METHODS FOR MEASUREMENT AND CHARACTERIZATION OF INTERFEROMETRIC MODULATORS

• US 20090201009A1
• Filed: 09/30/2008
• Published: 08/13/2009
• Est. Priority Date: 02/11/2008
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Govil, Alok
• Granted Patent: US 8,395,371 B2
• Time in Patent Office: Days
• US Class Current: 324/76.390
• CPC Class Codes: G01R 31/2637 for testing other individual devices G01R31/2608 - G01R31/2632, G01R31/27 take precedence
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

Various methods are described to characterize interferometric modulators or similar devices. Measured voltages across interferometric modulators may be used to characterize transition voltages of the interferometric modulators. Measured currents may be analyzed by integration of measured current to provide an indication of a dynamic response of the interferometric modulator. Frequency analysis may be used to provide an indication of a hysteresis window of the interferometric modulator or mechanical properties of the interferometric modulator. Capacitance may be determined through signal correlation, and spread-spectrum analysis may be used to minimize the effect of noise or interference on measurements of various interferometric modulator parameters.

Claims

1. A method of characterizing the behavior of a microelectromechanical system (MEMS) device, the method comprising:

applying a sinusoidal voltage signal to the MEMS device, wherein the MEMS device comprises a movable electrode spaced apart from another electrode;

measuring an output signal;

identifying frequency components of the output signal; and

determining whether the frequency components of the output signal are indicative of non-linear behavior of the MEMS device.

2. The method of claim 1, wherein the output signal is indicative of the electrical characteristics of the MEMS device

3. The method of claim 1, wherein the output signal comprises current through the MEMS device.

4. The method of claim 1, wherein determining whether the frequency components of the output signal are indicative of non-linear behavior of the MEMS device comprises determining whether at least a portion of the sinusoidal voltage falls within a hysteresis window of the MEMS device.

5. The method of claim 1, wherein identifying the frequency components of the output signal comprises performing a Fourier transform of the output signal.

6. The method of claim 1, further comprising identifying a transition voltage of the MEMS device based upon the presence of non-linear behavior.

7. The method of claim 6, wherein identifying a transition voltage of the MEMS device comprises applying at least a second sinusoidal voltage signal to the MEMS device, wherein the second sinusoidal voltage spans a voltage range different from the voltage range of the first sinusoidal voltage.

8. A method of identifying transition voltages of a microelectromechanical system (MEMS) device, the method comprising:

consecutively applying a plurality of sinusoidal voltage signals to the MEMS device, wherein the voltage ranges spanned by each of the plurality of sinusoidal voltage signals are different from one another;

measuring a current through the MEMS device in response to each of the plurality of sinusoidal voltage signals;

identifying frequency components of the measured current; and

determining whether the range of one of the plurality of voltage signals comprises a transition voltage based upon the frequency components of the measured current in response to the application of said one of the plurality of voltage signals.

9. The method of claim 8, wherein identifying the frequency components of the measured current comprises performing a Fourier transform of the measured current.

10. The method of claim 8, wherein the MEMS device comprises a movable layer and a fixed layer.

11. The method of claim 10, wherein determining whether the range of said one of the plurality of voltage signals comprises a transition voltage comprises identifying an actuation or release voltage of the MEMS device.

12. The method of claim 8, wherein the MEMS device comprises an interferometric modulator.

13. A device, comprising:

a microelectromechanical system (MEMS) device comprising a movable layer;

circuitry configured to apply a sinusoidal voltage signal to the MEMS device, measure a current through the MEMS device;

identify frequency components of the measured current; and

determine whether the frequency components of the measured current are indicative of non-linear behavior of the MEMS device.

14. The device of claim 13, wherein the MEMS device comprises an interferometric modulator.

15. The device of claim 13, wherein the circuitry is further configured to determine whether the driving voltage is substantially the same as a transition voltage of the MEMS device based upon the frequency components of the measured current.

16. The device of claim 13, wherein the circuitry is further configured to identify frequency components of the measured current by performing a Fourier transform on the measured current.

17. A device, comprising:

means for applying a sinusoidal voltage to a microelectromechanical system (MEMS) device;

means for measuring a current through the MEMS device;

means for identifying frequency components of the measured current; and

means for determining whether the frequency components of the measured current are indicative of non-linear behavior of the MEMS device.

18. The device of claim 17, wherein the means for identifying the frequency components of the measured circuit comprise circuitry for performing a Fourier transform on the measured circuit.

19. The device of claim 17, additionally comprising circuitry configured to determine whether the applied voltage is substantially the same as a transition voltage based upon the frequency components of the measured current.