Optical waveguide display with movable actuators which cause light leakage in waveguide at each display elements to provide gradation in a display image by temporal subfield modulation

• US 6,323,833 B1
• Filed: 03/23/1998
• Issued: 11/27/2001
• Est. Priority Date: 03/24/1997
• Status: Expired due to Fees

• Current Assignee: NGK Insulators Limited
• Original Assignee: NGK Insulators Limited
• Inventors: Takeuchi, Yukihisa, Nanataki, Tsutomu, Akao, Takayoshi, Ohwada, Iwao
• Primary Examiner(s): Nguyen, Chanh
• Assistant Examiner(s): Bell, Paul A.
• Application Number:
  US09/046,387
• Time in Patent Office: 1,345 Days
• Field of Search: 345/84, 345/85, 345/102, 345/108, 345/147, 345/148, 345/204, 385/1-10, 385/25, 385/30, 385/40, 385/41, 385/42, 385/129-133, 385/19, 385/147, 310/311, 310/328, 310/330, 310/331, 310/332, 310/324, 359/290-297
• US Class Current: 345/84
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3473 based on light coupled out of a light guide, e.g. due to scattering, by contracting the light guide with external means
• CPC Class Codes: G09G 3/3493 using light modulating elements actuated by a piezoelectric effect

Abstract

Disclosed is a display-driving device for driving a display comprising an optical waveguide plate for introducing light thereinto, and a driving section provided opposingly to one plate surface of the optical waveguide plate and including a number of actuator elements arranged corresponding to a large number of picture elements, for displaying, on the optical waveguide plate, a picture image corresponding to an image signal by controlling leakage light at a predetermined portion of the optical waveguide plate by controlling displacement action of each of the actuator elements in a direction to make contact or separation with respect to the optical waveguide plate in accordance with an attribute of the image signal to be inputted; the display-driving device comprising a row electrode-driving circuit for selecting the actuator elements at least in one row unit, a column electrode-driving circuit for outputting a data signal-to the selected row, and a signal control circuit for performing gradation control for the respective driving circuits in accordance with the temporal modulation system. Accordingly, it is possible to realize a simplified arrangement of a peripheral circuit system (including the driving circuits).

Claims

1. A display-driving device for driving a display comprising an optical waveguide plate for introducing light thereinto, and a driving section provided opposingly to one plate surface of said optical waveguide plate and including a number of actuator elements arranged corresponding to a large number of picture elements, for displaying, on said optical waveguide plate, a picture image corresponding to an image signal by controlling leakage light at a predetermined portion of said optical waveguide plate by controlling displacement action of each of said actuator elements in a direction to make contact or separation with respect to said optical waveguide plate in accordance with an attribute of said image signal to be inputted;

said display-driving device comprising a first driving circuit for selecting said actuator elements at least in one row unit, a second driving circuit for outputting displaying information to said selected row, and a signal control circuit for controlling said first and second driving circuits, wherein;

a display period for one image is assumed to be one field and one divided period obtained by dividing said one field into a plurality of divided ones is assumed to be a subfield;

an effective display period comprising a selection period and an unselection period is set for each subfield, said effective display period is set to have a temporal length corresponding to a unit gradation level allotted to said subfield; and

said first and second driving circuits are controlled to perform gradation control at least in accordance with a temporal modulation system by using said signal control circuit.

2. The display-driving device according to claim 1, wherein:

said actuator element of said display comprises a shape-retaining layer, an operating section having at least a pair of electrodes formed on said shape-retaining layer, a vibrating section for supporting said operating section, and a fixed section for supporting said vibrating section in a vibrating manner; and

said display comprises a displacement-transmitting section for transmitting said displacement action of said actuator element to said optical waveguide plate, said displacement action being generated by voltage application to said pair of electrodes.

3. The display-driving device according to claim 2, wherein said shape-retaining layer is a piezoelectric/electrostrictive layer.

4. The display-driving device according to claim 2, wherein said shape-retaining layer is an anti-ferroelectric layer.

5. The display-driving device according to claim 1, wherein at least a reset period, in which display brightness is substantially zero, is provided between said effective display period of a certain subfield and said effective display period of the next subfield.

6. The display-driving device according to claim 1, wherein:

at least one dummy subfield is provided in said one field in addition to said plurality of subfields; and

said dummy subfield has an effective display period which is constructed by only said selection period.

7. The display-driving device according to claim 6, wherein said signal control circuit makes control to selectively use said dummy subfield so that a number of said subfields to be used is increased substantially in a stepwise manner in accordance with increase in said gradation level.

8. The display-driving device according to claim 1, wherein a reset period and an unselection period, in which display brightness is substantially zero, are provided between said effective display period of a certain subfield and said effective display period of the next subfield.

9. The display-driving device according to claim 1, wherein a preparatory period is provided immediately before said selection period, in order to stabilize operation of said actuator element.

10. The display-driving device according to claim 1, wherein a preparatory period is provided during said selection period, in order to stabilize operation of said actuator element.

11. The display-driving device according to claim 1, wherein:

said first driving circuit is subjected to timing control by the aid of said signal control circuit so that all row selection is completed in each subfield; and

said second driving circuit is subjected to timing control by the aid of said signal control circuit so that a data signal, which is prepared by allotting a display time corresponding to each gradation level to said effective display period of each subfield, is outputted during said selection period in each subfield, for each picture element concerning said selected row.

12. The display-driving device according to claim 11, wherein said gradation level of each of said picture elements is a gradation level obtained by applying, to a gradation level obtained on the basis of said image signal, a predetermined operation processing with a conversion variable corresponding to a magnitude of dispersion with respect to a standard brightness.

13. The display-driving device according to claim 12, wherein said conversion variable is a variable which is used to converge said dispersion in brightness of each of said picture elements to a predetermined level, by applying said predetermined operation processing.

14. The display-driving device according to claim 11, wherein said first driving circuit is capable of setting at lest three voltage levels, and said second driving circuit is capable of setting at least two voltage levels.

15. The display-driving device according to claim 11, wherein:

said first driving circuit outputs a selection pulse signal during said selection period, it outputs an unselection signal during said unselection period, and it outputs a reset pulse signal during a reset period; and

said second driving circuit outputs an ON signal during said selection period in said effective display period of said allotted subfield of said respective subfields, and it outputs an OFF signal during said selection period of said effective display period of the other subfields.

16. The display-driving device according to claim 15, wherein:

a voltage, which is sufficient to make said bending displacement of said actuator element, is applied to said actuator element of said objective picture element during an output period of said ON signal; and

a voltage, which is sufficient to restore said displacement of said actuator element, is applied to said actuator element of said objective picture element during an output period of said reset pulse signal.

17. The display-driving device according to claim 16, wherein said first driving circuit outputs a selecting window pulse for applying, to said actuator element of said objective picture element, a voltage sufficient to allow said actuator element to make said bending displacement, by means of combination with said ON signal during said selection period.

18. The display-driving device according to claim 17, wherein said first driving circuit outputs a resetting window pulse for applying, to said actuator element of said objective picture element, a voltage sufficient to restore said displacement of said actuator element during said reset period.

19. The display-driving device according to claim 17, wherein said first driving circuit outputs an unselecting window pulse for decreasing a difference in average voltage applied during said unselection period, to said actuator element of each of said picture elements during said unselection period.

20. The display-driving device according to claim 15, wherein an absolute value of a difference between a maximum value of said voltage applied during said unselection period to said actuator element of each of said picture elements and a maximum value of said voltage applied by said OFF signal during said selection period is not more than 100% of an absolute value of a difference between a maximum value of said voltage applied by said ON signal during said selection period and a maximum value of said voltage applied by said OFF signal.

21. The display-driving device according to claim 15, wherein phase information is added to at least said ON signal so that a difference in average voltage applied during said unselection period is decreased for said actuator element of each of said picture elements.

22. The display-driving device according to claim 21, wherein said phase information is added to said selection pulse signal and said ON signal and/or said OFF signal respectively.

23. The display-driving device according to claim 21, wherein said phase information is also added to said reset signal in addition to said signals.

24. The display-driving device according to claim 21, wherein said ON signal and said OFF signal are allowed to have their respective pulse widths which are made to be smaller than an address time for said first driving circuit, and their respective phases are deviated from each other by a predetermined angle.

25. The display-driving device according to claim 15, wherein at least any one of said ON signal and said OFF signal has its pulse cycle which is 1/n of an address time, wherein n is an arbitrary real number from 1 to 5.

26. A display-driving method for driving a display comprising an optical waveguide plate for introducing light thereinto, and a driving section provided opposingly to one plate surface of said optical waveguide plate and including a number of actuator elements arranged corresponding to a large number of picture elements, for displaying, on said optical waveguide plate, a picture image corresponding to an image signal by controlling leakage light at a predetermined portion of said optical waveguide plate by controlling displacement action of each of said actuator elements in a direction to make contact or separation with respect to said optical waveguide plate in accordance with an attribute of said image signal to be inputted;

said display-driving method comprising the steps of;

assuming a display period for one image is one field;

assuming one divided period obtained by dividing said one field into a plurality of divided ones is a subfield;

setting an effective display period comprising a selection period and an unselection period for each subfield, said effective display period being set to have a temporal length corresponding to a unit gradation level allotted to said subfield;

selecting said actuator elements at least in one row unit;

outputting displaying information to said selected row; and

making gradation control for each of said picture elements at least in accordance with a temporal modulation system.

27. The display-driving method according to claim 26, wherein:

said actuator element of said display comprises a shape-retaining layer, an operating section having at least a pair of electrodes formed on said shape-retaining layer, a vibrating section for supporting said operating section, and a fixed section for supporting said vibrating section in a vibrating manner; and

said display comprises a displacement-transmitting section for transmitting said displacement action of said actuator element to said optical waveguide plate, said displacement action being generated by voltage application to said pair of electrodes.

28. The display-driving method according to claim 27, wherein said shape-retaining layer is a piezoelectric/electrostrictive layer.

29. The display-driving method according to claim 27, wherein said shape-retaining layer is an anti-ferroelectric layer.

30. The display-driving method according to claim 26, wherein at least a reset period, in which display brightness is substantially zero, is provided between said effective display period of a certain subfield and said effective display period of the next subfield.

31. The display-driving method according to claim 26, wherein:

at least one dummy subfield is provided in said one field in addition to said plurality of subfields; and

said dummy subfield has an effective display period which is constructed by only said selection period.

32. The display-driving method according to claim 31, wherein said dummy subfield is selectively used so that a number of said subfields to be used is increased substantially in a stepwise manner in accordance with increase in said gradation level.

33. The display-driving method according to claim 26, wherein a reset period and an unselection period, in which display brightness is substantially zero, are provided between said effective display period of a certain subfield and said effective display period of the next subfield.

34. The display-driving method according to claim 26, wherein a preparatory period is provided immediately before said selection period, in order to stabilize operation of said actuator element.

35. The display-driving method according to claim 26, wherein a preparatory period is provided during said selection period, in order to stabilize operation of said actuator element.

36. The display-driving method according to claim 26, wherein:

timing control is performed so that all row selection is completed in each subfield; and

timing control is performed so that a data signal, which is prepared by allotting a display time corresponding to each gradation level to said effective display period of each subfield, is outputted during said selection period in each subfield, for each picture element concerning said selected row.

37. The display-driving method according to claim 36, wherein said gradation level of each of said picture elements is a gradation level obtained by applying, to a gradation level obtained on the basis of said image signal, a predetermined operation processing with a conversion variable corresponding to a magnitude of dispersion with respect to a standard brightness of said picture element.

38. The display-driving method according to claim 37, wherein said conversion variable is a variable which is used to converge said dispersion in brightness of each of said picture elements to a predetermined level, by applying said predetermined operation processing.

39. The display-driving method according to claim 36, wherein upon said row selection, at lest three voltage levels are allowed to be set, and upon said output of said displaying information, at least two voltage levels are allowed to be set.

40. The display-driving method according to claim 36, wherein:

said row selection is effected by outputting a selection pulse signal during said selection period, outputting an unselection signal during said unselection period, and outputting a reset pulse signal during a reset period; and

said output of displaying information is effected by outputting an ON signal during said selection period in said effective display period of said allotted subfield of said respective subfields, and outputting an OFF signal during said selection period of said effective display period of the other subfields.

41. The display-driving method according to claim 40, wherein:

a voltage, which is sufficient to make said bending displacement of said actuator element, is applied to said actuator element of said objective picture element during an output period of said ON signal; and

a voltage, which is sufficient to restore said displacement of said actuator element, is applied to said actuator element of said objective picture element during an output period of said reset pulse signal.

42. The display-driving method according to claim 41, wherein a selecting window pulse for applying, to said actuator element of said objective picture element, a voltage sufficient to allow said actuator element to make said bending displacement is outputted by means of combination with said ON signal during said selection period.

43. The display-driving method according to claim 42, wherein a resetting window pulse for applying, to said actuator element of said objective picture element, a voltage sufficient to restore said displacement of said actuator element is outputted during said reset period.

44. The display-driving method according to claim 42, wherein an unselecting window pulse for decreasing a difference in average voltage applied during said unselection period is outputted to said actuator element of each of said picture elements during said unselection period.

45. The display-driving method according to claim 40, wherein an absolute value of a difference between a maximum value of said voltage applied during said unselection period to said actuator element of each of said picture elements and a maximum value of said voltage applied by said OFF signal during said selection period is not more than 100% of an absolute value of a difference between a maximum value of said voltage applied by said ON signal during said selection period and a maximum value of said voltage applied by said OFF signal.

46. The display-driving method according to claim 40, wherein phase information is added to at least said ON signal so that a difference in average voltage applied during said unselection period is decreased for said actuator element of each of said picture elements.

47. The display-driving method according to claim 46, wherein said phase information is added to said selection pulse signal and said ON signal and/or said OFF signal respectively.

48. The display-driving method according to claim 46, wherein said phase information is also added to said reset signal in addition to said signals.

49. The display-driving method according to claim 46, wherein said ON signal and said OFF signal are allowed to have their respective pulse widths which are made to be smaller than an address time for said row selection, and their respective phases are deviated from each other by a predetermined angle.

50. The display-driving method according to claim 40, wherein at least any one of said ON signal and said OFF signal has its pulse cycle which is 1/n of said address time, wherein n is an arbitrary real number from 1 to 5.

51. A display-driving device for driving a display comprising an optical waveguide plate for introducing light thereinto, and a driving section provided opposingly to one plate surface of said optical waveguide plate and including a number of actuator elements arranged corresponding to a large number of picture elements, for displaying, on said optical waveguide plate, a picture image corresponding to an image signal by controlling leakage light at a predetermined portion of said optical waveguide plate by controlling displacement action of each of said actuator elements in a direction to make contact or separation with respect to said optical waveguide plate in accordance with an attribute of said image signal to be inputted;

said display-driving device comprising a first driving circuit for selecting said actuator elements at least in one row unit, a second driving circuit for outputting displaying information to said selected row, and a signal control circuit for controlling said first and second driving circuits, wherein;

said first and second driving circuits are controlled to perform gradation control at least in accordance with a temporal modulation system by using said signal control circuit; and

said first and second driving circuits are controlled to apply alternating polarity voltages of sufficient magnitude to each of said actuator elements such that said actuator elements exhibit hysteresis bending displacement whereby each of said actuator elements assumes two different displacement positions at a single predetermined voltage applied thereto.

52. The display-driving device according to claim 51, wherein:

each said actuator element of said display comprises a shape-retaining layer, an operating section having at least a pair of electrodes formed on said shape-retaining layer, a vibrating section for supporting said operating section, and a fixed section for supporting said vibrating section in a vibrating manner; and

said display comprises a displacement-transmitting section for transmitting said displacement action of said actuator element to said optical waveguide plate, said displacement action being generated by voltage application to said pair of electrodes.

53. The display-driving device according to claim 52, wherein said shape-retaining layer is a piezoelectric/electrostrictive layer.

54. The display-driving device according to claim 52, wherein said shape-retaining layer is an anti-ferroelectric layer.

55. The display-driving device according to claim 51, wherein a display period for one image is assumed to be one field, and an effective display period comprising a selection period and an unselection period is set within said period.

56. A display-driving method for driving a display comprising an optical waveguide plate for introducing light thereinto, and a driving section provided opposingly to one plate surface of said optical waveguide plate and including a number of actuator elements arranged corresponding to a large number of picture elements, for displaying, on said optical waveguide plate, a picture image corresponding to an image signal by controlling leakage light at a predetermined portion of said optical waveguide plate by controlling displacement action of each of said actuator elements in a direction to make contact or separation with respect to said optical waveguide plate in accordance with an attribute of said image signal to be inputted;

said display-driving method comprising the steps of;

selecting said actuator elements at least in one unit row;

outputting displaying information to said selected row;

making gradation control for each of said picture elements at least in accordance with a temporal modulation system; and

applying alternating polarity voltages of sufficient magnitude to each of said actuator elements such that said actuator elements exhibit hysteresis bending displacement whereby each of said actuator elements assumes two different displacement positions at a single predetermined voltage applied thereto.

57. The display-driving method according to claim 56, wherein:

each said actuator element of said display comprises a shape-retaining layer, an operating section having at least a pair of electrodes formed on said shape-retaining layer, a vibrating section for supporting said operating section, and a fixed section for supporting said vibrating section in a vibrating manner; and

said display comprises a displacement-transmitting section for transmitting said displacement action of said actuator element to said optical waveguide plate, said displacement action being generated by voltage application to said pair of electrodes.

58. The display driving method according to claim 57, wherein said shape-retaining layer is a piezoelectric/electrostrictive layer.

59. The display-driving method according to claim 57, wherein said shape-retaining layer is an anti-ferroelectric layer.

60. The display-driving method according to claim 56, wherein a display period for one image is assumed to be one field, and an effective display period comprising a selection period and an unselection period is set during said period.