Systems and methods for measuring color and contrast in specular reflective devices

• US 7,417,735 B2
• Filed: 08/05/2005
• Issued: 08/26/2008
• Est. Priority Date: 09/27/2004
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: IDC, LLC
• Inventors: Cummings, William, Gally, Brian
• Primary Examiner(s): Toatley, Jr.; Gregory J.
• Assistant Examiner(s): GIGLIO, BRYAN J
• Application Number:
  US11/198,603
• Publication Number:
  US 20060066856A1
• Time in Patent Office: 1,117 Days
• Field of Search: 356/328, 356/402, 356/408, 356/305, 356/243.5, 359/290, 359/291, 359/295, 348/755
• US Class Current: 356/408
• 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: H04N 17/02 for colour television signals
• CPC Class Codes: H04N 9/3194 including sensor feedback

Abstract

Disclosed herein are systems and methods for measuring color and contrast in specular reflective devices such as interferometric modulators. To make color and contrast determinations, light reflected from a specular reflective device may be measured in-line with illumination of the device. The measurements may include measuring the spectra of light reflected from the device being tested as well as from specular bright and dark standards. The spectra may be used to determine a reflectance spectrum and color parameters for the specular reflective device.

Claims

1. A method of measuring color or contrast of one or more sample interferometric modulators, comprising:

measuring a spectrum of light reflected from a bright standard located on a substrate;

measuring a spectrum of light reflected from the one or more sample interferometric modulators also located on the substrate; and

determining a reflectance spectrum of the sample interferometric modulators based on the spectra of light reflected from the bright standard and one or more sample interferometric modulators.

4. The method of claim 1, wherein the light reflected from the bright standard and sample interferometric modulators includes light from an illumination source that is specularly reflected from the bright standard and sample interferometric modulators.

5. The method of claim 4, wherein light reflected from the bright standard and sample interferometric modulators includes light reflected substantially perpendicular to reflective surfaces of the standards and sample interferometric modulators.

6. The method of claim 1, wherein the spectrum of light reflected from the one or more sample interferometric modulators is measured for both the sample interferometric modulators in a bright state and the sample interferometric modulators in a dark state.

7. The method of claim 1, wherein the spectrum of light reflected from the one or more sample interferometric modulators is measured for the sample interferometric modulators in an undriven state, an overdriven state, a memory dark state, and a memory bright state.

8. The method of claim 1, wherein the sample interferometric modulators includes a first set of interferometric modulators adapted to reflect light of a first color and a second set of interferometric modulators adapted to reflect light of a second color, wherein the first color is different from the second color, wherein the spectrum of light reflected from the one or more sample interferometric modulators is measured separately for the first set of interferometric modulators and the second set of interferometric modulators.

9. The method of claim 1, wherein the bright standard includes a specular reflective standard.

12. The method of claim 1, further comprising determining color parameters from the reflectance spectrum.

13. The method of claim 12, further comprising determining contrast of the sample interferometric modulators by comparing a color parameter determined for the sample interferometric modulators in a bright state with a color parameter determined for the sample interferometric modulators in a dark state.

2. A method of measuring color or contrast of one or more sample interferometric modulators, comprising:

measuring a spectrum of light reflected from a bright standard;

measuring a spectrum of light reflected from the one or more sample interferometric modulators;

measuring a spectrum of light reflected from a dark standard; and

determining a reflectance spectrum of the sample interferometric modulators based on the spectra of light reflected from the bright standard and one or more sample interferometric modulators.

3. The method of claim 2, wherein the dark standard includes at least one etalon.

10. The method of claim 2, wherein determining a reflectance spectrum of the sample interferometric modulators includes determining relative spectral reflectivity of the sample interferometric modulators compared to spectral reflectivity of the bright and dark standards.

11. The method of claim 10, wherein determining a reflectance spectrum of the sample interferometric modulators includes multiplying the relative spectral reflectivity by the spectral reflectivity of the bright standard.

14. An integrated reflective display element and test standard wafer, comprising:

a plurality of reflective display elements adapted for use in a display, wherein the reflective display elements are interferometric modulators; and

a bright standard, wherein the reflective display elements and the bright standard are present on a single wafer.

15. The wafer of claim 14, further comprising a dark standard, wherein the reflective display elements, the bright standard, and the dark standard are present on a single wafer.

16. The wafer of claim 14, wherein the bright standard comprises a reflective material deposited on a transparent substrate.

17. The wafer of claim 15, wherein the dark standard comprises at least one etalon.

18. A wafer, comprising:

a plurality of first means for reflecting light for use in a display, wherein the first means comprises interferometric modulators; and

second means for reflecting light at an intensity greater than light reflected from the first means, wherein the first means and the second means are present on a single wafer.

19. The wafer of claim 18, wherein the second means comprises a bright standard.

20. An in-line lighting and measurement system, comprising:

an illumination source adapted to illuminate a specularly reflective device;

a detector adapted to detect light reflected from the specularly reflective device;

a specularly reflective bright standard adapted to specularly reflect light from the illumination source into the detector, thereby providing a reflectance spectrum standard for use in determining a reflectance spectrum of the specularly reflective device; and

a specularly reflective dark standard comprising an etalon adapted to specularly reflect light from the illumination source into the detector, thereby providing a second reflectance spectrum standard for use in determining the reflectance spectrum of the specularly reflective device.

21. The system of claim 20, further comprising a shutter adapted to block light from the illumination source from reaching the detector.

22. The system of claim 20, wherein the detector comprises a spectrometer.

23. A method of determining whether an array of interferometric modulators are suitable for use in a display, comprising:

determining color parameters for at least some of the interferometric modulators in an un-driven state, a memory dark state, a memory bright state, and an over-driven state; and

identifying the array as suitable for use as a display based on said determining.

24. The method of claim 23, wherein the array includes a first set of interferometric modulators adapted to reflect light of a first color and a second set of interferometric modulators adapted to reflect light of a second color, wherein the first color is different from the second color, wherein color parameters are determined for both the first set of interferometric modulators and the second set of interferometric modulators.

25. The method of claim 24, wherein said identifying is based on a color gamut indicated by the color parameters.

26. The method of claim 23, wherein said identifying is based on a contrast ratio determined as a ratio of one of the color parameters measured in two different states.

27. An integrated interferometric modulator and test standard wafer manufactured by a process that comprises:

a plurality of material deposition steps;

a plurality of patterning steps that define regions for material removal; and

a plurality of material removal steps, wherein the patterning steps are used to define a plurality of interferometric modulators and separately at least one reflectivity standard selected from the group consisting of a bright standard and a dark standard.

28. The wafer of claim 27, wherein the at least one reflectivity standard includes a region of the wafer where all but one or more high reflectivity materials have been removed.

29. The wafer of claim 27, wherein the at least one reflectivity standard includes a region of the wafer where a static etalon is formed.

30. A method of manufacturing an interferometric modulator array, comprising:

forming a plurality of interferometric modulators on a substantially transparent substrate;

forming a reflectivity standard on the substrate, wherein the reflectivity standard is selected from the group consisting of a bright standard and a dark standard.

31. The method of claim 30, wherein the reflectivity standard and interferometric modulators are both formed by an identical series of material deposition and removal steps, wherein the interferometric modulators and reflectivity standard are exposed to different patterning.

32. A method of measuring color of an interferometric modulator on a substrate, comprising:

detecting light reflected from the interferometric modulator, determining a first reference reflectivity using a means for reflecting a maximum amount of light also on the substrate; and

determining the color of the interferometric modulator from the detected light and first reference reflectivity.

34. The method of claim 32, wherein the step of determining the color includes determining a reflectance spectrum of the interferometric modulator.

35. The method of claim 32, wherein the step of determining the color includes determining one or more color parameters of the interferometric modulator.

33. A method of measuring color of an interferometric modulator, comprising:

detecting light reflected from the interferometric modulator;

determining a first reference reflectivity using a means for reflecting a maximum amount of light;

determining a second reference reflectivity using a means for reflecting a minimum amount of light;

determining the color of the interferometric modulator from the detected light and the first and second reference reflectivities.

36. An interferometric modulator display comprising a plurality of interferometric modulators identified as suitable for use in the display by:

detecting light reflected from at least some of the interferometric modulators, wherein the interferometric modulators are located on a substrate;

detecting light reflected from a bright standard also located on the substrate; and

determining a reflectance spectrum, one or more color parameters, and/or a contrast ratio of the interferometric modulators.

39. The display of claim 36, further comprising:

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

a memory device in electrical communication with said processor.

40. The display as recited in claim 39, further comprising:

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

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

41. The display as recited in claim 39, further comprising an image source module configured to send said image data to said processor.

42. The display as recited in claim 41, wherein said image source module comprises at least one of a receiver, transceiver, and transmitter.

43. The display as recited in claim 39, further comprising an input device configured to receive input data and to communicate said input data to said processor.

37. An interferometric modulator display comprising a plurality of interferometric modulators identified as suitable for use in the display by:

detecting light reflected from at least some of the interferometric modulators;

detecting light reflected from a dark standard; and

determining a reflectance spectrum, one or more color parameters, and/or a contrast ratio of the interferometric modulators.

38. The display of claim 37, wherein the dark standard includes at least one etalon.