Low power LCD with gray shade driving scheme

• US 7,362,294 B2
• Filed: 09/27/2002
• Issued: 04/22/2008
• Est. Priority Date: 04/26/2000
• Status: Expired due to Fees

• Current Assignee: JPS Group Holdings Incorporated
• Original Assignee: JPS Group Holdings, Ltd. (UltraChip, Inc.)
• Inventors: Shih-Hsin, Juan, Liang, Jemm Y., Xiao, Peter
• Primary Examiner(s): Liang; Regina
• Application Number:
  US10/256,687
• Publication Number:
  US 20030034946A1
• Time in Patent Office: 2,034 Days
• Field of Search: 345/89, 345/87, 345 94- 96, 345/99, 345/100, 345/204, 345208-210, 345690-693, 348790-793
• US Class Current: 345/89
• CPC Class Codes: G09G 2310/02 Addressing, scanning or driving the display screen or processing steps related thereto
• CPC Class Codes: G09G 2310/0205 Simultaneous scanning of several lines in flat panels
• CPC Class Codes: G09G 2310/0213 controlling the sequence of the scanning lines with respect to the patterns to be displayed, e.g. to save power
• 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 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/023 using energy recovery or conservation
• CPC Class Codes: G09G 3/2029 the sub-frames having non-binary weights
• CPC Class Codes: G09G 3/3622 using a passive matrix G09G3/3674 - G09G3/3696 take precedence

Abstract

In a passive liquid crystal display, frames or fields are displayed for different time periods to achieve gray scale. The voltage pulses applied to the column electrodes have substantially constant values during row scanning periods or field scanning periods to reduce power consumption. The lines of the display may be divided into odd and even fields in an interlaced configuration to suppress flicker and to further reduce power consumption by reducing frame rate.

Claims

1. A method for displaying gray shade images in a liquid crystal display, said display comprising an array of elongated row electrodes and an array of elongated column electrodes arranged transverse to the row electrodes, wherein overlapping areas of the two arrays of electrodes define pixels of the display when viewed in a viewing direction, comprising:

applying electrical potentials to the two arrays of electrodes to display different repetitive frames or fields, wherein an image is displayed by addressing the row and column electrodes during sequential row addressing time periods, and wherein during each of the row addressing time periods, a substantially constant row selection potential is applied to at least a selected one of the row electrodes for displaying an image at a line of pixels overlapping the at least one selected row electrode, each frame being the total number of lines in a displayed image of the display, and each field being a collection of lines displayed consecutively in the displayed image, wherein the collection of lines is a subset of and contains fewer than the lines that form the displayed image, at least one of said repetitive frames or fields having at least two different corresponding row electrode addressing periods for at least two corresponding sets of lines within such frame or field, thereby causing display of desired images, wherein, for displaying at least one of a number of different gray shades in the desired images, the electrical potentials are applied so that the at least two corresponding row electrode addressing periods of the at least two corresponding sets of lines of the at least one repetitive frame or field displayed are of different non-zero lengths of time.

2. The method of claim 1, each of said repetitive fields having a corresponding row electrode addressing period during which a row selection potential is applied to at least one selected row electrode for displaying an image at at least one line of pixels overlapping said at least one selected row electrode, wherein the electrical potentials are applied so that at least two of the repetitive fields have different row electrode addressing periods.

3. The method of claim 2, wherein the electrical potentials arc applied so that at least three of the repetitive fields have different row electrode addressing periods and values of row electrode addressing periods of the at least three different repetitive fields form integer ratios relative to each other.

4. The method of claim 3, wherein values of row electrode addressing periods of repetitive fields form integer ratios relative to each other of the following ratios:

2;

3;

4, 7;

9;

11;

12;

13, 6;

9;

11;

12;

13 or 3;

4;

5;

6.

5. The method of claim 2, wherein the electrical potentials are applied so that at least three of the repetitive fields have different row electrode addressing periods and such fields are applied in a sequence of ascending order of their row electrode addressing periods.

6. The method of claim 2, wherein the electrical potentials are applied so that at least three of the repetitive fields have different row electrode addressing periods and such fields are applied in a sequence of ascending order of their row electrode addressing periods, so that a value at or near the end of the sequence is not more than about 2.5 times a value at or near the beginning of the sequence.

7. The method of claim 6, wherein the value at or near the end of the sequence is not more than about 2.2 times the value at or near the beginning of the sequence.

8. The method of claim 6, wherein the value at or near the end of the sequence is not more than about 2.0 times the value at or near the beginning of the sequence.

9. The method of claim 6, wherein the applying is such that images with more than 30 gray shades are displayed by the liquid crystal display.

10. The method of claim 6, wherein the applying is such that substantially the same electrical potential(s) are applied to the column electrodes during each of the row electrode addressing periods.

11. The method of claim 2, wherein the electrical potentials are applied so that at least three of the repetitive fields have different row electrode addressing periods and such fields are applied in a sequence of ascending order of their row electrode addressing periods, so that the row electrode addressing periods are such that differences between pairs of adjacent values in the sequence decrease from the beginning of the sequence towards the end of the sequence.

12. The method of claim 2, wherein said decrease of the differences between pairs of adjacent values in the sequence is monotonic from the beginning of the sequence towards the end of the sequence.

13. The method of claim 2, wherein said applying is such that 3 repetitive fields are displayed, and wherein values of row electrode addressing periods of repetitive fields form integer ratios relative to each other of the following ratios:

2;

X;

2, where X is a positive number, so that the application of the electrical potentials results in 4 gray shades.

14. The method of claim 2, wherein said applying is such that 3 repetitive fields are displayed, and wherein values of row electrode addressing periods of repetitive fields form integer ratios relative to each other of the following ratios:

2;

3;

4 so that the application of the electrical potentials results in 8 gray shades.

15. The method of claim 2, wherein said applying is such that 4 repetitive fields are displayed, and wherein values of row electrode addressing periods of repetitive fields form integer ratios relative to each other of the following ratios:

3;

4;

5;

6 so that the application of the electrical potentials results in 15 gray shades.

16. The method of claim 2, wherein said applying is such that 5 repetitive fields are displayed, and wherein values of row electrode addressing periods of repetitive fields form integer ratios relative to each other of one of the following ratios:

7;

9;

11;

12;

13, so that the application of the electrical potentials results in 16 gray shades.

17. The method of claim 2, wherein said applying is such that 5 repetitive fields are displayed, and wherein values of row electrode addressing periods of repetitive fields form integer ratio relative to each other of 6:

9;

11;

12;

13, so that the application of the electrical potentials results in 32 gray shades.

18. The method of claim 1, said desired images comprising lines each of which corresponding to one of the row electrodes, wherein the applying causes repetitive fields to be displayed, and wherein each of at least two of the repetitive fields contains less than all of the lines of said desired images.

19. The method of claim 18, said desired images comprising lines, wherein said at least two of the repetitive fields contain complementary lines of said desired images.

20. The method of claim 18, said desired images comprising lines, wherein at least one set of three or four of the repetitive fields contain lines that together contain all the lines of said desired images.

21. The method of claim 18, wherein the applying applies electrical potentials so that lines of each of said at least two repetitive fields are displayed during a different corresponding field scanning period.

22. The method of claim 21, wherein the lines of said at least two repetitive fields are interleaved with one another.

23. The method of claim 22, wherein the lines of said at least two repetitive fields constitute all of the lines of said desired images, one of said at least two repetitive fields containing odd numbered lines and the other of said at least two repetitive fields containing even numbered lines, wherein the odd lines are displayed during odd field scanning periods and even lines are displayed during even field scanning periods.

24. The method of claim 23, wherein the applying applies to the column electrodes electrical potentials that are substantially unchanged during each of at least some of the field scanning periods.

25. The method of claim 23, wherein the applying applies electrical potentials to the row electrodes for time periods in accordance with a time sequence of different row electrode addressing periods.

26. The method of claim 25, wherein the applying applies to the row electrodes electrical potentials that of a first polarity during a first half of a full addressing cycle, and electrical potentials that of a second polarity during a second half of the full addressing cycle, in accordance with the time sequence.

27. The method of claim 25, wherein the applying applies to the row electrodes electrical potentials of opposite polarities during a full addressing cycle, and wherein electrical potentials of opposite polarities are applied for the same row electrode addressing period substantially half of a full addressing cycle apart.

28. The method of claim 25, wherein the applying is such that electrical potentials applied during the longest and shortest time periods in the sequence are applied consecutively in time with one immediately following the other.

29. The method of claim 22, wherein the at least two repetitive fields comprise n repetitive fields that in combination contain all of the lines of said desired images, n being an integer greater than 1, and the applying applies signal pulses that cause lines in the n different fields to be displayed for substantially the same row addressing time period during a full addressing cycle T or (½

)T, and wherein the application of such signal pulses to cause the display of physically adjacent lines in different fields are spaced apart in time by integral multiples of T/2n, thereby increasing a line rate as observed by an observer.

30. The method of claim 22, wherein the at least two repetitive fields comprise odd and even fields, and the applying applies signal pulses that cause lines in the odd and even fields to be displayed for substantially the same row addressing time period during a full addressing cycle T or T/2, and wherein the application of such signal pulses to cause the display of physically side-by-side pixel lines in different fields are spaced apart in time by integral multiples of T/4, thereby increasing a line rate as observed by an observer.

31. The method of claim 18, wherein the lines in at least one field are divided into subsets, and the applying applies signal pulses to cause corresponding subsets of lines to be displayed, and wherein the signal pulses applied to cause the display of two different subsets of lines are applied for different row addressing time periods.

32. The method of claim 2, each of said repetitive fields having a corresponding row electrode addressing period during which a row selection potential is applied to two or more selected row electrodes for displaying an image at two or more corresponding lines of pixels overlapping said two or more selected row electrodes.

33. The method of claim 32, wherein no pulse width modulation is employed in generating the electrical potentials for displaying gray shades.

34. The method of claim 1, wherein the applying causes non-linear gray shades to be displayed.

35. The method of claim 34, wherein the gray shades are spaced apart by steps and the steps between adjacent gray shades in a gray scale are smaller for gray shades away from ends of the scale than those at or near the ends of the scale.

36. The method of claim 1, each of said repetitive fields having a plurality of corresponding row electrode addressing periods during each of which a row selection potential is applied to at least one selected row electrode for displaying an image at at least one line of pixels overlapping said at least one selected row electrode, wherein substantially the same electrical potentials are applied to the column electrodes during each of at least some of the row electrode addressing periods of at least one of said repetitive fields.

37. A method for displaying gray shade images in a liquid crystal display, said display comprising an array of elongated row and an array of elongated column electrodes arranged transverse to the row electrodes, wherein overlapping areas of the two arrays of electrodes define pixels of the display when viewed in a viewing direction, comprising:

applying electrical potentials to the two arrays of electrodes to display two or more different frames, each of the frames divided into two or more fields, thereby causing display of desired images, said desired images comprising lines corresponding to the row electrodes, wherein the electrical potentials are applied so that at least two of the fields each containing less than all the lines of said desired images are displayed repetitively, at least one of said repetitively displayed fields having at least two corresponding row electrode addressing periods for at least two corresponding sets of lines within such field, thereby causing display of desired images, wherein, for displaying at least one of a number of different gray shades in the desired images, the electrical potentials are applied so that the at least two corresponding row electrode addressing periods of the at least two corresponding sets of lines of the at least one repetitively displayed field displayed are of different non-zero lengths of time.

38. The method of claim 37, wherein said at least two of the repetitive fields contain complementary lines of said desired images.

39. The method of claim 37, wherein for displaying at least one of a number of different gray shades in the desired images the repetitive fields are displayed for different time periods.

40. The method of claim 37, wherein the applying applies electrical potentials so that lines of each of said at least two repetitive fields are displayed during a different corresponding field scanning period.

41. The method of claim 40, wherein the lines of said at least two repetitive fields from the same frame are interleaved with one another.

42. The method of claim 41, wherein the at least two repetitive fields comprise n repetitive fields that in combination contain all of the lines of said desired images, n being an integer greater than 1, and the applying applies signal pulses that cause lines in the n different fields to be displayed for substantially the same row addressing time period during a full addressing cycle T or T/2, and wherein the application of such signal pulses to cause the display of physically adjacent lines in different fields are spaced apart in time by integral multiples of T/2n, thereby increasing a line rate as observed by an observer.

43. The method of claim 41, wherein the at least two repetitive fields comprise odd and even fields, and the applying applies signal pulses that cause lines in the odd and even fields to be displayed for substantially the same row addressing time period during a full addressing cycle T/2 or T, and wherein the application of such signal pulses to cause the display of physically adjacent lines in different fields are spaced apart in time by integral multiples of T/4, thereby increasing a line rate as observed by an observer.

44. The method of claim 41, wherein the lines of said at least two repetitive fields constitute all of the lines of said desired images, one of said at least two repetitive fields containing odd numbered lines and the other of said at least two repetitive fields containing even numbered lines, wherein the odd lines are displayed during odd field scanning periods and even lines are displayed during even field scanning periods.

45. The method of claim 40, wherein the applying applies to the column electrodes electrical potentials that are substantially unchanged during each of at least some of the field scanning periods.

46. The method of claim 40, wherein the applying applies electrical potentials to the row electrodes for time periods in accordance with a time sequence of different row electrode addressing periods.

47. The method of claim 40, wherein the applying applies to the row electrodes electrical potentials that of a first polarity during a first half of a full addressing cycle, and electrical potentials that of a second polarity during a second half of the full addressing cycle, in accordance with the time sequence.

48. The method of claim 40, wherein the applying applies to the row electrodes electrical potentials of opposite polarities during a full addressing cycle, and wherein electrical potentials of opposite polarities are applied for the same row electrode addressing period substantially half of a full addressing cycle apart.

49. The method of claim 40, wherein the applying is such that electrical potentials applied during the longest and shortest time periods in the sequence are applied consecutively in time.

50. The method of claim 37, wherein at least one set of three or four of the repetitive fields contain lines that together contain all the lines of said desired images.

51. The method of claim 37, wherein the applying causes non-linear gray shades to be displayed.

52. The method of claim 51, wherein the gray shades are spaced apart by steps and the steps between adjacent gray shades in a gray scale are smaller for gray shades away from ends of the scale than those at or near the ends of the scale.

53. The method of claim 37, each of said repetitive fields having a plurality of corresponding row electrode addressing periods during each of which a row selection potential is applied to at least one selected row electrode for displaying an image at at least one line of pixel overlapping said at least one selected row electrode, wherein substantially the same electrical potentials are applied to the column electrodes during each of at least some of the row electrode addressing periods of at least one of said repetitive fields.

54. The method of claim 37, wherein the lines of said at least two repetitive fields constitute all of the lines of said desired images, one of said at least two repetitive fields containing odd numbered lines and the other of said at least two repetitive fields containing even numbered lines, wherein the odd lines are displayed during odd field scanning periods and even lines are displayed during even field scanning periods.

55. The method of claim 54, wherein the applying applies in the odd or even field pulses of electrical potentials to the row electrodes at times that each of at least some of which is substantially half way in time between consecutive pulses of the other field.

56. The method of claim 55, wherein the applying applies electrical potentials to the row electrodes for different time periods in accordance with a time sequence of different time periods.

57. The method of claim 56, wherein for each of the time periods in the sequence, the applying applies in the odd or even field pulses of electrical potentials to the row electrodes at times that each of which is substantially half way in time between consecutive pulses of the other field.

58. The method of claim 37, wherein the lines in at least one field are divided into subsets, and the applying applies signal pulses to cause corresponding subsets of lines to be displayed, and wherein the signal pulses applied to cause the display of two different subsets of lines are applied for different row addressing time periods.

59. The method of claim 37, each of said fields having a corresponding row electrode addressing period during which a row selection potential is applied to at least one selected row electrode for displaying an image at at least one line of pixels overlapping said at least one selected row electrode, wherein the electrical potentials are applied so that at least two of the fields have different row electrode addressing periods.

60. The method of claim 59, each of said fields having a corresponding row electrode addressing period during which a row selection potential is applied to two or more selected row electrodes for displaying an image at two or more corresponding lines of pixels overlapping said two or more selected row electrodes.

61. The method of claim 60, wherein no pulse width modulation is employed in generating the electrical potentials for displaying gray shades.

62. An apparatus for displaying gray shade images comprising:

a liquid crystal display comprising an array of elongated row and an array of elongated column electrodes arranged transverse to the row electrodes, wherein overlapping areas of the two arrays of electrodes define pixels of the display when viewed in a viewing direction; and

a drive circuit applying electrical potentials to the two arrays of electrodes to display repetitive frames or fields, wherein an image is displayed by addressing the row and column electrodes during sequential row addressing time periods, and wherein during each of the row addressing time periods, a substantially constant row selection potential is applied to at least a selected one of the row electrodes for displaying an image at a line of pixels overlapping the at least one selected row electrode, at least one of said repetitive frames or fields having at least two corresponding row electrode addressing periods for at least two corresponding sets of lines within such frame or field, thereby causing display of desired images, each frame being the total number of lines in a desired image of the display, and each field being a collection of lines in the desired image, wherein the collection of lines is a subset of and contains fewer than the lines that form the desired image, wherein, for displaying at least one of a number of different gray shades in the desired images, the electrical potentials are applied so that the at least two corresponding row electrode addressing periods of the at least two corresponding sets of lines of the at least one repetitive frame or field displayed are for different non-zero lengths of time.

63. An apparatus for displaying gray shade images, comprising:

a liquid crystal display comprising an array of elongated row and an array of elongated column electrodes arranged transverse to the row electrodes, wherein overlapping areas of the two arrays of electrodes define pixels of the display when viewed in a viewing direction; and

a drive circuit applying electrical potentials to the two arrays of electrodes to display two or more different frames, each of the frames divided into two or more fields, thereby causing display of desired images, said desired images comprising lines, wherein the electrical potentials are applied so that the two or more fields are applied for different time periods and wherein at least two of the fields each containing less than all the lines of said desired images are displayed repetitively, at least one of said repetitively displayed fields having at least two corresponding row electrode addressing periods for at least two corresponding sets of lines within such field, thereby causing display of desired images, wherein, for displaying at least one of a number of different gray shades in the desired images, the electrical potentials are applied so that the at least two corresponding row electrode addressing periods of the at least two corresponding sets of lines of the at least one repetitively displayed field are of different non-zero lengths of time.

64. A method for displaying gray shade images in a liquid crystal display, said display comprising an array of elongated row electrodes and an array of elongated column electrodes arranged transverse to the row electrodes, wherein overlapping areas of the two arrays of electrodes define pixels of the display when viewed in a viewing direction, comprising:

applying electrical potentials to the two arrays of electrodes to display different repetitive frames or fields, each repetitive frame or field having at least one corresponding row electrode addressing period, thereby causing display of desired images, each repetitive frame being the total number of lines in a desired image of the display, and each repetitive field being a collection of lines in the desired image, wherein the collection of lines is a subset of and contains fewer than the lines that form the desired image, wherein, for displaying at least one of a number of different gray shades in the desired images, the electrical potentials are applied so that the corresponding row electrode addressing periods of each of at least three of the repetitive frames or fields have different row electrode addressing periods, form integer ratios relative to each other, and such frames or fields are applied in a sequence in ascending order.

65. A method for displaying gray shade images in a liquid crystal display, said display comprising an array of elongated row electrodes and an array of elongated column electrodes arranged transverse to the row electrodes, wherein overlapping areas of the two arrays of electrodes define pixels of the display when viewed in a viewing direction, comprising:

applying electrical potentials to the two arrays of electrodes to display different repetitive frames or fields, each repetitive frame or field having a plurality of corresponding row electrode addressing periods, thereby causing display of desired images, each repetitive frame being the total number of lines in a desired image of the display, and each repetitive field being a collection of lines in the desired image, wherein the collection of lines is a subset of and contains fewer than the lines that form the desired image, wherein, for displaying at least one of a number of different gray shades in the desired images, the electrical potentials are applied so that the corresponding row electrode addressing periods of each of at least three of the repetitive frames or fields are different and such frames or fields are applied in a sequence of ascending order of their row electrode addressing periods, so that a value at or near the end of the sequence is not more than about 2.5 times a value at or near the beginning of the sequence.

66. The method of claim 65, wherein the value at or near the end of the sequence is not more than about 2.2 times the value at or near the beginning of the sequence.

67. The method of claim 66, wherein the value at or near the end of the sequence is not more than about 2.0 times the value at or near the beginning of the sequence.

68. The method of claim 65, wherein the applying is such that images with more than 30 gray shades are displayed by the liquid crystal display.

69. The method of claim 65, wherein the applying is such that substantially the same electrical potential(s) are applied to the column electrodes during each of the row electrode addressing periods.

70. The method of claim 65, wherein when the values of row electrode addressing periods of the at least three different repetitive fields are applied in a sequence in ascending order, the row electrode addressing periods are such that differences between pairs of adjacent values in the sequence decrease from the beginning of the sequence towards the end of the sequence.

71. The method of claim 70, wherein said decrease is monotonic from the beginning of the sequence towards the end of the sequence.

72. The method of claim 65, wherein a difference between each pair of adjacent values at or near the end of the sequence is substantially equal to a maximum common denominator of the values.

73. A method for displaying gray shade images in a liquid crystal display, said display comprising an array of elongated row electrodes and an array of elongated column electrodes arranged transverse to the row electrodes, wherein overlapping areas of the two arrays of electrodes define pixels of the display when viewed in a viewing direction, comprising:

applying electrical potentials to the two arrays of electrodes to display different repetitive frames or fields, each repetitive frame or field having at least one corresponding row electrode addressing period, thereby causing display of desired images, each repetitive frame being the total number of lines in a desired image of the display, and each repetitive field being a collection of lines in the desired image, wherein the collection of lines is a subset of and contains fewer than the lines that form the desired image, wherein, for displaying at least one of a number of different gray shades in the desired images, the electrical potentials are applied so that the corresponding row electrode addressing periods of each of at least three of the repetitive frames or fields have different row electrode addressing periods and form integer ratios relative to each other, and such frames or fields are applied in a sequence of ascending order of their row electrode addressing periods, so that differences between pairs of adjacent values in the sequence decrease from the beginning of the sequence towards the end of the sequence.

74. The method of claim 73, wherein said decrease is monotonic from the beginning of the sequence towards the end of the sequence.