System and method of driving a MEMS display device

• US 20060250335A1
• Filed: 04/28/2006
• Published: 11/09/2006
• Est. Priority Date: 05/05/2005
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Chui, Clarence, Hastings, Robert S., Stewart, Richard A.
• Granted Patent: US 7,920,136 B2
• Time in Patent Office: Days
• US Class Current: 345/84
• CPC Class Codes: G09G 2310/0205 Simultaneous scanning of several lines in flat panels
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• 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 3/3466 based on interferometric effect

Abstract

Methods of writing display data to MEMS display elements are configured to minimize charge buildup and differential aging. Simultaneous to writing rows of image data, a pre-write operation is performed on a next row. The pre-write operation writes either image data or the inverse of the image data to the next row. In some embodiments, the selection between writing image data and writing inverse image data is performed in a random or pseudo-random manner.

Claims

1. A method of writing data to a micro-electromechanical system (MEMS) device having first and second input electrodes, wherein the MEMS device is configured to be in an actuated state when a voltage difference between the first and second electrodes is above a threshold, wherein the voltage difference has one of first and second polarities, the method comprising:

randomly or pseudo-randomly selecting between the first and second polarities; and

applying the voltage difference across the first and second electrodes, the applied voltage difference being above the threshold and having the selected polarity.

2. The method of claim 1, further comprising repeatedly applying voltage differences across the first and second electrodes, wherein each of the repeatedly applied voltage differences has a randomly or pseudo-randomly selected polarity.

3. The method of claim 2, wherein the polarity is repeatedly selected such that after a number of selections, the number of first polarity selections exactly equals the number of second polarity selections.

4. The method of claim 2, wherein the polarity is repeatedly selected such that after a number of selections, the number of first polarity selections is different from the number of second polarity selections by a predetermined amount.

5. The method of claim 2, wherein the polarity is repeatedly selected such that the maximum number of consecutive occurrences of the first polarity is the same as the maximum number of consecutive occurrences of the second polarity.

6. A method of writing data to an array of micro-electromechanical system (MEMS) devices, wherein each device has first and second input electrodes and is configured to be in a first state when the voltage difference between the first and second electrodes is below a first threshold, and to be in a second state when the voltage difference between the first and second electrodes is above a second threshold, wherein the voltage difference has one of first and second polarities, the method comprising:

randomly or pseudo-randomly selecting a first row strobe value corresponding to one of the first and second polarities of the voltage difference between the first and second electrodes of the MEMS devices; and

applying the strobe value to a first row of the array.

7. The method of claim 6, further comprising repeatedly applying row strobe values to the first row, wherein each of the repeatedly applied row strobe values has a randomly or pseudo-randomly selected polarity.

8. The method of claim 7, wherein the polarity is repeatedly selected such that after a number of selections, the number of first polarity selections exactly equals the number of second polarity selections.

9. The method of claim 7, wherein the polarity is repeatedly selected such that the maximum number of consecutive occurrences of the first polarity is the same as the maximum number of consecutive occurrences of the second polarity.

10. The method of claim 6, further comprising applying the first row strobe value to a plurality of rows of the array.

11. The method of claim 10, wherein the plurality of rows comprises substantially all of the rows of the array.

12. The method of claim 6, further comprising:

randomly or pseudo-randomly selecting a second row strobe value corresponding to one of the first and second polarities; and

applying the second row strobe value to a second row of the array.

13. The method of claim 12, wherein applying the first and second row strobe values occur within the same frame period.

14. The method of claim 12, wherein applying the first and second row strobe values occur substantially simultaneously.

15. The method of claim 12, wherein the first and second rows are adjacent.

16. A method of writing data to an array of micro-electromechanical system (MEMS) devices, wherein each device has first and second input electrodes and is configured to be in a first state when the voltage difference between the first and second electrodes is below a first threshold, and to be in a second state when the voltage difference between the first and second electrodes is above a second threshold, wherein the voltage difference has one of first and second polarities, the method comprising:

applying image data to one or more columns of the array; and

substantially simultaneously applying a first row strobe to a first row of the array and applying a second row strobe to a second row of the array.

17. The method of claim 16, wherein the value of the first row strobe is randomly or pseudo-randomly selected from values corresponding to the first and second polarities.

18. The method of claim 16, wherein the value of the first row strobe is repeatedly selected such that after a number of selections, the number of first row strobe value selections corresponding to the first polarity exactly equals the number of first row strobe value selections corresponding to the second polarity.

19. The method of claim 16, wherein the polarity is repeatedly selected such that the maximum number of consecutive occurrences of first row strobe value selections corresponding to the first polarity is the same as the maximum number of consecutive occurrences of first row strobe value selections corresponding to the second polarity.

20. The method of claim 16, wherein the value of the second row strobe is randomly or pseudo-randomly selected from values corresponding to first and second polarities.

21. The method of claim 16, wherein the first and second rows are adjacent.

22. The method of claim 16, wherein said first and second rows are not adjacent

23. A method of writing data to an array of micro-electromechanical system (MEMS) devices, the method comprising:

writing image data to a first portion of the array; and

writing either the same image data or the inverse of the image data to a second portion of the array,

wherein writing to the first portion and writing to the second potion occur substantially simultaneously.

24. The method of claim 23, wherein said portions are different rows of the array.

25. The method of claim 24, wherein the first and second rows are adjacent.

26. The method of claim 24, wherein writing to the first and second rows comprises applying a row strobe to the first and second rows.

27. The method of claim 23, further comprising randomly or pseudo-randomly selecting between writing the same image data and writing the of the inverse image data.

28. The method of claim 23, further comprising:

writing second image data to the second portion of the array; and

writing either the same second image data or the inverse of the same second image data to a third portion of the array.

29. A micro-electromechanical system (MEMS) device, comprising:

an array of MEMS elements, wherein each element has first and second input electrodes and is configured to be in a first state when the voltage difference between the first and second electrodes is below a first threshold, and to be in a second state when the voltage difference between the first and second electrodes is above a second threshold, wherein the voltage difference has one of first and second polarities;

a PN generator circuit configured to randomly or pseudo-randomly select between the first and second polarities; and

a driver circuit configured to apply a first row strobe value to a first row of the array, the first row strobe value corresponding to the polarity selected by the PN generator.

30. The device of claim 29, wherein the driver circuit is configured to repeatedly apply row strobe values to the first row, wherein each of the repeatedly applied row strobe values corresponds to a polarity selected by the PN generator.

31. The device of claim 29, wherein the PN generator is configured to repeatedly select between the first and second polarities such that after a number of selections, the number of first polarity selections exactly equals the number of second polarity selections.

32. The device of claim 29, wherein the PN generator is configured to repeatedly select between the first and second polarities such that the maximum number of consecutive occurrences of the first polarity is the same as the maximum number of consecutive occurrences of the second polarity.

33. The device of claim 29, wherein the driver circuit is further configured to apply the first row strobe value to a plurality of rows of the array.

34. The device of claim 33, wherein the plurality of rows comprises substantially all of the rows of the array.

35. The device of claim 29, wherein the driver circuit is further configured to apply a second row strobe value to a second row of the array, wherein the second row strobe value corresponds to a second polarity selected by the PN generator, and the driver circuit is configured to apply the first and second row strobe values substantially simultaneously.

36. The device of claim 35, wherein the first and second rows are adjacent.

37. The device of claim 29, wherein the PN generator circuit comprises:

an unbalanced PN generator configured to generate an unbalanced output; and

a balancer, configured to receive the unbalanced output and selectively output either the unbalanced output, or an inverted unbalanced output, wherein the balancer is configured to output any of a plurality of signal values, and the probability that the balancer outputs any one of the signal values is substantially equal to the probability that the balancer outputs any other of the signal values.

38. The device of claim 37, wherein the unbalanced PN generator comprises a shift register, and the unbalanced PN generator is configured to periodically produce a pseudo-random sequence using the shift register.

39. The device of claim 37, wherein the balancer comprises an XOR circuit with first and second inputs.

40. The device of claim 39, wherein the unbalanced output is provided to the first input of the XOR circuit and a periodic signal is provided to the second input of the XOR circuit, and the unbalanced PN generator comprises a shift register, the shift register being configured to produce a periodic pseudo-random sequence, wherein the period of the pseudo-random sequence is substantially one half the period of the periodic signal provided to the second input of the XOR circuit.

41. An apparatus including the device of claim 29, further comprising:

a display;

a processor that is configured to communicate with said display, said processor being configured to process image data; and

a memory device that is configured to communicate with said processor.

42. The apparatus as recited in claim 41, wherein the driver circuit further configured to send at least one signal to said display.

43. The apparatus as recited in claim 42, further comprising a controller configured to send at least a portion of said image data to said driver circuit.

44. The apparatus as recited in claim 41, further comprising an image source module configured to send said image data to said processor.

45. The apparatus as recited in claim 44, wherein said image source module comprises at least one of a receiver, transceiver, and transmitter.

46. The apparatus as recited in claim 41, further comprising an input device configured to receive input data and to communicate said input data to said processor.

47. The apparatus of claim 41, the display being bi-stable.