Systems and methods of actuating MEMS display elements

• US 8,085,461 B2
• Filed: 05/15/2009
• Issued: 12/27/2011
• Est. Priority Date: 09/27/2004
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Gally, Brian J., Cummings, William J.
• Primary Examiner(s): Sugarman, Scott J
• Assistant Examiner(s): TRA, TUYEN Q
• Application Number:
  US12/467,130
• Publication Number:
  US 20090219600A1
• Time in Patent Office: 956 Days
• Field of Search: 359/245, 359/267, 359/290, 359/291, 359/292, 359/223, 359/224
• US Class Current: 359/290
• 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 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

Apparatus and methods of actuating MEMS display elements are disclosed. The disclosed embodiments can be incorporated into other drive schemes for MEMS display elements. In one embodiment, an apparatus for controlling a MEMS display element to display a frame of video data, said MEMS display element comprising a portion of an array of MEMS display elements, includes an array controller configured to assert a potential difference on said MEMS display element during a first portion of a frame display write process to place the MEMS display element in a first display state, and to assert a potential difference on said MEMS display element during a second portion of the frame display write process to place the MEMS display element in a second display state to display the frame of the video data, where the first display state is different from the second display state. In another embodiment, an array controller asserts a large potential difference across a MEMS display element to affect charge build up and an offset voltage level. In another embodiment, an array controller asserts a series of pulses to rapidly switch the MEMS display element between states to overcome adverse conditions that may affect the operation of the MEMS display element.

Claims

1. A method of operating a MEMS display element, said MEMS display element displaying bistability arising from a hysteresis curve having actuation and relaxation portions, said method comprising:

producing a shift of said hysteresis curve by applying a series of actuation voltages to said MEMS display element during operation of a display incorporating said MEMS display element; and

applying a restoring voltage to said MEMS display element, said restoring voltage having a magnitude larger than said series of actuation voltages and being sufficient to reduce said shift of said hysteresis curve.

2. The method of claim 1, wherein said restoring voltage comprises a large amplitude positive potential followed by a large amplitude negative potential.

3. The method of claim 1, wherein said restoring voltage comprises a large amplitude negative potential followed by a large amplitude positive potential.

4. The method of claim 1, wherein said restoring voltage comprises an AC waveform toggling between a large amplitude positive potential and a large amplitude negative potential.

5. The method of claim 1, wherein said MEMS display element comprises an interferometric modulator.

6. The method of claim 1, wherein said restoring voltage is more than about 1.25 times the potential of said series of actuation potentials.

7. The method of claim 1, wherein said restoring voltage is more than about 1.5 times the potential of said series of actuation potentials.

8. The method of claim 1, wherein said restoring voltage is more than about 2.0 times the potential of said series of actuation potentials.

9. The method of claim 1, wherein said restoring voltage has a polarity opposite to a pre-existing charge buildup.

10. The method of claim 1, wherein said applying is performed at predetermined times.

11. A display apparatus, comprising:

at least one MEMS display element displaying bistability arising from a hysteresis curve having actuation and relaxation portions; and

an array controller is operable for producing a shift of said hysteresis curve by;

applying a series of actuation voltages to said MEMS display element during operation of a display incorporating said MEMS display element; and

applying a restoring voltage to said MEMS display element, said restoring voltage having a magnitude larger than said series of actuation voltages and being sufficient to reduce said shift of said hysteresis curve.

12. The apparatus of claim 11, wherein said restoring voltage comprises a large amplitude positive potential followed by a large amplitude negative potential.

13. The apparatus of claim 11, wherein said restoring voltage comprises a large amplitude negative potential followed by a large amplitude positive potential.

14. The apparatus of claim 11, wherein said restoring voltage comprises an AC waveform toggling between a large positive potential and a large negative potential.

15. The apparatus of claim 11, wherein said MEMS display element comprises an interferometric modulator.

16. The apparatus of claim 11, wherein said restoring voltage is more than about 1.25 times the potential of said series of actuation potentials.

17. The apparatus of claim 11, wherein said restoring voltage is more than about 1.5 times the potential of said series of actuation potentials.

18. The apparatus of claim 11, wherein said restoring voltage is more than about 2.0 times the potential of said series of actuation potentials.

19. The apparatus of claim 11, wherein said restoring voltage has a polarity opposite to a pre-existing charge buildup.

20. The apparatus of claim 11, wherein said applying is performed at predetermined times.

21. The apparatus of claim 11, further comprising:

a display comprising said at least one MEMS display element;

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.

22. The apparatus of claim 21, 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.

23. The apparatus of claim 21, further comprising an image source module configured to send said image data to said processor.

24. The apparatus of claim 23, wherein said image source module comprises at least one of a receiver, transceiver, and transmitter.

25. The apparatus of claim 21, further comprising an input device configured to receive input data and to communicate said input data to said processor.

26. A display apparatus comprising:

means for modulating light in a display, said modulating means displaying bistability arising from a hysteresis curve having actuation and relaxation portions;

means for applying a series of actuation voltages to said modulating means to produce a shift of said hysteresis curve during operation of said display incorporating said modulating means; and

means for applying a restoring voltage to said modulating means, said restoring voltage having a magnitude larger than said series of actuation voltages and being sufficient to reduce said shift of said hysteresis curve.

27. The apparatus of claim 26, wherein said modulating means comprises at least one MEMS display element.

28. The apparatus of claim 26, wherein said applying a series of actuation voltages means comprises an array controller.

29. The apparatus of claim 26, wherein said applying a restoring voltage means comprises an array controller.