Light emitting device and electronic apparatus using the same
View Patent ↗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 image 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 current supply to the target pixel is corrected for achieving a desired luminance. The other pixels than the target pixel are supplied with an excessive current and hence, the individual gradation levels of the pixels are lowered by correcting the image signal for driving the pixel with the deteriorated light emitting element on as-needed basis, the correction of the image 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.
1. A light emitting device comprising:
a plural light emitting elements;
a current source for supplying a current to the plural light emitting elements;
means for calculating an accumulation of light emission periods or gradation levels of each of the plural light emitting elements based on an image signal for controlling the light emission periods of the plural light emitting elements;
means for storing data on a time-varying luminance characteristic of a light emitting element;
means for determining an amount of luminance variation of the plural light emitting elements based on the calculated accumulation of the light emission periods or gradation levels of the plural light emitting elements and on the data on the time-varying luminance characteristic of the light emitting element, and for correcting the current supplied from the current source to the plural light emitting elements so that the luminance of one particular light emitting element among the plural light emitting elements returns to an initial value; and
means for correcting the image signal so that a difference between an amount of luminance variation of the one particular light emitting element and that of the other light emitting elements are compensated, and for correcting the gradation level of the other light emitting elements.
2. A light emitting device according to claim 1 , wherein the correction of the current supplied from the current 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 value reaches a given value.
3. An electronic apparatus comprising the light emitting device according to claim 1 , wherein the electronic apparatus is 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.
4. A light emitting device comprising:
a plural light emitting elements;
a current source for supplying a current to the plural light emitting elements;
means for calculating an accumulation of light emission periods or gradation levels of each of the plural light emitting elements based on an image signal for controlling the light emission periods of the plural light emitting elements;
means for storing data on a time-varying luminance characteristic of a light emitting element;
means for determining an amount of luminance variation of the plural light emitting elements based on the calculated accumulation of the light emission periods or gradation levels of the plural light emitting elements and on the data on the time-varying luminance characteristic of the light emitting element, and for correcting the current supplied from the current source to the plural light emitting elements so that the luminance of one particular light emitting element among the plural light emitting elements returns to an initial value; and
means for correcting the image signal so that a difference between an amount of luminance variation of the one particular light emitting element and that of the other light emitting elements are compensated, and for correcting the gradation level of the other light emitting elements,
wherein an image signal for controlling the gradation level of the other light emitting elements is increased by m bits (m denotes an integer) than the one particular light emitting element by the correction of the image signal.
5. A light emitting device according to claim 4 , wherein the correction of the current supplied from the current 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 value reaches a given value.
6. An electronic apparatus comprising the light emitting device according to claim 4 , wherein the electronic apparatus is 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.
7. A light emitting device comprising:
a plural light emitting elements;
a current source for supplying a current to the plural light emitting elements;
means for sampling an image signal for controlling light emission periods of the plural light emitting elements over several times, for detecting a presence or absence of light emissions from each of the plural light emitting elements, and for counting the number of light emissions of each of the plural light emitting elements;
means for storing data on a time-varying luminance characteristic of a light emitting element;
means for determining an amount of luminance variation of each of the plural light emitting elements based on a ratio of the number of light emissions from each of the plural light emitting elements versus the total count of detections and on the data on the time-varying luminance characteristic of the light emitting element, and for correcting the current supplied from the current source to the plural light emitting elements so that the luminance of one particular light emitting element among the plural light emitting elements returns to an initial value; and
means for correcting the image signal so that a difference between an amount of luminance variation of the one particular light emitting element and that of the other light emitting elements are compensated, and for correcting the gradation level of each of the other light emitting elements.
8. A light emitting device according to claim 7 , wherein the correction of the current supplied from the current 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 value reaches a given value.
9. An electronic apparatus comprising the light emitting device according to claim 7 , wherein the electronic apparatus is 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.
10. A light emitting device comprising:
a plural light emitting elements;
a current source for supplying a current to the plural light emitting elements;
means for sampling an image signal for controlling light emission periods of the plural light emitting elements over several times, for detecting a presence or absence of light emissions from each of the plural light emitting elements, and for counting the number of light emissions of each of the plural light emitting elements;
means for storing data on a time-varying luminance characteristic of a light emitting element;
means for determining an amount of luminance variation of each of the plural light emitting elements based on a ratio of the number of light emissions from each of the plural light emitting elements versus the total count of detections and on the data on the time-varying luminance characteristic of the light emitting element, and for correcting the current supplied from the current source to the plural light emitting elements so that the luminance of one particular light emitting element among the plural light emitting elements returns to an initial value; and
means for correcting the image signal so that a difference between an amount of luminance variation of the one particular light emitting element and that of the other light emitting elements are compensated, and for correcting the gradation level of each of the other light emitting elements,
wherein an image signal for controlling the gradation level of the another light emitting elements is increased by m bits (m denotes an integer) than the one light emitting element by the correction of the image signal.
11. A light emitting device according to claim 10 , wherein the correction of the current supplied from the current 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 value reaches a given value.
12. An electronic apparatus comprising the light emitting device according to claim 10 , wherein the electronic apparatus is 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.
13. A light emitting device comprising:
a plural first light emitting elements;
a current source for supplying a current to the plural first light emitting elements;
means for calculating a sum of light emission periods of each of the plural first light emitting elements based on image signals;
means for storing an amount of luminance variation of a second light emitting element based on a sum of light emission periods thereof;
means for determining an amount of luminance variation of each of the plural first light emitting elements from the sum of the light emission periods of each of the plural first light emitting elements and the stored amount of luminance variation of the second light emitting element based on the sum of the light emission periods thereof, for detecting one particular first light emitting element having the greatest sum of the light emission period from the plural first light emitting elements, and for correcting the current supply from the current source to the plural first light emitting elements based on the amount of luminance variation of the one particular first light emitting element so that the luminance of one particular first light emitting elements returns to an initial value; and
means for correcting the image signal so that a difference between an amount of luminance variation of the one particular first light emitting element and that of the other first light emitting elements are compensated, and for correcting the gradation level of the other first light emitting elements.
14. A light emitting device according to claim 13 , wherein the storage means comprises a static memory circuit.
15. A light emitting device according to claim 13 , wherein the storage means comprises a dynamic memory circuit.
16. A light emitting device according to claim 13 , wherein the storage means comprises a ferroelectric memory circuit.
17. A light emitting device according to claim 13 , wherein the correction of the current supplied from the current 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 value reaches a given value.
18. An electronic apparatus comprising the light emitting device according to claim 13 , wherein the electronic apparatus is 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.
19. a plural first light emitting elements;
a current source for supplying a current to the plural first light emitting elements;
means for calculating a sum of light emission periods of each of the plural first light emitting elements based on image signals;
means for storing an amount of luminance variation of a second light emitting element based on a sum of light emission periods thereof;
means for determining an amount of luminance variation of each of the plural first light emitting elements from the sum of the light emission periods of each of the plural first light emitting elements and the stored amount of luminance variation of the second light emitting element based on the sum of the light emission periods thereof, for detecting one particular first light emitting element having the greatest sum of the light emission period from the plural first light emitting elements, and for correcting the current supply from the current source to the plural first light emitting elements based on the amount of luminance variation of the one particular first light emitting element so that the luminance of one particular first light emitting elements returns to an initial value; and
means for correcting the image signal so that a difference between an amount of luminance variation of the one particular first light emitting element and that of the other first light emitting elements are compensated, and for correcting the gradation level of the other first light emitting elements,
wherein an image signal for controlling the gradation level of the another light emitting elements is increased by m bits (m denotes an integer) than the one light emitting element by the correction of the image signal.
20. A light emitting device according to claim 19 , wherein the storage means comprises a static memory circuit.
21. A light emitting device according to claim 19 , wherein the storage means comprises a dynamic memory circuit.
22. A light emitting device according to claim 19 , wherein the storage means comprises a ferroelectric memory circuit.
23. A light emitting device according to claim 19 , wherein the correction of the current supplied from the current 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 value reaches a given value.
24. An electronic apparatus comprising the light emitting device according to claim 19 , wherein the electronic apparatus is 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.
25. A light emitting device comprising:
a plural light emitting elements;
a current source for supplying a current to the plural light emitting elements;
a first circuit for calculating an accumulation of light emission periods or gradation levels of each of the plural light emitting elements based on an image signal;
a second circuit for storing data on a time-varying luminance characteristic of a light emitting element;
a third circuit for correcting the current supplied from the current source to the plural light emitting elements based on an amount of luminance variation of the plural light emitting elements or gradation levels of the plural light emitting elements and on the data on the time-varying luminance characteristic of the light emitting element; and
a fourth circuit for correcting the image signal in order to correct the gradation level of at least a part of the plural light emitting elements.
26. An electronic apparatus comprising the light emitting device according to claim 25 , wherein the electronic apparatus is 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.
27. A light emitting device comprising:
a plural light emitting elements;
a current source for supplying a current to the plural light emitting elements;
a first circuit for detecting a presence or absence of light emissions from each of the plural light emitting elements by sampling an image signal over several times;
a second circuit for counting the number of light emissions of the each of the plural light emitting elements;
a third circuit for storing data on a time-varying luminance characteristic of a light emitting element;
a fourth circuit for correcting the current supplied from the current source to the plural light emitting elements based on a ratio of the number of light emissions versus the total defection and on the data on the time-varying luminance characteristic of the light emitting element; and
a fifth circuit for correcting the image signal in order to correct the gradation level of at least a part of the plural light emitting elements.
28. An electronic apparatus comprising the light emitting device according to claim 27 , wherein the electronic apparatus is 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.
29. A light emitting device comprising:
a plural first light emitting elements;
a current source for supplying a current to the plural first light emitting elements;
a first circuit for calculating a sum of light emission periods of each of the plural first light emitting elements based on image signals;
a second circuit for storing an amount of luminance variation of a second light emitting element based on a sum of light emission periods thereof;
a third circuit for correcting the current supplied from the current source to the plural first light emitting elements from the sum of the light emission periods of each of the plural first light emitting elements and the amount of luminance variation of a second light emitting element based on a sum of light emission periods thereof;
a fourth circuit for correcting the image signal in order to correcting the gradation level of at least a part of the plural first light emitting elements.
30. A light emitting device according to claim 29 , wherein the storage means comprises a static memory circuit.
31. A light emitting device according to claim 29 , wherein the storage means comprises a dynamic memory circuit.
32. A light emitting device according to claim 29 , wherein the storage means comprises a ferroelectric memory circuit.
33. An electronic apparatus comprising the light emitting device according to claim 29 , wherein the electronic apparatus is 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.
34. A light emitting device comprising:
a plural light emitting elements;
a current source for supplying a current to the plural light emitting elements;
a counter;
a circuit for storing the data on a time-varying luminance characteristic of a light emitting element;
a first correction circuit for correcting the current supplied from the current source to the plural light emitting elements, the first correction circuit connected to the current source; and
a second correction circuit for correcting for correcting the image, the second correction circuit connected to the counter,
wherein the circuit for storing the data is connected to the first correction circuit and the second correction circuit, respectively.
35. An electronic apparatus comprising the light emitting device according to claim 34 , wherein the electronic apparatus is 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.