Method and device for compensating for color shift as a function of angle of view

• US 20060077522A1
• Filed: 01/21/2005
• 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: Kothari, Manish
• Granted Patent: US 7,630,123 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• 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 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 5/0236 the diffusion taking place within the volume of the element
• CPC Class Codes: G02B 5/0278 used in transmission

Abstract

In one embodiment of the invention, a display is provided and includes a plurality of interferometric display elements. The display further includes at least one diffuser. Optical properties of the diffuser are selected to reduce color shift of the display when viewed from at least one angle.

Claims

1. A display comprising:

at least one interferometric modulator configured to reflect incident light, the at least one interferometric modulator having an optical response that depends at least in part on angle of view and wavelength of the incident light; and

a diffuser positioned in an optical path to the at least one interferometric modulator, the diffuser having an optical response that is substantially matched to the optical response of the interferometric modulator to maintain substantially the same composition of color at different angles of view.

2. The display of claim 1, wherein the optical response of the diffuser depends at least in part on angle of view.

3. The display of claim 1, wherein the diffuser comprises a non-lambertian diffuser.

4. The display of claim 1, wherein the optical response of the diffuser falls off with angle of view.

5. The display of claim 1, wherein the diffuser comprises a high gain diffuser.

6. The display of claim 5, wherein the high gain diffuser has a full width at half maximum of between about 10°

and 30°

.

7. The display of claim 1, wherein the diffuser comprises a low gain diffuser.

8. The display of claim 7, wherein the low gain diffuser haves a full width at half maximum of between about 60°

and 100°

.

9. The display of claim 1, wherein the diffuser and interferometric modulator are configured to produce a combined optical response that reduces angular color shift to less than about 10 to 20 nanometers for an angle-of-view change of about 50 degrees.

10. A display comprising:

at least one interferometric modulator having a spectral responsivity that varies with angle of view, θ

, such that color varies with angle of view; and

a non-lambertian diffuser positioned in an optical path to the at least one interferometric modulator, the non-lambertian diffuser having an optical response that varies with angle of view, said diffuser substantially reducing variation of color with angle of view.

11. The display of claim 10, wherein the spectral responsivity of the interferometric modulator for a normal angle of view of 0°

includes a spectral line that is centered about a non-visible wavelength and that extends into visible wavelengths.

12. The display of claim 11, wherein the'"'"'spectral line is centered in the infrared.

13. The display of claim 11, wherein the spectral line is centered at a wavelength between about 700 to about 1000 nanometers.

14. The display of claim 11, wherein said interferometric modulator together with said diffuser have a spectral responsivity for said normal angle of view having a spectral line centered in the visible wavelength range.

15. The display of claim 10, wherein the diffuser comprises a high gain diffuser.

16. The display of claim 10, wherein the diffuser comprises a low gain diffuser.

17. The display of claim 10, wherein the optical response of the diffuser has a peak value at a non-zero angle of view for a normal angle of incidence.

18. The display of claim 17, wherein the optical response of the diffuser has a peak value at an angle of view greater than about 5 degrees for light incident on the diffuser at an angle of incidence, θ

_i, of about 0°

.

19. The display of claim 10, wherein the optical response of the diffuser is dependent on angle of incidence of light on the diffuser.

20. The display of claim 19, wherein the optical response of the diffuser is peaked at an angle of view that is unequal to the angle of incidence of the light on the diffuser.

21. The display of claim 20, wherein said peaked angle of view is different for different angles of incidence.

22. The display of claim 10, wherein the optical response of the diffuser further depends on the wavelength of light.

23. A method of fabricating a display comprising:

selecting a diffuser having an optical response; and

disposing the diffuser in front of an interferometric modulator array, the interferometric modulator array having an optical response that depends on angle of view,

wherein selecting the diffuser comprises substantially matching the optical response of the diffuser and the optical response of the interferometric modulator array to reduce angular color shift with angle-of-view of the display.

24. The method of claim 23, wherein substantially matching the optical response of the diffuser and the optical response of the interferometric modulator array comprises determining the optical response of the diffuser that with the optical response of the interferometric modulator produces a combined optical response that reduces angular color shift with angle-of-view of the display to less than a predetermined tolerance.

25. The method of claim 24, wherein the predetermined tolerance comprises a difference between a wavelength of a peak intensity of the combined optical response produced at any two angles of view within a predetermined range of angles of view.

26. The method of claim 23, wherein the optical response of the at least one interferometric modulator has an intensity that depends at least in part on the angle of view and the wavelength of the incident light.

27. The method of claim 23, wherein the optical response of the diffuser has an intensity that depends at least in part on angle of incidence of light and on angle of view.

28. The method of claim 27, wherein the optical response of the diffuser further depends at least in part on the wavelength of light.

29. A display fabricated by the method of claim 23.

30. A method of tailoring optical properties of a display comprising an interferometric modulator having a spectral responsivity and a diffuser having an optical response, the method comprising:

selecting at least one property of the diffuser with reference to the spectral responsivity of the interferometric modulator so as to reduce color shift of the display.

31. The method of claim 30, wherein selecting at least one property of the diffuser comprises determining the optical response of the diffuser based on the spectral responsivity of the interferometric modulator and a desired spectral responsivity of the display.

32. The method of claim 31, wherein determining the optical response of the diffuser comprises calculating D(θ

_i, θ

) by solving the equation,

$R^{\mathrm{\prime <br><br>}}<br><br>\left(\mathrm{\theta <br><br>},\mathrm{\lambda <br><br>}\right)=\underset{{\mathrm{\theta <br><br>}}_i}{\sum <br><br>}<br><br>D<br><br>\left({\mathrm{\theta <br><br>}}_i,\mathrm{\theta <br><br>}\right)<br><br>R<br><br>\left({\mathrm{\theta <br><br>}}_i,\mathrm{\lambda <br><br>}\right).$

33. The method of claim 30, wherein selecting at least one property of the diffuser comprises selecting variation in diffuser response with angle of view to be peaked at an angle other than the angle of incidence of light incident on the diffuser.

34. The method of claim 30, wherein selecting at least one property of the diffuser comprises selecting variation in response with angle of view to be peaked at an angle other than θ

=0°

.

35. The method of claim 30, further comprising selecting at least one property of the interferometric modulator affecting the spectral responsivity.

36. The method of claim 35, wherein selecting the at least one property of the diffuser comprises selecting the at least one property of the diffuser with reference to the spectral responsivity of the interferometric modulator so as to reduce the color shift of the display to less than a predetermined target value.

37. The method of claim 30, wherein selecting at least one property of the diffuser comprises selecting material properties of the diffuser.

38. The method of claim 30, wherein the color shift is a difference in wavelength between spectral lines in a spectral responsivity for the display when from viewed any two of a range of angles.

39. The method of claim 38, wherein the range of angles is between about −

40 degrees and 40 degrees with respect to an optical axis through the display and the color shift is reduced to between about 5 and 30 nm for said range of angles.

40. A display system for producing an image, the system comprising:

at least one interferometric modulator having a spectral responsivity that depends at least in part on angle of view of the display; and

a diffuser positioned in at least one optical path through the at least one interferometric modulator,

wherein the interferometric modulator is configured to at least partially encrypt the image from view and wherein the diffuser is configured to decrypt the image.

41. The system of claim 40, wherein the diffuser has an optical response that depends at least in part on the wavelength of light.

42. A method of limiting view of a display to authorized viewers, the method comprising:

selecting at least one interferometric modulator having a spectral responsivity that depends at least in part on angle of view of the display;

reflecting light indicative of an image from the at least one interferometric modulator, the interferometric modulator being configured to at least partially obscure the image from view; and

diffusing the reflected light from the at least one interferometric modulator with a diffuser having an optical response, wherein the optical response of the diffuser is configured to so as to decrypt the image.

43. The system of claim 42, wherein a spectral responsivity for the display is produced that is shifted more toward the visible wavelengths than the spectral responsivity of the interferometric modulators.