Mirror actuator position sensor systems and methods

• US 7,075,700 B2
• Filed: 06/25/2004
• Issued: 07/11/2006
• Est. Priority Date: 06/25/2004
• Status: Expired due to Fees

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Muenter, Steven E.
• Primary Examiner(s): Mack, Ricky
• Assistant Examiner(s): CHOI, WILLIAM C
• Application Number:
  US10/877,592
• Publication Number:
  US 20050286111A1
• Time in Patent Office: 746 Days
• Field of Search: 359/231, 359/290, 359/291, 359/295, 359/298
• US Class Current: 359/291
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 26/0825 the reflecting element being a flexible sheet or membrane, e.g. for varying the focus flexible mirrors for cosmetic use A45D42/24
• CPC Class Codes: G02B 7/185 with means for adjusting the shape of the mirror surface

Abstract

Systems and methods are disclosed herein to provide position information, such as for example via a mirror actuator position sensor. For example, in accordance with an embodiment of the present invention, a mirror actuator is disclosed which utilizes its own capacitance to directly sense and provide mirror position information. The mirror position information may be utilized as a position feedback signal to assist in controlling a position of the mirror.

Claims

1. A mirror system comprising:

a mirror;

a mirror actuator circuit having an electrode to control a position of the mirror, wherein a capacitance between the electrode and the mirror is measured to determine a position of the mirror, and wherein the mirror actuator circuit comprises;

an amplifier circuit adapted to provide a first voltage signal to the electrode to provide an electrostatic force to control the position of the mirror;

a measurement circuit adapted to measure the capacitance between the electrode and the mirror and provide a measured mirror position signal;

a difference circuit adapted to receive a mirror position command and the measured mirror position signal and provide a mirror position error signal to the amplifier circuit; and

a memory adapted to store linearized values to provide to the difference circuit based on the measured mirror position signal to compensate for non-linear relationships.

2. The mirror system of claim 1, wherein the mirror is a micro-electro-mechanical system mirror membrane.

3. The mirror system of claim 1, wherein the capacitance measured is converted to the mirror position error signal to control a position of the mirror.

4. The mirror system of claim 1, wherein the mirror actuator circuit further comprises a resistor coupled between the amplifier circuit and the measurement circuit.

5. The mirror system of claim 1, wherein the measurement circuit comprises a charge amplifier circuit, a relaxation oscillator, or an impedance bridge.

6. The mirror system of claim 1, wherein the measurement circuit further comprises a high frequency signal generator adapted to provide a high frequency signal to the mirror.

7. The mirror system of claim 1, wherein the mirror system further comprises a plurality of the mirrors and corresponding ones of the mirror actuator circuits, the electrodes forming an electrode array for the mirror.

8. The mirror system of claim 1, wherein the mirror system is incorporated as pan of an adaptive optic system or an optical correction system.

9. A mirror actuator system comprising:

a mirror;

a plurality of electrodes associated with the mirror; and

a plurality of mirror actuator circuits corresponding to the plurality of electrodes, the mirror actuator circuits adapted to provide a corresponding first signal to the corresponding electrodes to control a position of the mirror and further adapted to measure a corresponding capacitance between the corresponding electrodes and the mirror to provide a corresponding measured mirror position;

wherein the mirror actuator circuits each comprises;

an amplifier adapted to provide a high voltage signal to the electrode to generate an electrostatic force to act on the mirror;

a capacitance measurement circuit adapted to measure the capacitance between the electrode and the mirror and provide a measured mirror position signal;

an isolation capacitor adapted to isolate the amplifier from the capacitance measurement circuit; and

a feedback circuit adapted to compare the measured mirror position signal and a mirror position command and provide a mirror position error signal to the amplifier.

10. The mirror actuator system of claim 9, wherein the measured mirror positions provide feedback to correct for corresponding position errors of the mirror.

11. The mirror actuator system of claim 9, wherein the measured mirror positions are compensated for a non-linear relationship between the capacitance and the corresponding measured mirror position.

12. The mirror actuator system of claim 9, wherein the capacitance measurement circuit comprises a charge amplifier circuit, a relaxation oscillator, or an impedance bridge.

13. The mirror actuator system of claim 9, wherein the feedback circuit is further adapted to compensate for a non-linear relationship between the capacitance measured and the measured mirror position signal.

14. The mirror actuator system of claim 9, wherein the mirror actuator system further comprises a signal generator adapted to generate a signal on the mirror to facilitate the capacitance to be measured between each of the electrodes and the mirror.

15. The mirror actuator system of claim 9, wherein the mirror actuator system is formed as part of an adaptive optic system or an optical correction system.

16. A method of determining a position of a mirror, the method comprising:

providing an electrostatic actuator adapted to control a position of the mirror;

providing a drive signal to the electrostatic actuator to control the position of the mirror;

measuring a capacitance between the electrostatic actuator and the mirror;

isolating the providing of the drive signal from the measuring of the capacitance;

converting the capacitance measured to a measured mirror position;

comparing the measured mirror position to a commanded mirror position to generate a position error;

providing the position error as a feedback signal for the providing of the drive signal to correct the position error of the mirror; and

storing linearized values to compensate the measured mirror position for a non-linear relationship between the capacitance measured and the measured mirror position.

17. The method of claim 16, wherein the measuring of the capacitance further comprises providing an alternating current signal on the mirror for the measuring of the capacitance.

18. The method of claim 16, further comprising compensating the position error for a non-linear relationship between the capacitance measured and the measured mirror position.

19. The method of claim 16, wherein the electrostatic actuator controls an electrostatic force acting on the mirror.

20. The method of claim 16, wherein the providing of the drive signal occurs approximately simultaneously with the measuring of the capacitance.