display when substantially all interferometric modulators in the display are in a bright state is substantially close to the desired target color; and

manufacturing an array of interferometric modulators having the selected distances.

27. An interferometric modulator display, comprising at least one interferometric modulator having a bright state color within 0.04 units in u′

-v′

color space of a color at which the rate of change of color with respect to distance between reflective surfaces in the interferometric modulator is a local minimum.

28. The display of claim 27, wherein the interferometric modulator has a bright state color within 0.03 units in u′

-v′

color space of the color at which the rate of change of color with respect to distance between reflective surfaces in the interferometric modulator is a local minimum.

29. The display of claim 27, wherein the interferometric modulator has a bright state color within 0.02 units in u′

-v′

color space of the color at which the rate of change of color with respect to distance between reflective surfaces in the interferometric modulator is a local minimum.

30. The display of claim 27, wherein a plurality of interferometric modulators in the display have a bright state color within 0.04 units in u′

-v′

color space of a color at which the rate of change of color with respect to distance between reflective surfaces in the interferometric modulators is a local minimum.

31. The display of claim 27, comprising:

a first set of interferometric modulators having a bright state color within 0.04 units in u′

-v′

color space of a first color at which the rate of change of color with respect to distance between reflective surfaces in the first set of interferometric modulators is a local minimum;

a second set of interferometric modulators having a bright state color within 0.04 units in u′

-v′

color space of a second color at which the rate of change of color with respect to distance between reflective surfaces in the second set of interferometric modulators is a local minimum; and

a third set of interferometric modulators having a bright state color within 0.04 units in u′

-v′

color space of a third color at which the rate of change of color with respect to distance between reflective surfaces in the third set of interferometric modulators is a local minimum.

32. The display of claim 31, wherein the first color is substantially red, the second color is substantially green, and the third color is substantially blue.

33. The display of claim 27, further comprising:

a processor that is in electrical communication with the interferometric modulator, said processor being configured to process image data; and

a memory device in electrical communication with said processor.

34. The display of claim 33, further comprising:

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

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

35. The display of claim 33, further comprising an image source module configured to send said image data to said processor.

36. The display of claim 35, wherein said image source module comprises at least one of a receiver, transceiver, and transmitter.

37. The display of claim 33, further comprising an input device configured to receive input data and to communicate said input data to said processor.

38. A display, comprising:

first means for reflecting light; and

second means for reflecting light, wherein the distance between the first and second means is such that light interferometrically reflected from the first and second means has a color within 0.04 units in u′

-v′

color space of a color at which the rate of change of color with respect to distance between the first and second means is a local minimum.

39. The display of claim 38, wherein the first means comprises a partially reflective surface.

40. The display of claim 38 or 39, wherein the second means comprises a reflective surface.

41. The display of claim 40, wherein the reflective surface is movable.

42. An interferometric modulator display, comprising at least one interferometric modulator having a bright state color that varies less than about 0.03 units in u′

-v′

color space over a 20°

C. temperature change.

43. The display of claim 42, wherein the bright state color varies less than about 0.02 units in u′

-v′

color space over a 20°

C. temperature change.

44. The display of claim 42, wherein the bright state color varies less than about 0.01 units in u′

-v′

color space over a 20°

C. temperature change.

45. The display of claim 42, wherein a plurality of interferometric modulators in the display have a bright state color that varies less than about 0.02 units in u′

-v′

color space over a 20°

C. temperature change.