Measurement and apparatus for electrical measurement of electrical drive parameters for a MEMS based display

• US 8,775,107 B2
• Filed: 06/18/2012
• Issued: 07/08/2014
• Est. Priority Date: 02/11/2008
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Govil, Alok, Djordjev, Kostadin, Lewis, Alan, Van Lier, Wilhelmus Johannes Robertus
• Primary Examiner(s): Le, John H
• Application Number:
  US13/526,192
• Publication Number:
  US 20120249122A1
• Time in Patent Office: 750 Days
• Field of Search: 702/64, 702/65, 702/104, 702/117, 702/127, 702/189, 735/141.6, 735/143.8, 735/80, 324/73.1, 324/117.R, 324/658, 324/671, 341/152, 345/54, 345/212, 359/254, 359/290, 359/291, 359/298, 359/318, 361/207, 438/52
• US Class Current: 702/64
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81C 99/0045 End test of the packaged device
• CPC Class Codes: G01R 19/0046 characterised by a specific application or detail not covered by any other subgroup of G01R19/00
• 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 2310/061 for resetting or blanking
• 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 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833
• CPC Class Codes: G09G 5/003 Details of a display terminal, the details relating to the control arrangement of the display terminal and to the interfaces thereto specific for a CRT G09G1/165; for a flat panel G09G3/2092

Abstract

Methods and devices to measure voltage margins of electromechanical devices are disclosed. The voltage margins are determined based on responses to test voltages which cause the devices to change states. State changes of the devices are detected by monitoring integrated current or charge used to drive the devices with the test voltages.

Claims

1. A method of measuring a threshold voltage for an electromechanical device, the method comprising:

applying a plurality of signals to the device and sensing an electrical characteristic of each of the signals;

determining, based on the sensed electrical characteristic, whether each of the signals changes a state of the device;

determining the threshold voltage based on, at least in part, a signal resulting in the state change.

2. The method of claim 1, wherein the signals are applied to the device in response to the device being turned on.

3. The method of claim 1, wherein determining the threshold voltage comprises determining a voltage sufficient to cause a movable element of the device to move.

4. The method of claim 1, wherein sensing the electrical characteristic comprises at least one of integrating a current used to apply the signals, integrating charge used to apply the signals, measuring current used to apply the signals, and measuring charge used to apply the signals.

5. The method of claim 1, wherein the device comprises a plurality of elements, the method further comprising:

applying a plurality of signals to each of the elements and sensing an electrical characteristic of each of the signals;

determining, based on the sensed electrical characteristic, whether each of the signals changes the state of a determined number of elements; and

determining the threshold voltage based on, at least in part, a signal resulting in the state change of the determined number of elements.

6. The method of claim 1, further comprising:

sensing the electrical characteristic while applying one or more positive voltage transitions to the device;

applying a test voltage to the device;

sensing the electrical characteristic while applying one or more negative voltage transitions to the device; and

determining whether the test voltage changed the state of the device based on the difference between the electrical characteristic sensed for positive voltage transitions and the electrical characteristic sensed for negative voltage transitions.

7. The method of claim 1, wherein the device comprises an array of elements and the signals comprise positive voltage transitions and negative voltage transitions, the method further comprising:

applying positive voltage transitions to a first portion of the array; and

applying negative voltage transitions to a second portion of the array; and

determining whether the state of a number of elements changed based on the difference between the electrical characteristic sensed for positive voltage transitions and the electrical characteristic sensed for negative voltage transitions.

8. The method of claim 1, further comprising determining an actuation threshold voltage based on, at least in part, a particular signal resulting in the device changing from a released state to an actuated state, the particular signal having a starting voltage and an ending voltage, the starting and ending voltages having opposite polarities.

9. The method of claim 1, further comprising determining a release threshold voltage based on, at least in part, a particular signal resulting in the device changing from an actuated state to a released state, the particular signal having a starting voltage and an ending voltage, the starting and ending voltages having opposite polarities.

10. The method of claim 1, the device comprising a plurality of elements, the method further comprising determining a release threshold voltage of a first element based on, at least in part, a particular signal applied to a second element resulting in the first element changing from a released to an actuated state.

11. The method of claim 1, the device comprising a plurality of elements, the method further comprising determining an actuation threshold voltage of a first element based on, at least in part, a particular signal applied to a second element resulting in the first element changing from an actuated state to a released state.

12. The method of claim 1, wherein the device comprises an array of elements and the signals comprise positive voltage transitions and negative voltage transitions, the method further comprising:

applying a positive voltage transition to a first portion of the array; and

applying a negative voltage transition to a second portion of the array,

wherein sensing the electrical characteristic comprises sensing a difference between the electrical characteristic resulting from the positive voltage transition and the electrical characteristic resulting from the negative voltage transition.

13. An electromechanical device, comprising:

a pair of electrodes;

a driver configured to apply a plurality of signals to the electrodes;

a sensor configured to sense an electrical characteristic of each of the signals;

a comparison circuit configured to determine, based on the sensed electrical characteristic, whether each of the signals changes a state of the device; and

a processor configured to determine a threshold voltage based on, at least in part, a signal resulting in a state change.

14. The device of claim 13, wherein the driver is configured to apply the signals to the device in response to the device being turned on.

15. The device of claim 13, wherein the sensor is further configured to integrate a current applied to the device.

16. The device of claim 13, wherein the sensor is further configured to measure current applied to the device.

17. The device of claim 13, wherein to sense the electrical characteristic, the sensor is configured to at least one of integrate a current used to apply the signals, integrate charge used to apply the signals, measure current used to apply the signals, and measure charge used to apply the signals.

18. The device of claim 13, further comprising a plurality of elements, wherein:

the driver is further configured to apply a plurality of voltage transitions to each of the elements;

the sensor is further configured to sense the electrical characteristic during one or more transitions;

the processor is further configured to determine, based on the sensed electrical characteristic, whether each of the one or more transitions changes the state of a determined number of elements and to determine a second threshold based on the electrical characteristic sensed during a transition resulting in a state change of the determined number of elements.

19. The device of claim 13, wherein:

the driver is further configured to apply one or more positive voltage transitions to the electrodes, apply a test voltage to the electrodes, and apply one or more negative voltage transitions to the electrodes;

the sensor is configured to sense the electrical characteristic at least during the applications of the one or more positive voltage transitions and the one or more negative voltage transitions to the electrodes; and

the processor is further configured to determine whether the test voltage changed the state of the device based on the difference between the electrical characteristic sensed for positive voltage transitions and the electrical characteristic sensed for negative voltage transitions.

20. The device of claim 13, further comprising an array of elements and the signals comprise positive voltage transitions and negative voltage transitions, wherein the driver is further configured to apply one or more positive voltage transitions to a first portion of the array and to apply one or more negative voltage transitions to a second portion of the array, and the comparison circuit is configured to determine whether the state of a number of elements changed based on the difference between the electrical characteristic sensed for positive voltage transitions and the electrical characteristic sensed for negative voltage transitions.

21. The device of claim 13, the processor further configured to determine an actuation threshold voltage based on, at least in part, a particular signal resulting in the device changing from a released state to an actuated state, the particular signal having a starting voltage and an ending voltage, the starting and ending voltages having opposite polarities.

22. The device of claim 13, wherein the processor is configured to determine a release threshold voltage based on, at least in part, a particular signal resulting in the device changing from an actuated state to a released state, the particular signal having a starting voltage and an ending voltage, the starting and ending voltages having opposite polarities.

23. The device of claim 13, further comprising a plurality of elements, wherein the processor is configured to determine a release threshold voltage of a first element based on, at least in part, a particular signal applied to a second element resulting in the first element changing from a released to an actuated state.

24. The device of claim 13, further comprising a plurality of elements, the processor configured to determine an actuation threshold voltage of a first element based on, at least in part, a particular signal applied to a second element resulting in the first element changing from an actuated state to a released state.

25. The device of claim 13, further comprising determining one or more driving voltages based on the measured threshold voltage.

26. An electromechanical device configured to be driven to an actuated state as a result of being driven with an actuation voltage, to be driven to a released state as a result of being driven with a release voltage, and to maintain a current state as a result of being driven with a hold voltage, the device comprising:

first and second means for actuating and releasing according to a voltage;

means for applying a plurality of signals to the first and second actuating and releasing means;

means for sensing an electrical characteristic of each of the signals;

means for determining, based on the sensed electrical characteristic, whether each of the one or more signals changes a state of the device; and

means for determining the threshold voltage based on, at least in part, a signal resulting in the state change.

27. The device of claim 26, wherein the applying means comprises a driver, the indicating means comprises a sensor, the state change determining means comprises a comparison circuit, and the threshold voltage determining means comprises a processor.

28. The device of claim 26, wherein the applying means is configured to apply the signals to the device in response to the device being turned on.

29. The device of claim 26, further comprising means for determining one or more driving voltages based on the threshold voltage.

30. The device of claim 26, wherein the sensing means is configured to at least one of integrate a current used to apply the signals, integrate charge used to apply the signals, measure current used to apply the signals, and measure charge used to apply the signals.