System and method of sensing actuation and release voltages of an interferometric modulator

• US 7,551,159 B2
• Filed: 01/28/2005
• Issued: 06/23/2009
• Est. Priority Date: 08/27/2004
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: IDC, LLC
• Inventors: Chui, Clarence, Mignard, Marc, Sampsell, Jeffrey B., Mathew, Mithran C.
• Primary Examiner(s): LEWIS, DAVID LEE
• Application Number:
  US11/045,865
• Publication Number:
  US 20060044298A1
• Time in Patent Office: 1,607 Days
• Field of Search: 345 55-100, 345108-109, 345204-214, 345/904, 324415-424
• US Class Current: 345/108
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81C 99/003 Characterising MEMS devices, e.g. measuring and identifying electrical or mechanical constants
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G02B 26/00 Optical devices or arrangements for the control of light using movable or deformable optical elements control of light by modification of the optical properties of the media of the elements involved therein G02F1/00
• 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 2300/0473 Use of light emitting or modulating elements having two or more stable states when no power is applied
• CPC Class Codes: G09G 2310/0278 Details of driving circuits arranged to drive both scan and data electrodes
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/12 Test circuits or failure detection circuits included in a display system, as permanent part thereof
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

A method for sensing the actuation and/or release voltages of a microelectromechanical device include applying a varying voltage to the device and sensing its state and different voltage levels. In one embodiment, the device is part of a system comprising an array of interferometric modulators suitable for a display. The method can be used to compensate for temperature dependent changes in display pixel characteristics.

Claims

1. A method of determining one or both of an actuation voltage and a release voltage of a microelectromechanical device, the method comprising:

applying at least two different electric potentials to at least one electrode coupled to said device;

detecting at least one capacitance dependent response of said device at said at least two different electric potentials;

determining, based at least in part on said response, a state of said device at said at least two different electric potentials; and

determining one or both of said actuation voltage and release voltage based at least in part on said determining a state of said device.

2. The method of claim 1, wherein said determining comprises determining whether said response is greater than a threshold.

3. The method of claim 2, wherein said detecting comprises sensing a voltage generated on said electrode.

4. The method of claim 2, wherein said detecting comprises sensing a current flow generated through said pixel.

5. A display system comprising:

an array of microelectromechanical pixels configured to present display data to a user of said display system;

at least one additional microelectromechanical pixel that is not one of said microelectromechanical pixels configured to present display data; and

a sensor, configured to sense an actuated state or a released state or both, of said at least one additional microelectromechanical pixel.

6. The display system of claim 5, wherein said sensor senses a capacitance dependent response of said additional microelectromechanical pixels.

7. The display system of claim 6, wherein said sensors comprise current sensors.

8. The system of claim 5, wherein at least some of said pixels configured to present display data comprise interferometric modulators.

9. The system of claim 5, wherein said sensor comprises a comparator.

16. The display system of claim 5, wherein said at least one additional micromechanical pixel is separate from said array of micromechanical pixels.

17. The display system of claim 5, wherein said at least one additional micromechanical pixel comprises two or more micromechanical pixels placed around the actual viewing are of the display.

18. The display system of claim 5, wherein said at least one additional micromechanical pixel is fabricated during the same process that produces said array such that the physical characteristics are similar if not essentially identical with the physical characteristics of the pixels in the viewable array.

19. The display system of claim 17, wherein some or all of the sense circuitry is shared among said two of more micromechanical pixels.

20. The display system of claim 17, where said at least one additional micromechanical pixel comprises four micromechanical pixels each being disposed near a corner of said array.

10. A method for compensating for shifts in one or both of the release and actuation voltage display pixels, the method comprising:

determining the actuation and or release state of at least one pixel; and

modifying driving voltage levels in response to said determining.

11. The method of claim 10, wherein said determining comprises determining the actuation and or release state of a test pixel.

12. A method of compensating for a temperature dependence of a display device, said method comprising determining one or both of an actuation and release voltage for at least one pixel associated with said display device and modifying device operational parameters based at least in part on said determining.

13. The method of claim 12, wherein said determining comprises determining a capacitance dependent electrical response of said at least one pixel.

14. The method of claim 12, wherein said at least one pixel comprises a test pixel that is not part of a viewable display.

15. A display device comprising:

an array of microelectromechanical pixels;

at least one test microelectromechanical pixel; and

means for determining one or both of an actuation voltage and release voltage of said test microelectromechanical pixel.

21. A display system comprising:

an array of microelectromechanical pixels configured to present display data to a user of said display system; and

a test circuit configured to apply at least two different electric potentials to at least one electrode coupled to a microelectromechanical pixel in said array, detect at least one capacitance dependent response of said device at said at least two different electric potentials, determine based at least in part on said response, a state of said device at said at least two different electric potentials, and determine one or both of said actuation voltage and release voltage based at least in part on said determining a state of said device.