Device and method for display memory using manipulation of mechanical response

• US 20060077505A1
• Filed: 04/22/2005
• Published: 04/13/2006
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Chui, Clarence, Kothari, Manish
• Granted Patent: US 7,626,581 B2
• Time in Patent Office: Days
• US Class Current: 359/239
• 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 2320/0252 Improving the response speed
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

Embodiments of an exemplary MEMS interferometric modulator comprise a movable layer and a fixed layer separated by an air gap. A driving scheme employs row/column actuation protocols which maintain voltages to the MEMS interferometric modulator that are above or below the voltage range necessary to place the MEMS interferometric modulator within a “hysteresis window” or “stability window.” Stable operation of the MEMS interferometric modulator is achieved by selecting mechanical design features that optimize the actuation and release times of the interferometric modulator. Some of the features affecting the release and actuation times include altering post spacing, altering internal stress or tension of the movable layer, altering the thickness or composition of the movable layer, altering the bulkiness of the tethers, perforating the movable layer and providing vias in the fixed layer.

Claims

1. A method of actuating an array of interferometric modulators multiple times to display a single frame of data, the method comprising:

receiving a data signal for actuating one or more interferometric modulators during a time period corresponding to a single frame;

actuating the interferometric modulator display element with a potential difference such that the interferometric modulator quickly moves to an actuation state;

releasing the interferometric modulator display element such that the interferometric modulator slowly drifts away from the actuation state and towards a released state; and

re-actuating the interferometric modulator display element such that before reaching the released state, the interferometric modulator quickly moves back to the actuation state.

2. The method of claim 1 further comprising applying a bias voltage to the interferometric modulator while the interferometric modulator drifts away from the actuation state.

3. The method of claim 2, wherein the potential difference is substantially equal to twice the bias voltage.

4. The method of claim 2, wherein an absolute value of the bias voltage is less than an absolute value of a voltage corresponding to a hysteresis window for the interferometric modulator display element.

5. A method of driving an interferometric modulator element to display a frame of data, the method comprising:

receiving a data signal for display by the interferometric modulator during a period of time corresponding to a single frame display period; and

periodically actuating the interferometric modulator display element during the single frame display period wherein the interferometric modulator quickly moves to an actuation state each time the interferometric modulator is actuated and moves slowly away from the actuation state when the potential difference is not applied.

6. The method of claim 5 further comprising applying a bias voltage to the interferometric modulator while the interferometric modulator moves slowly away from the actuation state.

7. The method of claim 6, wherein the potential difference is substantially equal to twice the bias voltage.

8. The method of claim 6, wherein an absolute value of the bias voltage is less than an absolute value of a voltage corresponding to a hysteresis window for the interferometric modulator display element.

9. A method of writing display data to a row of interferometric modulator display elements in an array of display elements, the method comprising:

writing a first set of display data to the row of the array with a potential difference so as to move at least some of the interferometric modulator elements to an actuated state;

releasing the interferometric modulator elements in the row of the array such that the interferometric modulator elements slowly drift away from the actuated state and towards the released state; and

re-writing the first set of display data to the row of the array with a potential difference so as to return the interferometric modulator elements to the actuated state before the interferometric modulators reach the released state.

10. The method of claim 9 further comprising applying a bias voltage to the interferometric elements in the row of the array while the interferometric modulators move slowly away from the actuated state.

11. The method of claim 10, wherein the potential difference is substantially equal to twice the bias voltage.

12. The method of claim 10, wherein an absolute value of the bias voltage is less than an absolute value of a voltage corresponding to a hysteresis window for the interferometric modulator elements.

13. A method of actuating an array of interferometric modulators multiple times to display a single frame of data, the method comprising:

receiving a data signal for actuating one or more interferometric modulators during a time period corresponding to a single frame;

actuating the interferometric modulator display element with a potential difference such that the interferometric modulator quickly moves to a released state;

releasing the interferometric modulator display element such that the interferometric modulator slowly drifts away from the released state and towards an actuated state; and

re-actuating the interferometric modulator display element such that before reaching the actuated state, the interferometric modulator quickly moves back to the released state.

14. The method of claim 13 further comprising applying a bias voltage to the interferometric modulator while the interferometric modulator drifts away from the released state.

15. The method of claim 14, wherein the potential difference is substantially equal to twice the bias voltage.

16. The method of claim 14, wherein an absolute value of the bias voltage is greater than an absolute value of a voltage corresponding to a hysteresis window for the interferometric modulator display element.

17. A method of driving an interferometric modulator element to display a frame of data, the method comprising:

receiving a data signal for display by the interferometric modulator during a period of time corresponding to a single frame display period; and

periodically actuating the interferometric modulator display element during the single frame display period wherein the interferometric modulator quickly moves to a released state each time the interferometric modulator is actuated and moves slowly away from the released state when the potential difference is not applied.

18. The method of claim 17 further comprising applying a bias voltage to the interferometric modulator while the interferometric modulator moves slowly away from the released state.

19. The method of claim 18, wherein the potential difference is substantially equal to twice the bias voltage.

20. The method of claim 18, wherein an absolute value of the bias voltage is greater than an absolute value of a voltage corresponding to a hysteresis window for the interferometric modulator display element.

21. A method of writing display data to a row of interferometric modulator display elements in an array of display elements, the method comprising:

writing a first set of display data to the row of the array with a potential difference so as to move at least some of the interferometric modulator elements to a released state;

actuating the interferometric modulator elements in the row of the array such that the interferometric modulator elements slowly drift away from the released state and towards the actuated state; and

re-writing the first set of display data to the row of the array with a potential difference so as to return the interferometric modulator elements to the released state before the interferometric modulators reach the actuated state.

22. The method of claim 21 further comprising applying a bias voltage to the interferometric elements in the row of the array while the interferometric modulators move slowly away from the released state.

23. The method of claim 22, wherein the potential difference is substantially equal to twice the bias voltage.

24. The method of claim 22, wherein an absolute value of the bias voltage is greater than an absolute value of a voltage corresponding to a hysteresis window for the interferometric modulator elements.