Damped control of a micromechanical device

• US 6,891,657 B2
• Filed: 12/31/2003
• Issued: 05/10/2005
• Est. Priority Date: 05/20/2003
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hewlett, Gregory J., McDonald, William C.
• Primary Examiner(s): Sugarman, Scott J.
• Assistant Examiner(s): Dinh, Jack
• Application Number:
  US10/749,469
• Publication Number:
  US 20040233506A1
• Time in Patent Office: 496 Days
• Field of Search: 359/290, 359/291, 359/296, 359/298, 359/212, 359/214, 359/223, 359/224, 359/295, 359/230
• US Class Current: 359/291
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

Device and method for a damping function to reduce undesirable mechanical transient responses to control signals. In one aspect of the present invention, the damping function may be used to reduce overshoot and oscillation when a digital micromirror is driven from a landing plate to the flat or neutral position. In another aspect of the present invention, the damping function may be used to reduce transient resonance of a digital micromirror when the micromirror is driven to a landing plate.

Claims

1. A method of operating a digital micromirror device having at least one micromirror, the method comprising:

applying a reset voltage pulse to the micromirror, wherein the reset voltage pulse causes the micromirror to launch from a landing plate;

applying an offset voltage to the micromirror immediately after the reset voltage pulse, wherein the offset voltage is applied for a damping delay period, wherein the micromirror launches and is moving away from the landing plate before an expiration of the damping delay period;

applying a damping pulse to the micromirror immediately after the offset voltage, wherein the damping pulse voltage is equal to a bias voltage for the micromirror; and

reapplying the offset voltage to the micromirror, whereby the damping pulse reduces oscillation of the micromirror about a neutral position.

2. The method of claim 1, wherein a damping pulse polarity is opposite from a reset voltage pulse polarity.

3. The method of claim 2, wherein the damping pulse has a positive polarity and the reset voltage pulse has a negative polarity.

4. The method of claim 1, further comprising:

loading an address state for the micromirror during the reapplying of the offset voltage; and

applying the bias voltage to the micromirror, wherein the micromirror assumes the address state.

5. The method of claim 1, wherein the reset voltage is about −

26 volts, the offset voltage is about 7 volts, and the bias voltage is about 24 volts.

6. The method of claim 1, wherein the damping delay period is greater than 1 microsecond.

7. The method of claim 6, wherein the damping delay period is about 1.6 microseconds and the damping pulse is about 3.9 microseconds long.

8. A method of operating a digital micromirror device having at least one micromirror, the method comprising:

applying a reset voltage pulse to the micromirror, wherein the reset voltage pulse causes the micromirror to launch from a landing plate;

applying an offset voltage to the micromirror immediately after the reset voltage pulse, wherein the offset voltage is applied for a damping delay period, wherein the micromirror launches and is moving away from the landing plate before an expiration of the damping delay period;

applying a damping pulse to the micromirror immediately after the offset voltage, wherein the damping pulse polarity is opposite to the reset voltage polarity; and

reapplying the offset voltage to the micromirror, whereby the damping pulse reduces oscillation of the micromirror about a neutral position.

9. The method of claim 8, wherein the damping pulse has a positive polarity and the reset voltage pulse has a negative polarity.

10. The method of claim 8, further comprising:

loading an address state for the micromirror during the reapplying of the offset voltage; and

applying the bias voltage to the micromirror, wherein the micromirror assumes the address state.

11. The method of claim 10, wherein the reset voltage is about −

26 volts, the offset voltage is about 7 volts, and the bias voltage is about 24 volts.

12. The method of claim 8, wherein the damping delay period is greater than 1 microsecond.

13. The method of claim 12, wherein the damping delay period is about 1.6 microseconds and the damping pulse is about 3.9 microseconds long.