Light emitting device and electronic apparatus using the same

• US 20030071804A1
• Filed: 09/27/2002
• Published: 04/17/2003
• Est. Priority Date: 09/28/2001
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun, Yamazaki, Shunpei
• Granted Patent: US 7,158,157 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• 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 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/048 using evaluation of the usage time
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/2022 using sub-frames
• 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

Abstract

Providing a light emitting device capable of suppressing the variations of luminance of OLEDs associated with the deterioration of an organic light emitting material, and achieving a consistent luminance. An input video signal is constantly or periodically sampled to sense a light emission period or displayed gradation level of each of light emitting elements of pixels and then, a pixel suffering the greatest deterioration and decreased luminance is predicted from the accumulations of the sensed values. A voltage supply to the target pixel is corrected for achieving a desired luminance. The other pixels than the target pixel are supplied with an excessive voltage and hence, the individual gradation levels of the pixels are lowered by correcting the video signal for driving the pixel with the deteriorated light emitting element on as-needed basis, the correction of the video signal made by comparing the accumulation of the sensed values of each of the other pixels with a previously stored data on a time-varying luminance characteristic of the light emitting element.

Claims

1. A light emitting device comprising:

a plurality of light emitting elements;

a voltage source for supplying a voltage to the plural light emitting elements;

means for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

means for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

means for storing data on a time-varying luminance characteristic of the light emitting element;

means for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels;

means for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

means for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element.

11. A light emitting device as claimed in claim 1,

wherein the means for storing the calculated accumulation comprises at least a volatile memory and a non-volatile memory.

17. A light emitting device as claimed in claim 1,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a static memory circuit (SRAM).

23. A light emitting device as claimed in claim 1,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a dynamic memory circuit (DRAM).

29. A light emitting device as claimed in claim 1,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a ferroelectric memory circuit (FRAM).

35. A light emitting device as claimed in claim 1, wherein the correction of the voltage supplied from the voltage source to the plural light emitting elements is suspended when a ratio of the amount of luminance variation of the one particular light emitting element versus the initial luminance reaches a given value.

41. An electronic apparatus selected from the group consisting of a display device, a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction device, a goggle type display, a video camera and a mobile phone comprising the light emitting device as claimed in claim 1.

47. A light emitting device as claimed in claim 1,

wherein the accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels of said one of the plural light emitting elements is maximum of those of the plural light emitting elements.

53. A light emitting device as claimed in claim 1,

wherein the accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels of said one of the plural light emitting elements is maximum of those of the plural light emitting elements.

2. A light emitting device comprising:

a plurality of light emitting elements;

a voltage source for supplying a voltage to the plural light emitting elements;

means for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

means for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

means for storing data on a time-varying luminance characteristic of the light emitting element;

means for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels;

means for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

means for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element,

wherein the correction of the video signal provides a video signal increased by m bits (m denotes an integer) for controlling the gradation level of each of the other light emitting elements than the one particular light emitting element.

12. A light emitting device as claimed in claim 2,

wherein the means for storing the calculated accumulation comprises at least a volatile memory and a non-volatile memory.

18. A light emitting device as claimed in claim 2,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a static memory circuit (SRAM).

24. A light emitting device as claimed in claim 2,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a dynamic memory circuit (DRAM).

30. A light emitting device as claimed in claim 2,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a ferroelectric memory circuit (FRAM).

36. A light emitting device as claimed in claim 2, wherein the correction of the voltage supplied from the voltage source to the plural light emitting elements is suspended when a ratio of the amount of luminance variation of the one particular light emitting element versus the initial luminance reaches a given value.

42. An electronic apparatus selected from the group consisting of a display device, a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction device, a goggle type display, a video camera and a mobile phone comprising the light emitting device as claimed in claim 2.

48. A light emitting device as claimed in claim 2,

wherein the accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels of said one of the plural light emitting elements is maximum of those of the plural light emitting elements.

54. A light emitting device as claimed in claim 2,

wherein the accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels of said one of the plural light emitting elements is minimum of those of the plural light emitting elements.

3. A light emitting device comprising:

a plurality of light emitting elements;

a voltage source for supplying a voltage to the plural light emitting elements;

means for sampling a video signal for controlling light emission periods and gradation levels of the plural light emitting elements over several times;

means for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

means for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

means for storing data on a time-varying luminance characteristic of the light emitting element;

means for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and gradation levels;

means for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

means for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element.

13. A light emitting device as claimed in claim 3,

wherein the means for storing the calculated accumulation comprises at least a volatile memory and a non-volatile memory.

19. A light emitting device as claimed in claim 3,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a static memory circuit (SRAM).

25. A light emitting device as claimed in claim 3,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a dynamic memory circuit (DRAM).

31. A light emitting device as claimed in claim 3,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a ferroelectric memory circuit (FRAM).

37. A light emitting device as claimed in claim 3, wherein the correction of the voltage supplied from the voltage source to the plural light emitting elements is suspended when a ratio of the amount of luminance variation of the one particular light emitting element versus the initial luminance reaches a given value.

43. An electronic apparatus selected from the group consisting of a display device, a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction device, a goggle type display, a video camera and a mobile phone comprising the light emitting device as claimed in claim 3.

49. A light emitting device as claimed in claim 3,

wherein the accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels of said one of the plural light emitting elements is maximum of those of the plural light emitting elements.

55. A light emitting device as claimed in claim 3,

wherein the accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels of said one of the plural light emitting elements is minimum of those of the plural light emitting elements.

4. A light emitting device comprising:

a plurality of light emitting elements;

a voltage source for supplying a voltage to the plural light emitting elements;

means for sampling a video signal for controlling light emission periods and gradation levels of the plural light emitting elements over several times;

means for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

means for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

means for storing data on a time-varying luminance characteristic of the light emitting element;

means for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and gradation levels;

means for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

means for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element,

wherein the correction of the video signal provides a video signal increased by m bits (m denotes an integer) for controlling the gradation level of each of the other light emitting elements than the one particular light emitting element.

14. A light emitting device as claimed in claim 4,

wherein the means for storing the calculated accumulation comprises at least a volatile memory and a non-volatile memory.

20. A light emitting device as claimed in claim 4,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a static memory circuit (SRAM).

26. A light emitting device as claimed in claim 4,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a dynamic memory circuit (DRAM).

32. A light emitting device as claimed in claim 4,

wherein the means for storing data on a time-varying luminance characteristic of the light emitting element comprises a ferroelectric memory circuit (FRAM).

38. A light emitting device as claimed in claim 4, wherein the correction of the voltage supplied from the voltage source to the plural light emitting elements is suspended when a ratio of the amount of luminance variation of the one particular light emitting element versus the initial luminance reaches a given value.

44. An electronic apparatus selected from the group consisting of a display device, a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction device, a goggle type display, a video camera and a mobile phone comprising the light emitting device as claimed in claim 4.

50. A light emitting device as claimed in claim 4,

wherein the accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels of said one of the plural light emitting elements is maximum of those of the plural light emitting elements.

56. A light emitting device as claimed in claim 4,

wherein the accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels of said one of the plural light emitting elements is minimum of those of the plural light emitting elements.

5. A light emitting device comprising:

a plurality of first light emitting elements;

a voltage source for supplying a voltage to the plural first light emitting elements;

means for calculating a sum of one selected from the group consisting of light emission periods and gradation levels of each of the plural first light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

means for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

means for storing an amount of luminance variation of a second light emitting element based on a sum of at least one selected from the group consisting of light emission periods and gradation levels thereof;

means for determining an amount of luminance variation of each of the plural first light emitting elements based on the sum of the at least one selected from the group consisting of the light emission periods and the gradation levels of each of the plural first light emitting elements and on the stored amount of luminance variation of the second light emitting element with respect to the sum of the light emission periods thereof, and for determining one particular first light emitting element from the plural first light emitting elements based on the sum of the at least one selected from the group consisting of the light emission periods and the gradation levels;

means for correcting the voltage supplied from the voltage source to the plural first light emitting elements based on the amount of luminance variation of the one particular first light emitting element thereby returning the luminance of the one particular first light emitting element to an initial luminance; and

means for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular first light emitting element and an amount of luminance variation of each of the other first light emitting elements, thereby correcting the gradation level of each of the other first light emitting elements than the one particular light emitting element.

15. A light emitting device as claimed in claim 5,

wherein the means for storing the calculated accumulation comprises at least a volatile memory and a non-volatile memory.

21. A light emitting device as claimed in claim 5,

wherein the means for storing an amount of luminance variation of a second light emitting element comprises a static memory circuit (SRAM).

27. A light emitting device as claimed in claim 5,

wherein the means for storing an amount of luminance variation of a second light emitting element comprises a dynamic memory circuit (DRAM).

33. A light emitting device as claimed in claim 5,

wherein the means for storing an amount of luminance variation of a second light emitting element comprises a ferroelectric memory circuit (FRAM).

39. A light emitting device as claimed in claim 5, wherein the correction of the voltage supplied from the voltage source to the plural light emitting elements is suspended when a ratio of the amount of luminance variation of the one particular light emitting element versus the initial luminance reaches a given value.

45. An electronic apparatus selected from the group consisting of a display device, a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction device, a goggle type display, a video camera and a mobile phone comprising the light emitting device as claimed in claim 5.

51. A light emitting device as claimed in claim 5,

wherein the sum of at least one selected from the group consisting of the light emission periods and the gradation levels of said one of the plural light emitting elements is maximum of those of the plural light emitting elements.

57. A light emitting device as claimed in claim 5,

wherein the sum of at least one selected from the group consisting of the light emission periods and the gradation levels of said one of the plural light emitting elements is minimum of those of the plural light emitting elements.

6. A light emitting device comprising:

a plurality of first light emitting elements;

a voltage source for supplying a voltage to the plurality of first light emitting elements;

means for calculating a sum of one selected from the group consisting of light emission periods and gradation levels of each of the plural first light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

means for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

means for storing an amount of luminance variation of a second light emitting element based on a sum of at least one selected from the group consisting of light emission periods and gradation levels thereof;

means for determining an amount of luminance variation of each of the plural first light emitting elements based on the sum of the at least one selected from the group consisting of the light emission periods and the gradation levels of each of the plural first light emitting elements and on the stored amount of luminance variation of the second light emitting element with respect to the sum of the light emission periods thereof, and for determining one particular first light emitting element from the plural first light emitting elements based on the sum of the at least one selected from the group consisting of the light emission periods and the gradation levels;

means for correcting the voltage supplied from the voltage source to the plural first light emitting elements based on the amount of luminance variation of the one particular first light emitting element thereby returning the luminance of the one particular first light emitting element to an initial luminance; and

means for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular first light emitting element and an amount of luminance variation of each of the other first light emitting elements, thereby correcting the gradation level of each of the other first light emitting elements than the one particular light emitting element,

wherein the correction of the video signal provides a video signal increased by m bits (m denotes an integer) for controlling the gradation level of each of the other light emitting elements than the one particular light emitting element.

16. A light emitting device as claimed in claim 6,

wherein the means for storing the calculated accumulation comprises at least a volatile memory and a non-volatile memory.

22. A light emitting device as claimed in claim 6,

wherein the means for storing an amount of luminance variation of a second light emitting element comprises a static memory circuit (SRAM).

28. A light emitting device as claimed in claim 6,

wherein the means for storing an amount of luminance variation of a second light emitting element comprises a dynamic memory circuit (DRAM).

34. A light emitting device as claimed in claim 6,

wherein the means for storing an amount of luminance variation of a second light emitting element comprises a ferroelectric memory circuit (FRAM).

40. A light emitting device as claimed in claim 6, wherein the correction of the voltage supplied from the voltage source to the plural light emitting elements is suspended when a ratio of the amount of luminance variation of the one particular light emitting element versus the initial luminance reaches a given value.

46. An electronic apparatus selected from the group consisting of a display device, a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction device, a goggle type display, a video camera and a mobile phone comprising the light emitting device as claimed in claim 6.

52. A light emitting device as claimed in claim 6,

wherein the sum of at least one selected from the group consisting of the light emission periods and gradation levels of said one of the plural light emitting elements is maximum of those of the plural light emitting elements.

58. A light emitting device as claimed in claim 6,

wherein the sum of at least one selected from the group consisting of the light emission periods and the gradation levels of said one of the plural light emitting elements is minimum of those of the plural light emitting elements.

7. A light emitting device comprising:

a plurality of light emitting elements;

a voltage source for supplying a voltage to the plural light emitting elements;

a counter portion for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

a memory circuit portion for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

a correction data storage portion for storing data on a time-varying luminance characteristic of the light emitting element;

an arithmetic circuit for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels;

a voltage correction circuit for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

a video signal correction circuit for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element.

8. A light emitting device comprising:

a plurality of light emitting elements;

a voltage source for supplying a voltage to the plural light emitting elements;

a counter portion for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

a memory circuit portion for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

a correction data storage portion for storing data on a time-varying luminance characteristic of the light emitting element;

an arithmetic circuit for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels;

a voltage correction circuit for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

a video signal correction circuit for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element,

wherein the correction of the video signal provides a video signal increased by m bits (m denotes an integer) for controlling the gradation level of each of the other light emitting elements than the one particular light emitting element.

9. A light emitting device comprising:

a plurality of light emitting elements;

a voltage source for supplying a voltage to the plural light emitting elements;

a sampling circuit for sampling a video signal for controlling light emission periods and gradation levels of the plural light emitting elements over several times;

a counter portion for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

a memory circuit portion for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

a correction data storage portion for storing data on a time-varying luminance characteristic of the light emitting element;

an arithmetic circuit for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels;

a voltage correction circuit for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

a video signal correction circuit for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element.

10. A light emitting device comprising:

a plurality of light emitting elements;

a voltage source for supplying a voltage to the plural light emitting elements;

a sampling circuit for sampling a video signal for controlling light emission periods and gradation levels of the plural light emitting elements over several times;

a counter portion for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

a memory circuit portion for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

a correction data storage portion for storing data on a time-varying luminance characteristic of the light emitting element;

an arithmetic circuit for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels;

a voltage correction circuit for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

a video signal correction circuit for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element,

wherein the correction of the video signal provides a video signal increased by m bits (m denotes an integer) for controlling the gradation level of each of the other light emitting elements than the one particular light emitting element.

59. A light emitting device comprising:

a substrate on the substrate;

a pixel portion on the substrate comprising a plurality of light emitting elements;

a signal line drive circuit on the substrate;

a scanning line drive circuit on the substrate;

a flexible printed circuit on the substrate;

a voltage source on the substrate for supplying a voltage to the plural light emitting elements;

means for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

means for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

means for storing data on a time-varying luminance characteristic of the light emitting element;

means for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels;

means for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

means for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element

wherein all of the means are on the substrate.

60. A light emitting device comprising:

a substrate on the substrate;

a pixel portion on the substrate comprising a plurality of light emitting elements;

a signal line drive circuit on the substrate;

a scanning line drive circuit on the substrate;

a flexible printed circuit on the substrate;

a voltage source on the substrate for supplying a voltage to the plural light emitting elements;

means for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

means for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

means for storing data on a time-varying luminance characteristic of the light emitting element;

means for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and the gradation levels;

means for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

means for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element,

wherein all of the means are on the substrate, and

wherein the correction of the video signal provides a video signal increased by m bits (m denotes an integer) for controlling the gradation level of each of the other light emitting elements than the one particular light emitting element.

61. A light emitting device comprising:

a substrate on the substrate;

a pixel portion on the substrate comprising a plurality of light emitting elements;

a signal line drive circuit on the substrate;

a scanning line drive circuit on the substrate;

a flexible printed circuit on the substrate;

a voltage source on the substrate for supplying a voltage to the plural light emitting elements;

means for sampling a video signal for controlling light emission periods and gradation levels of the plural light emitting elements over several times;

means for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

means for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

means for storing data on a time-varying luminance characteristic of the light emitting element;

means for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and gradation levels;

means for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

means for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element,

wherein all of the means are on the substrate.

62. A light emitting device comprising:

a substrate on the substrate;

a pixel portion on the substrate comprising a plurality of light emitting elements;

a signal line drive circuit on the substrate;

a scanning line drive circuit on the substrate;

a flexible printed circuit on the substrate;

a voltage source on the substrate for supplying a voltage to the plural light emitting elements;

means for sampling a video signal for controlling light emission periods and gradation levels of the plural light emitting elements over several times;

means for calculating an accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements based on video signals for controlling the light emission periods of the plural light emitting elements;

means for storing the calculated accumulation of at least one selected from the group consisting of light emission periods and gradation levels of each of the plural light emitting elements;

means for storing data on a time-varying luminance characteristic of the light emitting element;

means for determining an amount of luminance variation of each of the plural pixels based on the data on the time-varying luminance characteristic of the light emitting element and the calculated accumulation of at least one selected from the group consisting of the light emission periods and gradation levels;

means for correcting the voltage supplied from the voltage source to the plural light emitting elements to return the luminance of one of the plural light emitting elements to an initial luminance; and

means for correcting the video signal in a manner to compensate for a difference between the amount of luminance variation of the one particular light emitting element and an amount of luminance variation of each of the other light emitting elements than the one particular light emitting element, thereby correcting the gradation level of each of the other light emitting elements than the one particular light emitting element,

wherein all of the means are on the substrate, and

wherein the correction of the video signal provides a video signal increased by m bits (m denotes an integer) for controlling the gradation level of each of the other light emitting elements than the one particular light emitting element.