Optimized electronic operation of digital micromirror devices

• US 5,444,566 A
• Filed: 03/07/1994
• Issued: 08/22/1995
• Est. Priority Date: 03/07/1994
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Cleveland, Harlan P., Lawson, Randall S., Gale, Richard O., Davis, Carl W., Tew, Claude E., Chu, Henry, Heimbuch, Scott D.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US08/206,812
• Time in Patent Office: 533 Days
• Field of Search: 359/224, 359/230, 359/291, 359/298
• US Class Current: 359/291
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: Y10S 359/904 Micromirror

Abstract

A method for controlling a digital micromirror device 40 resulting in decreased mechanical stress, longer device lifetimes, decreased incidence of spontaneous bit reset, and increased pulse-width modulation accuracy. To reduce the device stress, the bias voltage 142 applied to the mirror 50 may be reduced after the mirror 50 has been latched. To prevent premature mirror changes, the address electrode bias voltage 140 may be reduced after the mirror is driven to the desired position. To ensure that the mirror 50 returns to the neutral position during reset, the mirror bias voltage 142 may be raised from ground potential to approximately halfway between the two addressing voltages during the reset period 152. To reduce the effects of hinge memory and to ensure that the mirror 50 rotates toward the proper address electrode, the mirror bias voltage 142 may be gradually increased to allow the mirror 50 time to rotate towards the proper address electrode.

Claims

1. A method of resetting a digital micromirror device comprising:

biasing a pair of address electrodes of a digital micromirror device element, wherein a first voltage is applied to a first address electrode and a second voltage is applied to a second address electrode; and

biasing a deflectable structure with a third voltage, wherein said third voltage is less than said first voltage and greater than said second voltage.

2. The method of claim 1 wherein said third voltage is approximately halfway between said first voltage and said second voltage.

3. The method of claim 1 further comprising the step of changing the bias of said deflectable structure from said third voltage to a fourth voltage thereby increasing the deflection of said deflectable structure.

4. The method of claim 3 wherein said fourth voltage causes said deflectable structure to be deflected against a landing electrode.

5. The method of claim 4 further comprising the step of reducing the bias of said deflectable structure from said fourth voltage to a fifth voltage.

6. The method of claim 1 wherein said first voltage is increased thereby increasing the deflection of said deflectable structure.

7. A method of operating a digital micromirror device comprising:

biasing a pair of address electrodes of a digital micromirror device element, wherein a first voltage is applied to a first address electrode and a second voltage is applied to a second address electrode;

biasing a deflectable structure with a third voltage; and

increasing the bias applied to said first address electrode from said first voltage to a fourth voltage thereby increasing the deflection of said deflectable structure.

8. The method of claim 7 wherein said third voltage is less than said first voltage and greater than said second voltage.

9. The method of claim 7 wherein said third voltage is approximately halfway between said first voltage and said second voltage.

10. The method of claim 7 further comprising the step of changing the bias of said deflectable structure from said third voltage to a fifth voltage thereby increasing the deflection of said deflectable structure.

11. The method of claim 10 wherein said fifth voltage causes said deflectable structure to be deflected against a landing electrode.

12. The method of claim 11 further comprising the step of reducing the bias of said deflectable structure from said fifth voltage to a sixth voltage.

13. The method of claim 12 wherein said deflectable structure remains in contact with said landing electrode after said bias is reduced to said sixth voltage.

14. A method of operating a digital micromirror device comprising:

biasing a pair of address electrodes of a digital micromirror device element, wherein a first voltage is applied to a first address electrode and a second voltage is applied to a second address electrode;

biasing a deflectable structure with a third voltage; and

changing the bias applied to said deflectable structure gradually from said third voltage to a fourth voltage thereby increasing the deflection of said deflectable structure.

15. The method of claim 14 wherein said changing step comprises ramping the bias applied to said deflectable structure from said third voltage to said fourth voltage.

16. The method of claim 14 wherein said changing step comprises stepping the bias applied to said deflectable structure from said third voltage to said fourth voltage in at least two discrete steps.

17. A method of biasing a digital micromirror device comprising:

applying a first bias voltage to a deflectable structure, wherein said first bias voltage is greater than a minimum voltage required to deflect said deflectable structure to a limiting position;

reducing said first bias voltage to a second bias voltage after said deflectable structure is driven to said limiting position, wherein the magnitude of said second bias voltage is less than the magnitude of said first bias voltage.

18. The method of claim 17 wherein said first bias voltage and said second bias voltage are negative voltages.

19. The method of claim 17 wherein said first bias voltage and said second bias voltage are positive voltage.