Measurement of the dynamic characteristics of interferometric modulators

• US 7,453,579 B2
• Filed: 09/09/2005
• Issued: 11/18/2008
• Est. Priority Date: 09/27/2004
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: IDC, LLC
• Inventors: Gally, Brian J., Cummings, William J., Kothari, Manish, Tang, Yongkang
• Primary Examiner(s): Chowdhury; Tarifur R
• Assistant Examiner(s): Cook; Jonathon D
• Application Number:
  US11/223,824
• Publication Number:
  US 20060077401A1
• Time in Patent Office: 1,166 Days
• Field of Search: 356/519
• US Class Current: 356/519
• 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: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

Various systems and methods of lighting a display are disclosed. In one embodiment, for example, a method includes applying a voltage waveform to the interferometric modulators, applying a voltage pulse to the interferometric modulators, detecting reflectivity of light from the interferometric modulators, and determining one or more quality parameters of the interferometric modulators based on the detecting reflectivity of light, where the applied voltage pulse causes the interferometric modulators to vary between an actuated and a non-actuated state, or an non-actuated state and an actuated state.

Claims

1. A method of testing a plurality of interferometric modulators, the method comprising:

applying a voltage waveform to the interferometric modulators to change the state of the interferometric modulators between an actuated and a released state, or a released state and an actuated state;

detecting light reflected from the interferometric modulators as a function of time while applying said voltage waveform; and

determining at least one response time parameters of the interferometric modulators based on said detecting, wherein the at least one parameter comprises one of the following;

a positive actuation response time (Tpa), a negative actuation response time (Tna), a positive release response time (Tpr), and a negative release response time (Tnr).

2. The method of claim 1, wherein said applying comprises applying the voltage waveform at a frequency of between 10 Hz and 5000 Hz.

3. The method of claim 2, wherein said applying comprises applying the voltage waveform at a frequency of between 50 Hz and 500 Hz.

4. The method of claim 3, wherein said applying comprises applying the voltage waveform at a frequency of between 50 Hz and 150 Hz.

5. The method of claim 4, wherein said applying comprises applying the voltage waveform at a frequency of about 100 Hz.

6. The method of claim 1, wherein the waveform is applied simultaneously to all interferometric modulators.

7. The method of claim 1, wherein said detecting comprises detecting the light reflected from less than all interferometric modulators.

8. The method of claim 1, wherein said detecting comprises measuring the reflected light with a photodetector.

9. The method of claim 1, wherein said detecting comprises measuring the reflected light through a diffuser positioned in front of the interferometric modulators.

10. The method of claim 1, wherein said detecting comprises measuring the reflected light at an angle that is substantially perpendicular to the interferometric modulators.

11. The method of claim 1, wherein the voltage waveform comprises a first portion at about an offset voltage level and a second portion at an actuation voltage level.

12. The method of claim 1, wherein the amplitude of the waveform is less than about 2 times the voltage necessary to cause an actuation of the interferometric modulators.

13. The method of claim 12, wherein the amplitude of the waveform is about 1.25 times the voltage necessary to cause an actuation of the interferometric modulators.

14. The method of claim 1, wherein the voltage waveform comprises a first portion at an actuation voltage level and a second portion at about an offset voltage level.

15. The method of claim 1, wherein the response time parameters are based on the slowest response time of one or more of the plurality of interferometric modulators.

16. The method of claim 1, wherein each of the plurality of interferometric modulators comprises a fixed reflective surface and a moveable reflective surface wherein the fixed reflective surface and the moveable reflective surface are configured to cause interference of light.

17. A system for testing a plurality of interferometric modulators, comprising:

an illumination source adapted to provide incident light to a plurality of interferometric modulators;

a voltage source configured to apply a voltage waveform to the interferometric modulators to vary the interferometric modulators between an actuated and a released state, or a released state and an actuated state;

an optical detector configured to detect light reflected from the plurality of interferometric modulators and produce a signal corresponding to the detected light; and

a computer configured to receive the signal from the optical detector and determine at least one response time parameters of the interferometric modulators based on the signal, wherein the at least one parameter comprises one of the following;

a positive actuation response time (Tpa), a negative actuation response time (Tna), a positive release response time (Tpr), and a negative release response time (Tnr).

18. The system of claim 17, wherein said voltage source is further configured to apply the voltage waveform at a frequency of between 10 Hz and 5000 Hz.

19. The system of claim 18, wherein said voltage source is further configured to apply the voltage waveform at a frequency of between 50 Hz and 500 Hz.

20. The system of claim 17, wherein said voltage source is further configured to apply the voltage waveform at a frequency of between 50 Hz and 150 Hz.

21. The system of claim 17, wherein the waveform is applied simultaneously to all interferometric modulators.

22. The system of claim 17, wherein said optical detector is further configured to detect the reflected light with a photodetector.

23. The system of claim 17, wherein said optical detector is further configured to detect the reflected light by measuring the reflected light through a diffuser positioned in front of the interferometric modulators.

24. The system of claim 17, wherein said optical detector is further configured to detect the reflected light by measuring the reflected light at an angle that is substantially perpendicular to the interferometric modulators.

25. The system of claim 17, wherein said computer receives a signal from said voltage source indicating when a voltage is applied to the interferometric modulators.

26. The system of claim 17, wherein the one or more response time parameters are based on the slowest response time of one or more of the plurality of interferometric modulators.

27. The system of claim 17, wherein each of the plurality of interferometric modulators comprises a fixed reflective surface and a movable reflective surface wherein the fixed reflective surface and the movable reflective surface are configured to cause interference of light.

28. A system for testing a plurality of interferometric modulators, comprising:

means for providing light to the plurality of interferometric modulators;

means for applying a voltage waveform to the interferometric modulators to vary the interferometric modulators between an actuated and a released state, or a released state and an actuated state;

means for detecting light reflected from the plurality of interferometric modulators;

means for producing a signal corresponding to the detected light; and

means for determining at least one response time parameters of the interferometric modulators based on the signal, wherein the at least one parameter comprises one of the following;

a positive actuation response time (Tpa), a negative actuation response time (Tna), a positive release response time (Tpr), and a negative release response time (Tnr).

29. The system of claim 28, wherein the light providing means comprises a broad-band light source.

30. The system of claim 28, wherein the voltage applying means comprises a voltage source.

31. The system of claim 28, wherein the detecting means comprises an optical detector.

32. The system of claim 28, wherein the detecting means comprises a spectrometer.

33. The system of claim 28, wherein the signal producing means comprises an optical detector.

34. The system of claim 28, wherein the determining means comprises a computer configured to receive the signal from the detecting means.

35. The system of claim 28, wherein the one or more response time parameters are based on the slowest response time of one or more of the plurality of interferometric modulators.

36. The system of claim 28, wherein each of the plurality of interferometric modulators comprises a fixed reflective surface and a movable reflective surface wherein the fixed reflective surface and the movable reflective surface are configured to cause interference of light.

37. A method of testing a plurality of interferometric modulators, the method comprising:

applying a voltage waveform to the interferometric modulators to vary the interferometric modulators between an actuated state and a released state, or a released state and an actuated state wherein the voltage applied to change the state of the interferometric modulators is applied while the interferometric modulators are subject to a bias voltage;

detecting light reflected from the interferometric modulators while applying the voltage waveform; and

determining at least one response time parameters of at least a portion of the interferometric modulators based on said detecting the reflected light, wherein the at least one parameter comprises one of the following;

a positive actuation response time (Tpa), a negative actuation response time (Tna), a positive release response time (Tpr), and a negative release response time (Tnr).

38. The method of claim 37, wherein the one or more response time parameters are based on the slowest actuation time of one or more interferometric modulators.

39. The method of claim 37, wherein said voltage waveform comprising a first portion a voltage level to place the interferometric modulators in an actuated state, a second portion at a bias voltage level and a third portion at a voltage level sufficient to release the interferometric modulators.

40. The method of claim 37, wherein said voltage waveform comprising a first portion a voltage level to place the interferometric modulators in a released state, a second portion at a bias voltage level and a third portion at a voltage level sufficient to actuate the interferometric modulators.

41. The method of claim 37, wherein each of the plurality of interferometric modulators comprises a fixed reflective surface and a movable reflective surface wherein the fixed reflective surface and the movable reflective surface are configured to cause interference of light.

42. A system of testing a plurality of interferometric modulators comprising:

a voltage source configured to apply a voltage waveform to the interferometric modulators to vary the interferometric modulators between an actuated and a released state, or a released state and an actuated state,

a light source positioned to illuminate the interferometric modulators;

a detector disposed to receive light from the interferometric modulators and produce a corresponding signal; and

a computer configured to receive the signal from the detector and determine, based on the signal, at least one response time parameters of at least a portion of the interferometric modulators during application of an actuation voltage or a release voltage, wherein the at least one parameter comprises one of the following;

a positive actuation response time (Tpa), a negative actuation response time (Tna), a positive release response time (Tpr), a negative release response time (Tnr).

43. The system of claim 42, wherein the one or more response parameters are based on the slowest actuation time of one or more interferometric modulators.

44. The system of claim 42, wherein each of the plurality of interferometric modulators comprises a fixed reflective surface and a movable reflective surface wherein the fixed reflective surface and the movable reflective surface are configured to cause interference of light.

45. A system for testing a plurality of interferometric modulators comprising:

means for applying a voltage waveform to the interferometric modulators to vary the interferometric modulators between an actuated and a released state, or a released state and an actuated state;

means for illuminating the interferometric modulators;

means for sensing light reflected from the interferometric modulators and producing a corresponding signal; and

means for determining, based on the signal, at least one response time parameters of the interferometric modulators during application of an actuation voltage or a release voltage, wherein the at least one parameter comprises one of the following;

a positive actuation response time (Tpa), a negative actuation response time (Tna), a positive release response time (Tpr), and a negative release response time (Tnr).

46. The system of claim 45, wherein the one or more response time parameters are based on the slowest actuation time of one or more interferometric modulators.

47. The system of claim 45, wherein said applying means comprises a controllable voltage source.

48. The system of claim 45, wherein said illuminating means comprises a light source.

49. The system of claim 45, wherein said sensing means comprises a photo detector.

50. The system of claim 45, wherein said determining means comprises a computer.

51. The system of claim 45, wherein each of the plurality of interferometric modulators comprises a fixed reflective surface and a movable reflective surface wherein the fixed reflective surface and the movable reflective surface are configured to cause interference of light.

52. A method of manufacturing a system for testing a plurality of interferometric modulators comprising:

providing a voltage source configured to apply a voltage waveform to the interferometric modulators to vary the interferometric modulators between an actuated and a released state, or released state and an actuated state;

positioning a light source to illuminate the interferometric modulators;

positioning a detector to receive light reflected from the interferometric modulators and produce a corresponding signal; and

coupling a computer to the detector, the computer configured receive the signal from the detector to determine, based on the signal, at least one response time parameters of the interferometric modulators during application of an actuation voltage or a release voltage, wherein the at least one parameter comprises one of the following;

a positive actuation response time (Tpa), a negative actuation response time (Tna), a positive release response time (Tpr), and a negative release response time (Tnr).

53. The method of claim 52, wherein each of the plurality of interferometric modulators comprises a fixed reflective surface and a movable reflective surface wherein the fixed reflective surface and the movable reflective surface are configured to cause interference of light.

54. A method of testing a plurality of interferometric modulators, the method comprising:

setting a time period during which to apply a switching voltage level, said switching voltage level being sufficient to change the interferometric modulators between a released state and an actuated state, or an actuated state and a released state;

applying a voltage waveform comprising the switching voltage level for the time period;

detecting light reflected from the interferometric modulators;

determining one or more response time parameters of the interferometric modulators based on said detecting; and

repeating said setting, applying, detecting, and determining step to identify a minimum time period during which a threshold value is achieved, the threshold value indicated a pre-determined number of pixels have actuated or released.

55. The method of claim 54, wherein the one or more response time parameters are based on the slowest actuation time of one or more interferometric modulators.

56. The method of claim 54, wherein the voltage applied to charge the state of the interferometric modulators is applied while the interferometric modulators are subject to a bias voltage.

57. The method of claim 54, wherein said detecting reflected light comprises visual analysis.

58. The method of claim 54, wherein said detecting reflected light comprises receiving the light in an optical system and measuring contrast.

59. The method of claim 54, wherein determining one or more response time parameters comprises determining an actuation response time.

60. The method of claim 54, wherein determining one or more response time parameters comprises determining a release response time.

61. The method of claim 54, wherein each of the plurality of interferometric modulators comprises a fixed reflective surface and a movable reflective surface wherein the fixed reflective surface and the movable reflective surface are configured to cause interference of light.

62. A system for testing a plurality of interferometric modulators, comprising:

a computer configured to determine a time period during which to apply a switching voltage level, said switching voltage level being sufficient to change a predetermined number of interferometric modulators between a released state and an actuated state, or an actuated state and a released state;

a voltage source controlled by said computer, said voltage source configured to apply a voltage waveform comprising the switching voltage level for the time period;

a light source positioned to illuminate the interferometric modulators; and

a detector positioned to receive light reflecting from the interferometric modulators and produce a signal corresponding to the received light,

wherein said computer is configured to receive the signal from the detector, and based on the signal, to iteratively vary the length of time for applying the voltage waveform to identify a minimum time period during which the number of pixels have actuated or released during the determined time period meets a threshold value, and to determine one or more response time parameters based on the identical minimum time period.

63. The system of claim 62, wherein the one or more response time parameters are based on the slowest actuation time or release time of one or more interferometric modulators.

64. The system of claim 62, wherein each of the plurality of interferometric modulators comprises a fixed reflective surface and a movable reflective surface wherein the fixed reflective surface and the movable reflective surface are configured to cause interference of light.

65. A system for testing a plurality of interferometric modulators, comprising:

means for determining a time period during which to apply a switching voltage level, said switching voltage level being sufficient to change the interferometric modulators between a non-actuated state and an actuated state, or an actuated state and a non-actuated state;

means for applying a controlled by said computer, said voltage source configured to apply a voltage waveform comprising the switching voltage level for the time period;

means for illuminating the interferometric modulators; and

means for sensing light reflected from the interferometric modulators and produce a signal corresponding to the received light,

wherein said determining means receives the signal from the sensing means and determines one or more response time parameters based on the signal, and said determining a time period means is further configured to iteratively control the application of a voltage waveform for a determined time period to identify a minimum time period where the number of pixels have actuated or released during the determined time period meets a threshold value.

66. The system of claim 65, wherein the one or more response time parameters are based on the slowest actuation time or release time of one or more interferometric modulators.

67. The system of claim 65, wherein said determining means comprises a computer.

68. The system of claim 65, wherein said applying means comprises a voltage source.

69. The system of claim 65, wherein said illuminating means comprises a light source.

70. The system of claim 65, wherein said sensing means comprises a photo detector.

71. The system of claim 65, wherein each of the plurality of interferometric modulators comprises a fixed reflective surface and a movable reflective surface wherein the fixed reflective surface and the movable reflective surface are configured to cause interference of light.

72. A method of manufacturing a system for testing a plurality of interferometric modulators, comprising:

providing a computer configured to determine a time period during which to apply a switching voltage level, said switching voltage level being sufficient to change the interferometric modulators between a released state and an actuated state, or an actuated state and a released state;

coupling a voltage source said computer, said voltage source configured to apply a voltage waveform comprising the switching voltage level for the time period;

positioning a light source to illuminate the interferometric modulators; and

positioning a detector to receive light reflecting from the interferometric modulators and produce a signal corresponding to the received light,

wherein said computer is configured to receive the signal from the detector, and based on the signal, to iteratively vary the length of time for applying the voltage waveform to identify a minimum time period during which the number of pixels have actuated or released during the determined time period meets a threshold value and to determine one or more response time parameters based on the identical minimum time period.

73. The method of claim 72, wherein each of the plurality of interferometric modulators comprises a fixed reflective surface and a movable reflective surface wherein the fixed reflective surface and the movable reflective surface are configured to cause interference of light.