Methods for visually inspecting interferometric modulators for defects

• US 7,415,186 B2
• Filed: 09/01/2005
• Issued: 08/19/2008
• 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.
• Primary Examiner(s): CONNELLY CUSHWA, MICHELLE R
• Application Number:
  US11/217,580
• Publication Number:
  US 20060067652A1
• Time in Patent Office: 1,083 Days
• Field of Search: None
• US Class Current: 385/147
• 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 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

A method is provided for visual inspection of an array of interferometric modulators in various driven states. This method may include driving multiple columns or rows of interferometric modulators via a single test pad or test lead, and then observing the array for discrepancies between the expected optical output and the actual optical output of the array. This method may particularly include, for example, driving a set of non-adjacent rows or columns to a state different from the intervening rows or columns, and then observing the optical output of the array.

Claims

1. A method of testing an array of interferometric modulators, the method comprising:

applying a first signal at least partly contemporaneously to a first plurality of non-adjacent columns of interferometric modulators to place the interferometric modulators in said first plurality of non-adjacent columns in an actuated state, wherein said first signal comprises at least one hold time signal portion, the hold time signal portion comprising voltages alternating between positive and negative voltage levels, the positive and negative voltage levels having magnitudes that do not result in a change of state of the interferometric modulators in said first plurality of non-adjacent columns; and

inspecting said array of interferometric modulators to identify defects in said array, wherein said inspecting is performed after application of said first signal.

2. The method of claim 1, additionally comprising:

applying a second signal at least partly contemporaneously to said first plurality of non-adjacent columns to place the interferometric modulators in said first plurality of non-adjacent columns in an unactuated state;

applying a third signal at least partly contemporaneously to a second plurality of non-adjacent columns of interferometric modulators to place the interferometric modulators in said second plurality of non-adjacent columns in an unactuated state, wherein said first signal is applied after said second and third signals.

3. The method of claim 2, additionally comprising:

applying a fourth signal at least partly contemporaneously to a third plurality of non-adjacent columns of interferometric modulators to place the interferometric modulators in said third plurality of non-adjacent columns in an unactuated state, wherein each of the modulators in the third plurality of columns are configured to reflect light of a substantially similar color when said modulators are in an unactuated state, and wherein said fourth signal is applied prior to said first signal; and

applying a fifth signal at least partly contemporaneously to said second plurality of non-adjacent columns of interferometric modulators to place the interferometric modulators in said second plurality of non-adjacent columns in an actuated state, wherein said fifth signal is applied after said second, third and fourth signals.

4. The method of claim 1, additionally comprising applying a second signal at least partly contemporaneously to a second plurality of columns of interferometric modulators in the array to place the modulators in said second array of columns in an actuated state, wherein the second plurality of columns comprises every column in said array of interferometric modulators except for said first plurality of columns.

5. The method of claim 4, wherein said first signal is substantially identical to said second signal.

6. The method of claim 4, additionally comprising applying a third signal at least partly contemporaneously to all columns of interferometric modulators in said array to place all modulators in said array in an unactuated state, wherein said third signal is applied before said first and second signals.

7. The method of claim 1, wherein a diffuser layer is placed between an observer and said array prior to inspecting said array of interferometric modulators.

8. The method of claim 1, wherein inspecting the array of interferometric modulators comprises identifying the locations of any visible defects.

9. The method of claim 1, comprising inspecting said array during application of the hold-time signal portion.

10. The method of claim 1, wherein the positive voltage level of the hold time signal is between a positive release voltage and a positive actuation voltage, and the negative voltage level of the hold time signal is between a negative release voltage and a negative actuation voltage.

11. A method of testing an array of interferometric modulators, the method comprising:

applying a first waveform at least partly contemporaneously to each of a first plurality of non-adjacent rows of interferometric modulators;

applying a second waveform at least partly contemporaneously to each of a second plurality of non-adjacent rows of interferometric modulators;

applying a third waveform at least partly contemporaneously to each of a first plurality of non-adjacent columns of interferometric modulators;

applying a fourth waveform at least partly contemporaneously to each of a second plurality of non-adjacent columns of interferometric modulators; and

inspecting said array of interferometric modulators to identify defects in the array,

wherein at least one of said first, second, third and fourth waveforms is configured to place the corresponding plurality of non-adjacent rows and/or columns of interferometric modulators in a predetermined state, and at least one of said first, second, third and fourth signal waveforms comprises at least one hold time signal portion, the hold time signal portion comprising voltages alternating between positive and negative voltage levels, the positive and negative voltage levels having magnitudes that do not result in a change of state of the interferometric modulators.

12. The method of claim 11, wherein said first and second pluralities of non-adjacent columns comprise every column in the array, and wherein said first and second pluralities of non-adjacent rows comprise every row in the array.

13. The method of claim 11, wherein said interferometric modulators in said first plurality of non-adjacent columns comprise interferometric modulators that are larger than said interferometric modulators in said second plurality of non-adjacent columns.

14. The method of claim 13 wherein the interferometric modulators in said first plurality of non-adjacent columns comprise interferometric modulators which have a larger viewable area than the interferometric modulator elements in said second plurality of non-adjacent columns.

15. The method of claim 11, wherein said third waveform comprises a first signal which places each modulator in said first plurality of non-adjacent columns in a first state.

16. The method of claim 15, wherein said fourth waveform comprises a first signal which places each modulator in said second plurality of non-adjacent columns in the first state.

17. The method of claim 11, wherein said first waveform comprises a first signal which places a first plurality of non-adjacent modulators within said first plurality of non-adjacent columns in a first state.

18. The method of claim 17, wherein said second waveform comprises a second signal which places a second plurality of non-adjacent modulators within said first plurality of non-adjacent columns in said first state.

19. The method of claim 17, wherein said second waveform comprises a second signal which places a first plurality of non-adjacent modulators within said second plurality of non-adjacent columns in said first state.

20. The method of claim 11, additionally comprising applying a fifth waveform at least partly contemporaneously to each of a third plurality of non-adjacent columns of interferometric modulators.

21. The method of claim 20, wherein each of the modulators in the third plurality of columns of interferometric modulators are configured to reflect light of about the same color.

22. The method of claim 20, wherein said first, second, and third pluralities of non-adjacent columns comprise every column in the array, and wherein said first and second pluralities of non-adjacent rows comprise every row in the array.

23. The method of claim 11, additionally comprising placing a diffuser adjacent the array of interferometric modulators.

24. The method of claim 11, comprising inspecting said array during application of the hold-time signal portion.

25. The method of claim 11, wherein the magnitudes of the alternating positive and negative voltages of the hold-time signal portion are greater than a release voltage magnitude and less than an actuation voltage magnitude.

26. A method of inspecting an array of interferometric modulators, comprising:

driving each modulator in the array of interferometric modulators to a known first state;

driving a subset of columns of interferometric modulators within the array from said known first state to a second state, wherein said second state is the opposite of said first state;

applying a hold-time signal to at least the subset of columns of interferometric modulators, wherein said hold time signal comprises voltages alternating between positive and negative voltage levels, the positive and negative voltage levels having magnitudes that do not result in a change of state of the subset of columns of interferometric modulators; and

inspecting said array of interferometric modulators to identify defects in the array.

27. The method of claim 26, wherein the known first state is a bright state, and wherein the second state is a dark state.

28. The method of claim 26, additionally comprising:

driving each modulator in the array back to said known first state; and

driving a second subset of columns of interferometric modulators within the array from said known first state to said second state.

29. The method of claim 28, additionally comprising:

driving each modulator in the array back to said known first state; and

driving a third subset of columns of interferometric modulators within the array from said known first state to said second state.

30. The method of claim 26, additionally comprising:

driving each modulator in the array to a known third state; and

driving a subset of rows of interferometric modulators within the array to a fourth state, wherein said fourth state is the opposite of said third state.

31. The method of claim 30, wherein said known third state is a bright state, and wherein said fourth state is a dark state.

32. The method of claim 30, additionally comprising:

driving each modulator in the array back to said known third state; and

driving a second subset of rows of interferometric modulators within the array to said known fourth state.

33. The method of claim 26, additionally comprising:

driving each of the modulators in the array to a known fifth state; and

driving each of the modulators in the array to a sixth state, wherein the sixth state is the opposite of the known fifth state.

34. The method of claim 33, wherein the known fifth state is a bright state and wherein the sixth state is a dark state.

35. The method of claim 26, wherein the array is formed on a substrate having a viewer side and a process side, the array being formed on the process side of the substrate.

36. The method of claim 35, additionally comprising placing a diffuser layer adjacent the viewer side of the substrate.

37. The method of claim 35, additionally comprising placing the substrate within a probe mount prior to driving the array.

38. The method of claim 26, comprising inspecting said array during application of the hold-time signal portion.

39. The method of claim 26, wherein the positive voltage level of the hold time signal is between a positive release voltage and a positive actuation voltage, and the negative voltage level of the hold time signal is between a negative release voltage and a negative actuation voltage.