Method and apparatus for controlling pixel emission

• US 20070069998A1
• Filed: 06/17/2004
• Published: 03/29/2007
• Est. Priority Date: 06/18/2003
• Status: Abandoned Application

• Current Assignee: Leadin Technology Co., Ltd.
• Original Assignee: Leadin Technology Co., Ltd.
• Inventors: Naugler, W. Edward, Reddy, Diamoder
• Application Number:
  US10/515,575
• Publication Number:
  US 20070069998A1
• Time in Patent Office: Days
• US Class Current: 345/81
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0259 with use of an analog or digital ramp generator in the column driver or in the pixel circuit
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/066 Waveforms comprising a gently increasing or decreasing portion, e.g. ramp
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/147 the originated light output being determined for each pixel
• CPC Class Codes: G09G 2360/148 the light being detected by light detection means within each pixel
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

Emission from a pixel is received by a sensor. The sensor is coupled to a control unit that receives or determines a value of the sensor'"'"'s measurable parameter during operation of the pixel. A target value is coupled to the control unit, allowing the control unit to compare the measurable sensor parameter and the target value. The control unit is coupled to a pixel driver operable to alter the emission from the pixel. The pixel driver may vary the emission from the pixel until the measurable sensor parameter indicates that the target value has been achieved. The target value may be determined based on a calibration of the sensor. A plurality of target values may be stored in a look-up table. Passive and active matrix displays may be controlled in accordance with methods and apparatuses of the invention.

Claims

1. A method for controlling emission from a pixel using a pixel driver and a sensor having a measurable sensor parameter to achieve a predetermined emission level, the method comprising:

varying light emission from the pixel using the pixel driver;

receiving light emission from the pixel at the sensor;

obtaining a measured value of the measurable sensor parameter responsive to the received light emission;

coupling the measured value to the pixel driver; and

generating a control signal for the pixel to maintain constant emission from the light source at the predetermined emission level.

2. A method according to claim 1, wherein the pixel includes a light source.

3. A method according to claim 1, wherein the pixel driver provides a voltage to the pixel.

4. A method according to claim 1, wherein the pixel driver is not contained within the pixel.

5. A method according to claim 1, wherein the pixel is a pixel of a liquid crystal display.

6. A method according to claim 2, wherein the light source includes a light emitting diode.

7. A method according to claim 2, wherein the light source includes a white light emitting diode.

8. A method according to claim 2, wherein the light source includes an organic light emitting diode.

9. A method according to claim 1, wherein the sensor includes a light-sensitive resistor, optical diode, or optical transistor.

10. A method according to claim 1, wherein the sensor includes a light-sensitive resistor and the measurable sensor parameter includes a voltage across the resistor.

11. A method according to claim 1, further comprising comparing the measured value to a reference value of the measurable sensor parameter, the reference value indicative of the predetermined emission level.

12. A method according to claim 11, wherein the reference value is an image voltage.

13. A method according to claim 11, further comprising calibrating the sensor to determine the reference value.

14. A method according to claim 13, wherein the act of calibrating the sensor comprises illuminating the sensor with a calibration light source.

15. A method according to claim 2, wherein the light source is a pixel of a display.

16. A method according to claim 1, wherein the light source is an organic light emitting diode and the act of generating a control signal includes increasing a current through the light emitting diode.

17. A method according to claim 11, wherein the act of comparing the measured value with the reference value includes coupling the measured value and the predetermined value to a comparator.

18. A method according to claim 1, wherein the pixel driver provides a varying signal to the pixel to cause increasing light emission from the pixel and wherein the act of generating a control signal comprises replacing the varying signal with a constant signal to cause stable light emission from the light source.

19. A method according to claim 18 wherein the varying signal comprises a ramp signal.

20. A method according to claim 19, wherein the ramp signal comprises a voltage ramp.

21. An apparatus for controlling emission from a pixel to achieve a predetermined emission level, the apparatus comprising:

a sensor having a measurable sensor parameter positioned to receive at least a portion of the radiation emitted from the pixel;

a pixel driver coupleable to the pixel for varying the light emission from the pixel; and

a control unit coupled to the sensor and operable to couple a control signal to the pixel driver to maintain constant emission from the pixel when the predetermined emission level is attained.

22. An apparatus according to claim 21, the control unit further coupled to a reference signal indicative of the value of the measurable sensor parameter during the predetermined emission level, the control unit operable to compare the reference signal and the measured value.

23. An apparatus according to claim 21 further comprising a calibration look-up table coupled to the control unit, the calibration look-up table storing at least one value of the measurable sensor parameter indicative of the predetermined emission level.

24. A controlled pixel system, the system comprising:

a pixel element;

a sensor having a measurable sensor parameter positioned to receive at least a portion of the radiation emitted from the pixel;

a pixel driver coupled to the pixel, the pixel driver operable to supply a drive signal to the pixel to vary light emission from the pixel; and

a control unit coupled to the pixel driver and the sensor, the control unit operable to determine, based on a measured value of the measurable sensor parameter, the predetermined emission level is attained and develop a control signal for the pixel driver to maintain constant light emission at the predetermined emission level.

25. A controlled pixel system according to claim 24, wherein the pixel element is formed in a first area and the pixel driver is outside the first area.

26. A controlled pixel system according to claim 24, wherein the pixel driver provides a varying signal to the pixel.

27. A controlled pixel system according to claim 24, wherein said control unit is further coupled to a reference signal indicative of the predetermined emission level, the control unit further operable to compare the measured value of the measurable sensor parameter with the reference signal to determine the predetermined emission level is attained.

28. A controlled pixel system according to claim 24, wherein said sensor includes a photo-sensitive resistor, diode, or transistor.

29. A controlled pixel system according to claim 24, further comprising a plurality of pixel elements.

30. A method of controlling an array of pixels in an active matrix display to a predetermined emission level, the pixels arranged in a plurality of rows and a plurality of columns, each pixel having an active matrix element, the method using a plurality of sensors each having a measurable sensor parameter and at least one pixel driver, the method comprising:

varying light emission from a plurality of pixels in a first row using the at least one pixel driver and the active matrix elements;

receiving light emission from the plurality of pixels at the plurality of sensors;

obtaining a measured value of the measurable sensor parameter for each of the plurality of sensors responsive to the received light emission; and

for each of the plurality of pixels, generating a control signal for the pixel to maintain constant emission from the light source at the predetermined emission level.

31. A method according to claim 30, wherein each of the plurality of pixels include a light source.

32. A method according to claim 30, wherein the at least one pixel driver provides a voltage to each of the plurality of pixels.

33. A method according to claim 30, wherein the plurality of pixels are pixels of a liquid crystal display.

34. A method according to claim 31, wherein the light source includes a light emitting diode.

35. A method according to claim 31, wherein the light source includes a white light emitting diode.

36. A method according to claim 31, wherein the light source includes an organic light emitting diode, electroluminescence, plasma emission, field emission, or vacuum florescence.

37. A method according to claim 30, wherein each of the plurality of sensors include a light-sensitive resistor, optical diode, or optical transistor.

38. A method according to claim 30, wherein at least one of the plurality of sensors includes a light-sensitive resistor and the measurable sensor parameter includes a voltage across the resistor.

39. A method according to claim 30, further comprising comparing the measured value to a reference value of the measurable sensor parameter, the reference value indicative of the predetermined emission level.

40. A method according to claim 39, wherein the reference value is an image voltage.

41. A method according to claim 40, further comprising calibrating the sensor to determine the reference value.

42. A method according to claim 41, wherein the act of calibrating the sensor comprises illuminating the sensor with a calibration light source.

43. A method according to claim 31, wherein the light source is an organic light emitting diode and the act of generating a control signal includes increasing a current through the light emitting diode.

44. A method according to claim 39, wherein the act of comparing the measured value with the reference value includes coupling the measured value and the predetermined value to a comparator.

45. A method according to claim 30, wherein the pixel driver provides a varying signal to the pixel to cause increasing light emission from the pixel and wherein the act of generating a control signal comprises replacing the varying signal with a constant signal to cause stable light emission from the pixel.

46. A method according to claim 45, wherein the varying signal comprises a ramp signal.

47. A method according to claim 46, wherein the ramp signal comprises a voltage ramp.

48. A method according to claim 46, wherein the ramp signal comprises a step voltage

49. A method according to claim 30, further comprising:

receiving image data including a desired emission level for the plurality of pixels in a first row, the image data including a target value for the measurable sensor parameter.

50. A method according to claim 49, further comprising comparing the value of the measurable sensor parameter of each sensor with the image data.

51. A method according to claim 30, further comprising repeating the acts of varying, receiving, obtaining and generating for a plurality of pixels in a second row.

52. An apparatus for controlling an active matrix display including an array of pixels arranged in a plurality of rows and a plurality of columns, each pixel element including an active matrix element, the apparatus comprising:

a sensor array arranged in a plurality of rows and a plurality of columns, each sensor having a measurable sensor parameter and positioned to receive at least a portion of the radiation emitted from at least one of the pixels;

a row selector coupled to the sensor array and coupleable to the display operable to select at least one of the plurality of rows; and

a plurality of control units, each coupled to a plurality of the sensors located in a common column and a reference signal indicative of a target value of the measurable sensor parameter for a pixel in the selected row, the control unit operable to compare a measured value of the sensor parameter with the reference signal and generate a control signal, the control unit further coupled to the active matrix elements such that the active matrix elements receive the control signal and maintain the amount of radiation emitted from the light source.

53. An apparatus according to claim 52, the plurality of control units each further coupled to a reference signal indicative of the value of the measurable sensor parameter during the predetermined emission level for each of the pixels in the selected row, the control unit operable to compare the reference signal and the measured value.

54. An apparatus according to claim 52 further comprising a calibration look-up table coupled to the control units, the calibration look-up table storing at least one value of the measurable sensor parameter indicative of the predetermined emission level.

55. An apparatus according to claim 54 further comprising a line buffer coupled to the look-up table and the control units.

56. A controlled active matrix display, comprising:

an array of pixels arranged in a plurality of rows and a plurality of columns, each pixel element including an active pixel element configured to drive the pixel;

a sensor array arranged in the plurality of rows and the plurality of columns, each sensor having a measurable sensor parameter and positioned to receive at least a portion of the radiation emitted from at least one of the pixels;

a row selector coupled to the sensor array and the array of pixels and operable to select at least one of the plurality of rows;

a plurality of control units, each coupled to a plurality of the sensors located in a common column and a reference signal indicative of a target value of the measurable sensor parameter for a pixel in the selected row, the control unit operable to compare a measured value of the sensor parameter with the reference signal and generate a control signal; and

a pixel driver coupled to the active matrix elements, the pixel driver coupled to the active matrix elements and operable to vary an amount of radiation emitted from at least one pixel, the active matrix elements operable to receive the control signal and maintain the amount of radiation emitted from the pixel.

57. A controlled active matrix display according to claim 56, wherein the pixel driver provides a varying signal to the active matrix elements.

58. A controlled active matrix display according to claim 56, wherein the control units are further coupled to a reference signal indicative of a predetermined emission level, the control unit further operable to compare the measured value of the measurable sensor parameter with the reference signal to determine the predetermined emission level is attained.

59. A controlled active matrix display according to claim 56, wherein said sensor includes a photo-sensitive resistor, diode, or transistor.

60. A method of controlling light emission to a predetermined emission level in a passive matrix display having an array of pixel elements arranged in a plurality of rows and a plurality of columns, the method using a plurality of sensors having a measurable sensor parameter and a pixel driver, the method comprising:

varying light emission from a plurality of pixels in a first row using the pixel driver;

monitoring light emission from the plurality of pixels in the first row by monitoring an actual value of the measurable sensor parameter of each of a plurality of sensors, each of the plurality of sensors positioned to receive at least a portion of the light emission from one of the plurality of pixels in the first row;

coupling the actual value of the measurable sensor parameter of each of the plurality of pixels to the pixel driver; and

generating a control signal for the plurality of pixels to maintain constant emission from at the predetermined emission level.

61. A method according to claim 60, wherein each of the plurality of pixels include a light source.

62. A method according to claim 60, wherein the pixel driver provides a voltage to each of the plurality of pixels.

63. A method according to claim 60, wherein the pixel driver is not contained within any of the plurality of pixels.

64. A method according to claim 60, wherein the plurality of pixels are pixels of a liquid crystal display.

65. A method according to claim 61, wherein the light source includes a light emitting diode.

66. A method according to claim 61, wherein the light source includes a white light emitting diode.

67. A method according to claim 61, wherein the light source includes an organic light emitting diode.

68. A method according to claim 60, wherein each of the plurality of sensors include a light-sensitive resistor, optical diode, or optical transistor.

69. A method according to claim 60, wherein each of the plurality of sensors include a light-sensitive resistor and the measurable sensor parameter includes a voltage across the resistor.

70. A method according to claim 60, further comprising comparing the actual value to a reference value of the measurable sensor parameter, the reference value indicative of the predetermined emission level.

71. A method according to claim 70, wherein the reference value is an image voltage.

72. A method according to claim 70, further comprising calibrating the plurality of sensors to determine the reference value for each of the plurality of sensors.

73. A method according to claim 72, wherein the act of calibrating the sensor comprises illuminating the sensor with a calibration light source.

74. A method according to claim 61, wherein the light source is an organic light emitting diode and the act of generating a control signal includes increasing a current through the light emitting diode.

75. A method according to claim 60, wherein the act of comparing the measured value with the reference value includes coupling the measured value and the predetermined value to a comparator.

76. A method according to claim 60, wherein the pixel driver provides a varying signal to each of the plurality of pixels in the first row to cause increasing light emission from the pixel and wherein the act of generating a control signal comprises replacing the varying signal with a constant signal to cause stable light emission from each of the plurality of pixels in the first row.

77. A method according to claim 76, wherein the varying signal comprises a ramp signal.

78. A method according to claim 77, wherein the ramp signal comprises a voltage ramp.

79. A method according to claim 60, further comprising repeating the acts of varying, monitoring, coupling and generating for a plurality of light sources in a second row.

80. An apparatus for controlling a passive matrix display including an array of pixels arranged in a plurality of rows and a plurality of columns, the apparatus comprising:

a sensor array arranged in a plurality of rows and a plurality of columns, each sensor having a measurable sensor parameter and positioned to receive at least a portion of the radiation emitted from at least one of the pixels;

a row selector coupled to the sensor array and coupleable to the display operable to select at least one of the plurality of rows;

a plurality of comparators, each coupled to a plurality of the sensors located in a common column and a reference signal indicative of a target value of the measurable sensor parameter for a pixel in the selected row, the comparator operable to compare a measured value of the sensor parameter with the reference signal and generate a control signal; and

a plurality of pixel drivers, each coupled to pixels located in a common column, each of the plurality of pixel rivers coupled to a selected one of the plurality of comparators and operable to receive the control signal and maintain the amount of radiation emitted from the pixels.

81. An apparatus according to claim 80 further comprising a calibration look-up table coupled to at least one of the plurality of comparators, the calibration look-up table storing at least one value of the measurable sensor parameter indicative of the predetermined emission level.

82. A controlled passive matrix display comprising:

an array of pixels arranged in a plurality of rows and a plurality of columns;

a sensor array arranged in a plurality of rows and a plurality of columns, each sensor having a measurable sensor parameter and positioned to receive at least a portion of the radiation emitted from at least one of the pixels;

a row selector coupled to the sensor array and the array of light sources and operable to select at least one of the plurality of rows;

a plurality of comparators, each coupled to a plurality of the sensors located in a common column and a reference signal indicative of a target value of the measurable sensor parameter for a pixel in the selected row, the comparator operable to compare a measured value of the sensor parameter with the reference signal and generate a control signal; and

a plurality of pixel drivers coupled to the plurality of comparators, each pixel driver further coupled to the pixels in a common column, the pixel drivers operable to vary the amount of light emitted from the light source and, responsive to the control signal, to maintain the amount of light emitted from the pixel.

83. A controlled passive matrix display according to claim 82 wherein the pixel driver provides a varying signal to the pixels.

84. A controlled pixel system according to claim 82, the comparator further operable to compare the measured value of the measurable sensor parameter with the reference signal to determine the predetermined emission level is attained.

85. A controlled pixel system according to claim 82 wherein said sensor array includes a photo-sensitive resistor, diode, or transistor.

86. A method for aligning a dark shield with a sensor and a plurality of contacts, the method comprising:

forming the dark shield on a first surface of a transparent substrate having a second surface opposite the first surface;

depositing an insulating material over the dark shield;

depositing material for the sensor over the insulating material and the dark shield;

depositing material for the electrical contacts over the material for the sensor;

coating the substrate with negative photoresist above the material for the electrical contacts;

exposing the negative photoresist with a light source positioned to pass light through the transparent substrate, such that a portion of the light is blocked by the dark shield;

developing the negative photoresist; and

etching the material for the electrical contacts through the developed negative photoresist, such that a plurality of electrical contacts are formed over the material for the sensor, and the plurality of electrical contacts are aligned with the dark shield.

87. A method for aligning a dark shield with a sensor and a plurality of contacts, the method comprising:

forming the dark shield on a first surface of a transparent substrate having a second surface opposite the first surface;

depositing an insulating material over the dark shield;

depositing material for the sensor over the insulating material and the dark shield;

coating the substrate with positive photoresist above the sensor material;

exposing the positive photoresist with a light source positioned to pass light through the transparent substrate, such that a portion of the light is blocked by the dark shield;

developing the positive photoresist;

etching the sensor material to conform to the dark shield;

depositing contact metal over the sensor material; and

etching contact metal such that a plurality of electrical contacts are formed over and aligned to the material for the plurality of sensors.