Digital micromirror device and method of driving digital micromirror device

• US 6,781,742 B2
• Filed: 07/11/2001
• Issued: 08/24/2004
• Est. Priority Date: 07/11/2000
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun, Yamazaki, Shunpei
• Primary Examiner(s): Schwartz, Jordan M.
• Assistant Examiner(s): STULTZ, JESSICA T
• Application Number:
  US09/903,783
• Publication Number:
  US 20020051096A1
• Time in Patent Office: 1,140 Days
• Field of Search: 359/290, 359/291, 359/295, 359/296, 348/750, 348/756, 348/770, 348/771, 348/775
• US Class Current: 359/290
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0857 Static memory circuit, e.g. flip-flop
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 2310/0267 Details of drivers for scan electrodes, other than drivers for liquid crystal, plasma or OLED displays
• CPC Class Codes: G09G 2310/0275 Details of drivers for data electrodes, other than drivers for liquid crystal, plasma or OLED displays, not related to handling digital grey scale data or to communication of data to the pixels by means of a current
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2340/0428 Gradation resolution change
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833

Abstract

A spatial light modulation device capable of displaying a large number of gray scales is provided. The inventors of the present invention proposed a spatial light modulation device having: a first structure in which a switching transistor and an erasure transistor, each having its gate electrode connected to a different scanning line, are formed in each pixel, and whose switching is controlled separately; or a second structure in which two switching transistors, each having its gate electrode connected to a different scanning line, are formed in each pixel, and whose switching is controlled separately.

Claims

1. A digital micromirror device comprising:

a first electrode and a second electrode;

a micromirror located over said first electrode and said second electrode;

a first switching element;

a second switching element; and

a SRAM electrically connected to the first and second switching elements and including transistors distinct from the first and second switching elements,

wherein;

an output of said first switching element is connected to said first electrode;

an output of said second switching element is connected to said second electrode;

an input of said SRAM is connected to said first electrode;

an output of said SRAM is connected to said second electrode; and

the voltages of the input and the output of said SRAM mutually differ.

40. A digital micromirror device according to claim 1, wherein said first switching element is a first transistor and said second switching element is a second transistor.

45. A digital micromirror device according to claim 40, wherein a first gate electrode of said first transistor is electrically connected to a first signal line and said second gate electrode of said second transistor is electrically connected to a second signal line.

2. A digital micromirror device comprising:

a micromirror;

a first electrode and a second electrode for changing the inclination of the micromirror;

a first switching element;

a second switching element; and

a SRAM electrically connected to the first and second switching elements and including transistors distinct from the first and second switching elements,

wherein;

an output of said first switching element is connected to said first electrode;

an output of said second switching element is connected to said second electrode;

an input of said SRAM is connected to said first electrode;

an output of said SRAM is connected to said second electrode; and

voltages of the input and the output of said SRAM mutually differ.

6. The digital micromirror device according to claim 2, wherein the SRAM comprises two p-channel transistors and two n-channel transistors.

10. The digital micromirror device according to claim 2, wherein the SRAM comprises two p-channel transistors and two resistors.

14. The digital micromirror device according to claim 2, wherein the SRAM comprises two n-channel transistors and two resistors.

18. An electronic device having the digital micromirror device according to claim 2.

22. An electronic device having the digital micromirror device according to claim 6.

25. The electronic device according to claim 18, wherein the electronic device is selected from the group consisting of a projector, a printer, and a copy machine.

29. The electronic device according to claim 22, wherein the electronic device is selected from the group consisting of a projector, a printer, and a copy machine.

41. A digital micromirror device according to claim 2, wherein said first switching element is a first transistor and said second switching element is a second transistor.

46. A digital micromirror device according to claim 41, wherein a first gate electrode of said first transistor is electrically connected to a first signal line and said second gate electrode of said second transistor is electrically connected to a second signal line.

3. A digital micromirror device comprising:

a micromirror;

a first electrode and a second electrode for changing the inclination of said micromirror;

a first switching element;

a second switching element; and

a SRAM electrically connected to the first and second switching elements and including transistors distinct from the first and second switching elements,

wherein;

a second voltage is imparted to said second electrode by said SRAM when a first voltage is imparted to said first electrode by said first switching element;

said first voltage is imparted to said second electrode by said SRAM when said second voltage is imparted to said first electrode by said first switching element;

said first voltage is imparted to said first electrode by said SRAM when said second voltage is imparted to said second electrode by said second switching element;

a switching of said first switching element is controlled by a first signal; and

a switching of said second switching element is controlled by a second signal.

7. The digital micromirror device according to claim 3, wherein the SRAM comprises two p-channel transistors and two n-channel transistors.

11. The digital micromirror device according to claim 3, wherein the SRAM comprises two p-channel transistors and two resistors.

15. The digital micromirror device according to claim 3, wherein the SRAM comprises two n-channel transistors and two resistors.

19. An electronic device having the digital micromirror device according to claim 3.

23. An electronic device having the digital micromirror device according to claim 7.

26. The electronic device according to claim 19, wherein the electronic device is selected from the group consisting of a projector, a printer, and a copy machine.

30. The electronic device according to claim 23, wherein the electronic device is selected from the group consisting of a projector, a printer, and a copy machine.

42. A digital micromirror device according to claim 3, wherein said first switching element is a first transistor and said second switching element is a second transistor.

47. A digital micromirror device according to claim 42, wherein a first gate electrode of said first transistor is electrically connected to a first signal line and said second gate electrode of said second transistor is electrically connected to a second signal line.

4. A digital micromirror device comprising:

a micromirror;

a first electrode and a second electrode for changing the inclination of said micromirror;

a first switching element for imparting a first voltage or a second voltage to said first electrode;

a second switching element for imparting said first voltage or said second voltage to said second electrode; and

a SRAM electrically connected to the first and second switching elements and including transistors distinct from the first and second switching elements,

wherein the SRAM imparts said second voltage to one of said first electrode and said second electrode, when said first voltage is imparted to the other one of electrodes, and the SRAM imparts said first voltage to one of said first electrode and said second electrode, when said second voltage is imparted to the other one of said electrodes.

8. The digital micromirror device according to claim 4, wherein the SRAM comprises two p-channel transistors and two n-channel transistors.

12. The digital micromirror device according to claim 4, wherein the SRAM comprises two p-channel transistors and two resistors.

16. The digital micromirror device according to claim 4, wherein the SRAM comprises two n-channel transistors and two resistors.

20. An electronic device having the digital micromirror device according to claim 4.

24. An electronic device having the digital micromirror device according to claim 8.

27. The electronic device according to claim 20, wherein the electronic device is selected from the group consisting of a projector, a printer, and a copy machine.

31. The electronic device according to claim 24, wherein the electronic device is selected from the group consisting of a projector, a printer, and a copy machine.

43. A digital micromirror device according to claim 4, wherein said first switching element is a first transistor and said second switching element is a second transistor.

48. A digital micromirror device according to claim 43, wherein a first gate electrode of said first transistor is electrically connected to a first signal line and said second gate electrode of said second transistor is electrically connected to a second signal line.

5. A digital micromirror device comprising:

a micromirror;

a first electrode and a second electrode for changing the inclination of said micromirror;

a first switching element for imparting a first voltage or a second voltage to said first electrode;

a second switching element for imparting said first voltage or said second voltage to said second electrode; and

a SRAM electrically connected to the first and second switching elements and including transistors distinct from the first and second switching elements,

wherein the SRAM imparts said second voltage to one of said first electrode and said second electrode, when said first voltage is imparted to the other one of electrodes, and the SRAM imparts said first voltage to one of said first electrode and said second electrode, when said second voltage is imparted to the other one of the electrodes;

wherein;

a switching of said first switching element is controlled by a first signal, and

a switching of said second switching element is controlled by a second signal.

9. The digital micromirror device according to claim 5, wherein the SRAM comprises two p-channel transistors and two n-channel transistors.

13. The digital micromirror device according to claim 5, wherein the SRAM comprises two p-channel transistors and two resistors.

17. The digital micromirror device according to claim 5, wherein the SRAM comprises two n-channel transistors and two resistors.

21. An electronic device having the digital micromirror device according to claim 5.

28. The electronic device according to claim 21, wherein the electronic device is selected from the group consisting of a projector, a printer, and a copy machine.

44. A digital micromirror device according to claim 5, wherein said first switching element is a first transistor and said second switching element is a second transistor.

49. A digital micromirror device according to claim 44, wherein a first gate electrode of said first transistor is electrically connected to a first signal line and said second gate electrode of said second transistor is electrically connected to a second signal line.

32. A method of driving a digital micromirror device having a plurality of pixels, each pixel including:

a micromirror;

a first electrode and a second electrode for changing the inclination of said micromirror; and

a SRAM;

said method comprising the steps of;

preparing n display periods and j non-display periods within one frame period in each of said plurality of pixels;

imparting a second voltage to said second electrode by said SRAM in each of n display periods if a first voltage of a digital signal of bits corresponding to each of n display periods is imparted to said first electrode of each of said plurality of pixels;

imparting said first voltage to said second electrode by said SRAM in each of n display periods if said second voltage of the digital signal of bits corresponding to each of n display periods is imparted to said first electrode of each of said plurality of pixels;

imparting said first voltage to said first electrode by said SRAM in each of j non-display periods if said second voltage is imparted to said second electrode of each of said plurality ofpixels;

preparing any one of said n display periods again, after all of said n display periods appear;

wherein a ratio of the lengths of said n display periods is expressed as 2⁰;

2¹;

. . . ;

2<sup>(n−

1)</sup>.

36. The method of driving a digital micromirror device according to claim 32, wherein black is displayed when a second voltage is imparted to a second electrode in each of a plurality of pixels.

33. A method of driving a digital micromirror device having a plurality of pixels, each pixel including:

a micromirror;

a first electrode and a second electrode for changing the inclination of said micromirror;

a SRAM;

a first switching element; and

a second switching element;

said method comprising the steps of;

preparing n display periods and j non-display periods within one frame period in each of said plurality of pixels;

imparting a second voltage to said second electrode by said SRAM in each of n display periods if a first voltage of a digital signal of bits corresponding of each of n display periods is imparted to said first electrode of each of said plurality of pixels, in accordance with said first switching element turning on;

imparting said first voltage to said second electrode by said SRAM in each of n display periods if said second voltage of the digital signal of bits corresponding to each of n display periods is imparted to said first electrode of each of said plurality of pixels, in accordance with said first switching element turning on;

imparting said first voltage to said first electrode by said SRAM in each of j non-display periods if said second voltage is imparted to said second electrode of each of said plurality of pixels, in accordance with said second switching element turning on;

preparing any one of said n display periods again, after all of said n display periods appear;

wherein a ratio of the lengths of said n display periods is expressed as 2⁰;

2¹;

. . . ;

2<sup>(n−

1)</sup>.

37. The method of driving a digital micromirror device according to claim 33, wherein black is displayed when a second voltage is imparted to a second electrode in each of a plurality of pixels.

34. A method of driving a digital micromirror device having a plurality of pixels, each pixel including:

a micromirror;

a first electrode and a second electrode for changing the inclination of said micromirror; and

a SRAM for imparting a second voltage to one of said first electrode and said second electrode, when a first voltage is imparted to the other one of electrodes, and imparting said first voltage to one of said first electrode and said second electrode, when said second voltage isimparted to the other one of the electrodes;

said method comprising the steps of;

preparing n first display periods and j second display periods within one frame period in each of said plurality of pixels;

imparting said first voltage or said second voltage of a digital signal of bits corresponding to each of n first display periods to said first electrode of each of said plurality of pixels in each of n first display periods;

imparting said first voltage or said second voltage of a digital signal of bits corresponding to each of j second display periods to said second electrode of each of said plurality of pixels in each of j second display periods;

preparing one of said n first display periods and one of said j second display periods again, after all of said n first display periods and j second display periods appear;

wherein a ratio of the lengths of said n first display periods and the lengths of said j second display periods is expressed as 2⁰;

2¹;

. . . ;

2<sup>(n−

1)</sup>.

38. The method of driving a digital micromirror device according to claim 34, wherein black is displayed when a second voltage is imparted to a second electrode in each of a plurality of pixels.

35. A method of driving a digital micromirror device having a plurality of pixels, each pixel including:

a micromirror;

a first electrode and a second electrode for changing the inclination of the micromirror;

a first switching element;

a second switching element; and

a SRAM for imparting a second voltage to one of said first electrode and said second electrode, when said first voltage is imparted to the other one of electrodes, imparting said first voltage to one of said first electrode and said second electrode, when said second voltage is imparted to the other one of the electrodes;

said method comprising the steps of;

preparing n first display periods and j second display periods within one frame period in each of said plurality of pixels;

imparting said first voltage or said second voltage of a digital signal of bits corresponding to each of n first display periods to said first electrode of each of said plurality of pixels in each of n first display periods, in accordance with said first switching element turning on;

imparting said first voltage or said second voltage of a digital signal of bits corresponding to each of j second display periods to said second electrode of each of said plurality of pixels in each of j second display periods, in accordance with said second switching element turning on;

preparing any one of said n first display periods and any one of said j second display periods again, after all of said n first display periods and j second display periods appear; and

wherein a ratio of the lengths of said n first display periods and the lengths of said j second display periods is expressed as 2⁰;

2¹;

. . . ;

2<sup>(n−

1)</sup>.

39. The method of driving a digital micromirror device according to claim 35, wherein black is displayed when a second voltage is imparted to a second electrode in each of a plurality of pixels.