Analog interferometric modulator

• US 8,619,350 B2
• Filed: 06/27/2011
• Issued: 12/31/2013
• Est. Priority Date: 06/15/2009
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Lee, Chong U., Hong, John H., Mignard, Marc M., Govil, Alok
• Primary Examiner(s): Ben, Loha
• Application Number:
  US13/169,947
• Publication Number:
  US 20110255143A1
• Time in Patent Office: 918 Days
• Field of Search: 359/245, 359290-295, 359/298, 345/108, 345/212, 257/20, 430/35, 315/411, 324/511
• US Class Current: 359/245
• 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 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

Methods and devices for calibrating and controlling the actuation of an analog interferometric modulator configured to have a plurality of actuation states. Devices and methods for calibrating an analog interferometric modulator to respond in linear relation to an applied voltage.

Claims

1. A device for modulating light, comprising:

a first layer;

a second layers, wherein a gap is present between the first and second layer and the first layer and the second layer are stationary relative to each other;

a third layer disposed in the gap between the first and second layer;

a control circuit configured to selectively induce an electric field between the first and second layers by applying a bias voltage across the first layer and the second layer; and

a charge pump configured to apply a fixed charge to the third layer;

wherein the third layer is electrically isolated after the fixed charge is applied, and

wherein the control circuit is configured to cause the third layer to move within the gap by varying the bias voltage, wherein movement of the third layer is based on an electrostatic force between the electric field and the fixed charge applied to the third layer and a mechanical restorative force acting on the third layer.

2. The device of claim 1, wherein at least one resistive element is disposed on the bottom of the first layer.

3. The device of claim 1, further comprising a switch for electrically isolating the third layer.

4. The device of claim 1, further comprising a thin film semiconductor or MEMS switch for electrically isolating the third layer.

5. The device of claim 1, wherein the third layer comprises an optical minor.

6. The device of claim 1, wherein the second layer comprises a thin optical absorber.

7. The device of claim 1, wherein the control circuit is configured to apply a first voltage as the bias voltage when the device is in a calibration mode.

8. The device of claim 7, wherein subsequent to the first voltage being applied, the electrostatic force is approximately equal to the mechanical restorative force.

9. The device of claim 2, wherein the control circuit is configured to apply a first voltage as the bias voltage when the device is in calibration mode, wherein the third layer contacts the resistive element of the first layer subsequent to the first voltage being applied.

10. The device of claim 1, wherein the third layer is configured to move in linear proportion to the bias voltage.

11. A method of calibrating an analog interferometric modulator, comprising:

providing a first electrode and a second electrode, wherein a gap is present between the first electrode and the second electrode;

applying a bias voltage across the first electrode and the second electrode to induce an electric field between the first electrode and the second electrode;

inducing a fixed charge on a third electrode, wherein the third electrode is electrically isolated after the fixed charge is applied; and

moving the third electrode within the gap by varying the bias voltage, wherein movement of the third electrode is based on an electrostatic force between the electric field and the fixed charge applied to the third electrode and a mechanical restorative force acting on the third electrode.

12. The method of claim 11, further comprising determining an amount of fixed charge comprising:

providing at least one resistive element disposed on the first electrode;

applying a calibration voltage as the bias voltage to the first electrode and second electrode; and

adjusting the fixed charge on the third electrode such that the electric field induced by the calibration voltage causes the third electrode to contact the at least one resistive element of the first electrode.

13. The method of claim 11, further comprising adjusting the fixed charge on the third electrode such that the electrostatic force about equals the mechanical restorative force.

14. The method of claim 11, wherein the inducing comprises inducing the fixed charge on the third electrode such that the displacement of the third electrode responds in linear proportion to the bias voltage.

15. A device for modulating light, comprising:

first means for conducting current;

second means for conducting current, wherein a gap is present between the first conducting means and the second conducting means;

means for applying a bias voltage across the first conducting means and the second conducting means to induce an electric field between the first conducting means and the second conducting means; and

means for inducing a fixed charge on a third means for conducting current,

wherein the third means for conducting current is electrically isolated after the fixed charge is applied, and

wherein the means for applying a bias voltage is configured to cause the third means for conducting current to move within the gap by varying the bias voltage, wherein movement of the third means for conducting current is based on an electrostatic force between the electric field and the fixed charge applied to the third means for conducting current and a mechanical restorative force acting on the third means for conducting current.

16. The device of claim 15, wherein the applying means comprises a control circuit.

17. The device of claim 15, wherein the inducing means comprises a charge pump.

18. The device of claim 15, further comprising a means for electrically isolating the third conducting means.

19. The device of claim 18, wherein the means for electrically isolating comprises a switch.

20. The device of claim 18, wherein the means for electrically isolating comprises a thin film semiconductor.

21. The device of claim 15, wherein an insulating layer is disposed on the top of the second conducting means.

22. The device of claim 15, wherein a stiffening layer is disposed on the third conducting means.

23. The device of claim 15, wherein a capacitor is in communication with the third conducting means.

24. The device of claim 15, wherein the first conducting means comprises an electrode, the second conducting means comprises an electrode, and the third conducting means comprises an electrode.

25. The device of claim 15, wherein means for inducing is further configured to induce the charge on the third means for conducting current such that movement of the third conducting means is in linear proportion to the bias voltage.