Flat-panel display with luminance feedback

• US 20040032382A1
• Filed: 08/12/2003
• Published: 02/19/2004
• Est. Priority Date: 09/29/2000
• Status: Active Grant

• Current Assignee: Global OLED Technology LLC (LG Display Co., Ltd.)
• Original Assignee: Ching W. Tang, Ronald S. Cok
• Inventors: Cok, Ronald S., Tang, Ching W.
• Granted Patent: US 7,064,733 B2
• Time in Patent Office: Days
• US Class Current: 345/82
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• 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 2320/045 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 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 2360/148 the light being detected by light detection means within each pixel
• CPC Class Codes: G09G 3/3216 using a passive matrix
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: H10K 59/13 comprising photosensors that control luminance
• CPC Class Codes: H10K 59/17 Passive-matrix OLED displays

Abstract

An image display, includes a substrate; a light emitter formed on the substrate; and a photo-sensor formed on the substrate and optically coupled directly to the light emitter.

Claims

1. An image display, comprising:

a) a substrate;

b) an array of addressable light emitters formed on the substrate;

c) a drive circuit for driving the light emitters to emit light in an imagewise pattern;

d) one or more photo-sensors formed on the substrate and directly optically coupled to the light emitters in the array to detect light emitted by the light emitters and to generate a feedback signal in response thereto; and

e) a feedback control circuit responsive to the feedback signal for controlling the drive circuit to control the desired light output for each brightness level of the display.

2. The image display claimed in claim 1 wherein the substrate is transparent and the light emitters emit light through the transparent substrate.

3. The image display claimed in claim 1 wherein a transparent cover encapsulates the image display and the light emitters emit light through the transparent cover.

4. The image display claimed in claim 1 wherein the photo-sensors are organic photo-conductors.

5. The image display claimed in claim 1 wherein the photo-sensors are made of silicon materials.

6. The image display claimed in claim 1 wherein the light emitters are organic light emitting diodes.

7. The image display claimed in claim 1 wherein the light emitters are optically transparent.

8. The image display claimed in claim 1 wherein the photo-sensors are optically transparent.

9. The image display claimed in claim 1 wherein the array of light emitters and the one or more photo-sensors are arranged adjacent to each other on the substrate.

10. The image display claimed in claim 1 wherein the light emitters are disposed between one or more photo-sensors and the substrate.

11. The image display claimed in claim 1 wherein one or more photo-sensors are disposed between the light emitters and the substrate.

12. The image display claimed in claim 1 wherein the one or more photo-sensors are separated from the light emitters by an optically transparent material.

13. The image display claimed in claim 12 wherein the optically transparent material is electrically insulating.

14. The image display claimed in claim 12 wherein the optically transparent material is electrically conductive.

15. The image display claimed in claim 1 wherein the feedback control circuit compares the feedback signal to a reference signal to produce a modified signal value that is supplied to the drive circuit to modify the output of the light emitters.

16. The image display claimed in claim 15 wherein a separate reference signal is used for each of the different brightness levels produced by the light emitter.

17. The image display claimed in claim 15 wherein the light emitters include emitters that emit different colors of light and wherein a separate reference signal is used for each of the different colored light emitters.

18. The image display claimed in claim 15 wherein the feedback control circuit generates a single feedback signal and wherein the drive circuit modifies a voltage used to power the light emitters in response to the feedback signal.

19. The image display claimed in claim 15 wherein the feedback control circuit generates a separate feedback control signal for each light emitter.

20. The image display claimed in claim 15 wherein the feedback control circuit is integrated on the substrate.

21. The image display claimed in claim 15 wherein the drive control circuit includes a lookup table containing the modified signal values.

22. The image display claimed in claim 21 wherein the light emitters include emitters that emit different colors of light and wherein the drive control circuit contains a lookup table for each of the colors.

23. The image display claimed in claim 21 wherein the light emitters include emitters that emit different brightnesses and wherein the lookup table contains a signal value for each of the brightnesses.

24. The image display claimed in claim 15 wherein the display further comprises means for compensating for ambient light that reaches the photosensor(s).

25. The image display claimed in claim 21 wherein the drive control circuit further comprises means for periodically updating the lookup table.

26. The image display claimed in claim 21 wherein the feedback control circuit modifies the signal values in the lookup table.

27. The image display claimed in claim 1 wherein the display includes a single photosensor that detects light emitted by any of the light emitters.

28. The image display claimed in claim 1 wherein the display includes a plurality of photo-sensors each of which is arranged to detect light emitted by a separate group of light emitters.

29. The image display claimed in claim 1 wherein the display includes one photo-sensor for each light emitter arranged to detect light from the light emitter.

30. The image display claimed in claim 1 wherein the one or more photo-sensors are formed on the substrate.

31. The image display claimed in claim 1 wherein:

a) the light emitters comprise, in order;

i) an electrode layer on the substrate;

ii) an electro-luminescent layer; and

iii) a second electrode layer;

and

b) wherein the photo-sensor comprises, in order;

i) a photo-sensor layer; and

ii) a third electrically conductive layer.

32. The image display claimed in claim 31 further comprising a fourth electrode layer between the second layer and the photo-sensor layer.

33. The image display claimed in claim 32 further comprising an electrically insulating layer located between the second and the fourth electrode layers.

34. The image display claimed in claim 31 wherein any of the electrode layers are optically transparent.

35. The image display claimed in claim 1 wherein:

a) the photo-sensor comprises, in order;

i) a first electrode layer on the substrate;

ii) a photo-sensor layer; and

iii) a second electrically conductive layer;

and wherein

b) the light emitters comprise, in order;

i) an electro-luminescent layer; and

ii) a third electrode layer.

36. The image display claimed in claim 35 further comprising a fourth electrode layer between the second layer and the electro-luminescent layer.

37. The image display claimed in claim 36 further comprising an electrically insulating layer located between the second and the fourth electrode layers.

38. The image display claimed in claim 35 wherein any of the electrode layers are optically transparent.

39. The image display claimed in claim 1 wherein the display is an active matrix display.

40. The image display claimed in claim 1 wherein the display is a passive matrix display.

41. The image display claimed in claim 1 wherein the feedback control circuit compares the feedback signal to a model of light emitter behavior.

42. The image display claimed in claim 1 wherein the feedback control circuit compares the feedback signal to empirical data relating to the performance of an exemplary display.

43. The image display claimed in claim 1 wherein the feedback control circuit compares the feedback signal to historical light emitter attribute data.

44. The image display claimed in claim 1 wherein the display includes a plurality of photo-sensors each of which is individually addressable.

45. The image display claimed in claim 1, wherein the feedback signal represents the aggregate response of a plurality of photo-sensors

46. The image display claimed in claim 1, wherein the display is a color display having differently colored light emitters, separate photo-sensors generate feedback signals for each color, and the feedback control circuit controls the desired light output for each color of the display.