Method and system for writing data to MEMS display elements

• US 20070182707A1
• Filed: 02/09/2006
• Published: 08/09/2007
• Est. Priority Date: 02/09/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Kothari, Manish
• Granted Patent: US 8,194,056 B2
• Time in Patent Office: Days
• US Class Current: 345/108
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 3/3466 based on interferometric effect
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Another embodiment has a method of driving a display device including an array of MEMS elements is disclosed. The MEMS elements are characterized by a preferred set of drive potential differences including preferred positive and preferred negative actuation potential differences, preferred positive and preferred negative hold potential differences, and a preferred release potential difference, where the preferred set of drive potential differences is symmetric about a voltage differing from 0V by an offset δV. Another embodiment has a reduced set of supply voltages are used, while maintaining the charge balancing effects of applying potential differences of opposite polarity without visible artifacts.

Claims

1. A display device comprising a set of MEMS display elements configured as an array of rows and columns of MEMS elements, wherein the MEMS elements are characterized by a preferred set of drive potential differences comprising preferred positive and preferred negative actuation potential differences, preferred positive and preferred negative hold potential differences, and a preferred release potential difference, wherein the preferred set of drive potential differences is symmetric about a voltage differing from 0V by an offset δ

V and wherein drive potential differences are applied to each MEMS element as a difference between a column voltage and a row voltage, said method comprising;

generating a set of four different voltage levels;

writing display data to the array by applying voltages to each column of the array and each row of the array so as to apply first and second actuation potential differences, first and second hold potential differences, and first and second release potential differences, wherein said voltages are selected only from said set of four different voltage levels, and wherein first and second hold potentials are of opposite polarity.

2. The method of claim 1, wherein said first hold potential is a positive polarity such that the column is at a higher potential than the row, and wherein said second hold potential is a negative polarity such that the row is at a higher potential than the column.

3. The method of claim 1, wherein δ

V is a positive value.

4. The method of claim 1, wherein δ

V is a negative value.

5. The method of claim 1, wherein voltages applied to the columns are selected from a set of two voltages, wherein voltages applied to the rows are selected from a set of three voltages, and wherein the set of three voltages and the set of two voltage share one common voltage.

6. The method of claim 5, wherein one of the set of three voltages is shifted from one of the set of two voltages by about 2δ

V.

7. The method of claim 5, wherein the common voltage is about 0 V.

8. The method of claim 5, wherein the common voltage is about 5 V or more.

9. The method of claim 1, wherein the first and second actuation potential differences are symmetric about the offset voltage δ

V.

10. The method of claim 1, wherein the first and second release potential differences are symmetric about the offset voltage δ

V.

11. The method of claim 1, wherein the first and second hold potential differences are symmetric about the offset voltage δ

V.

12. A microelectromechanical system (MEMS) display device comprising:

an array of rows and columns of MEMS elements, wherein the MEMS elements are characterized by a preferred set of drive potential differences comprising preferred positive and preferred negative actuation potential differences, preferred positive and preferred negative hold potential differences, and a preferred release potential difference, wherein the preferred set of drive potential differences is symmetric about a voltage differing from 0V by an offset δ

V; and

an array driver configured to write display data to the array by applying voltages to each column of the array and each row of the array so as to apply first and second actuation potential differences, first and second hold potential differences, and first and second release potential differences, wherein the voltages are selected from a set of only four different voltage levels, and wherein first and second hold potentials are of opposite polarity.

13. The method of claim 12, wherein said first hold potential is a positive polarity such that the column is at a higher potential than the row, and wherein said second hold potential is a negative polarity such that the row is at a higher potential than the column.

14. The method of claim 12, wherein δ

V is a positive value.

15. The method of claim 12, wherein δ

V is a negative value.

16. The device of claim 12, wherein the array controller is configured to apply voltages to the columns selected from a set of two voltages, and to apply voltages to the rows selected from a set of three voltages, and wherein the set of three voltages and the set of two voltages share one common voltage.

17. The device of claim 16, wherein one of the set of three voltages is shifted from one of the set of two voltages by about 2δ

V.

18. The device of claim 16, wherein the common voltage is about 0 V.

19. The device of claim 16, wherein the common voltage is about 5 V or more.

20. The device of claim 12, wherein the first and second actuation potential differences are symmetric about the offset voltage δ

V.

21. The device of claim 12, wherein the first and second release potential differences are symmetric about the offset voltage δ

V.

22. The device of claim 12, wherein the first and second hold potential differences are symmetric about the offset voltage δ

V.

23. The apparatus of claim 12, further comprising:

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.

24. The apparatus of claim 23, further comprising a controller configured to send at least a portion of the image data to the driver circuit.

25. The apparatus of claim 23, further comprising an image source module configured to send said image data to said processor.

26. The apparatus of claim 25, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

27. The apparatus of claim 23, further comprising an input device configured to receive input data and to communicate said input data to said processor.

28. A method of driving a display device comprising a set of MEMS display elements configured as an array of rows and columns of MEMS elements, wherein said MEMS elements are characterized by a preferred set of drive potential differences comprising preferred positive and preferred negative actuation potential differences, preferred positive and preferred negative hold potential differences, and a preferred release potential difference, wherein the preferred set of drive potential differences is symmetric about a voltage differing from 0V by an offset δ

V and wherein drive potential differences are applied to each MEMS element as a difference between a column voltage and a row voltage, the method comprising;

generating a set of four different voltage levels;

writing display data to the array by applying voltages to each column of the array and each row of the array so as to apply first and second actuation potential differences, first and second hold potential differences, and first and second release potential differences, wherein the voltages are selected only from the set of four different voltage levels, and wherein at least one of first and second actuation potentials, first and second hold potentials, and first and second release potentials are of opposite polarity and are symmetric about the offset voltage δ

V.

29. The method of claim 28, wherein said first hold potential is a positive polarity such that the column is at a higher potential than the row, and wherein said second hold potential is a negative polarity such that the row is at a higher potential than the column.

30. The method of claim 28, wherein δ

V is a positive value.

31. The method of claim 28, wherein δ

V is a negative value.

32. The method of claim 28, wherein voltages applied to the columns are selected from a set of two voltages, wherein voltages applied to the rows are selected from a set of three voltages, and wherein the set of three voltages and the set of two voltage share one common voltage.

33. The method of claim 32, wherein each of the first and second actuation potentials, the first and second hold potentials, and the first and second hold potentials are of opposite polarity and are symmetric about the offset voltage δ

V.

34. The method of claim 28, wherein the light modulation characteristics of each MEMS display element when driven with a positive polarity potential is substantially identical to the light modulation characteristics when driven with a negative polarity potential.

35. A microelectromechanical system (MEMS) display device comprising:

means for displaying rows and columns of image data, wherein said means are characterized by a preferred set of drive potential differences comprising preferred positive and preferred negative actuation potential differences, preferred positive and preferred negative hold potential differences, and a preferred release potential difference, wherein the preferred set of drive potential differences is symmetric about a voltage differing from 0V by an offset δ

V; and

means for writing image data to the means for displaying by applying voltages to each column of the array and each row of the array so as to apply first and second actuation potential differences, first and second hold potential differences, and first and second release potential differences, wherein the voltages are selected from a set of only four different voltage levels, and wherein first and second hold potentials are of opposite polarity.

36. The device of claim 35, wherein said means for displaying comprises an array of MEMS elements configured as interferometric modulators.

37. The device of claim 36, wherein said means for writing image data comprises an array driver circuit.