LED array with photodetector

• US 8,264,431 B2
• Filed: 10/23/2003
• Issued: 09/11/2012
• Est. Priority Date: 10/23/2003
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Bulovic, Vladimir, Tischler, Jonathan R., Yu, Jennifer
• Primary Examiner(s): Cheng, Joe H
• Application Number:
  US10/693,022
• Publication Number:
  US 20050088380A1
• Time in Patent Office: 3,246 Days
• Field of Search: 345/77, 257/80, 349/62
• US Class Current: 345/77
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• 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 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3216 using a passive matrix
• CPC Class Codes: G09G 3/3225 using an active matrix

Abstract

Embodiments of the present invention provide for an array, and corresponding method of forming an array, that includes a plurality of light emitting devices. The light emitting devices are disposed over a substrate, and a photodetector detects light emitted through the substrate from the light emitting devices. Further, a substantially constant brightness may be maintained in a plurality of light emitting devices disposed over the upper surface of a substrate in an array. Light emitted through the substrate from each of the light emitting devices is measured, and the voltage level applied to each of the light emitting devices is varied to maintain a substantially constant brightness level of light emitted from the light emitting devices.

Claims

1. An array, comprising:

a plurality of light emitting devices disposed on a transparent substrate, the transparent substrate having an upper surface that contacts each light emitting device, a lower surface distal from the plurality of light emitting devices and a plurality of side surfaces, each of the side surfaces being substantially perpendicular to the upper surface,

wherein each of the plurality of light emitting devices is individually addressed to display an image; and

at least one photodetector non-removably flush mounted, with a detector side facing the plurality of light emitting devices, on an external face of the lower surface of the transparent substrate for detecting a fraction of waveguided light emitted from the plurality of light emitting devices, wherein another fraction of waveguided light is edge emitted, wherein the fraction of waveguided light and the another fraction of waveguided light is directly observable.

2. The array of claim 1, further comprising at least one additional photodetector formed over outer periphery edges of the upper surface.

3. The array of claim 1, further comprising a feedback circuit that measures a brightness level for each of the plurality of light emitting devices, and varies a voltage applied to individual ones of the light emitting devices to maintain a brightness level of each of the light emitting devices at a substantially constant level.

4. The array of claim 3, wherein the feedback circuit includes a compensation factor generator for generating a compensation factor for each of the plurality of light emitting devices and a memory array for storing the compensation factor for each of the plurality of light emitting devices.

5. The array of claim 3, wherein the feedback circuit varies the voltage applied independently to the individual ones of the light emitting devices to maintain the brightness level of each of the light emitting devices at a substantially constant level.

6. The array of claim 1, wherein each of the plurality of light emitting devices is selectively activated to display the image.

7. A display comprising the array of claim 1.

8. A method for forming an array, comprising:

forming a plurality of light emitting devices disposed on a transparent substrate, said transparent substrate having an upper surface contacting each light emitting device, a lower surface distal from the light emitting device and at least one side surface substantially perpendicular to said upper surface of the transparent substrate, wherein each of the plurality of light emitting devices is individually addressed to display an image; and

non-removably flush mounting, with a detector side facing the plurality of light emitting devices, a photodetector at the lower surface of the transparent substrate for detecting a fraction of waveguided light emitted through the transparent substrate, wherein another fraction of waveguided light is edge emitted, wherein the fraction of waveguided light and the another fraction of waveguided light is directly observable.

9. The method of claim 8, further comprising forming at least another photodetector on the side surface of the transparent substrate.

10. The method of claim 8, wherein the photodetector includes a plurality of photodetectors.

11. The method of claim 10, further comprising forming at least one of the photodetectors on each of the side surfaces.

12. The method of claim 8, further comprising forming a feedback circuit that measures a brightness level for each of the plurality of light emitting devices, and varies a voltage applied to individual ones of the light emitting devices to maintain a brightness level of each of the light emitting devices at a substantially constant level.

13. The method of claim 12, further comprising forming the feedback circuit with a compensation factor generator for generating a compensation factor for each of the plurality of light emitting devices and a memory array for staring the compensation factor for each of the plurality of light emitting devices.

14. The method of claim 8, wherein each of the plurality of light emitting devices is selectively activated to display the image.

15. An array, comprising:

a plurality of light emitting devices formed on a surface of a transparent substrate, the transparent substrate having an upper surface that contacts each light emitting device, a lower surface distal from the light emitting device and a plurality of side surfaces,

wherein each of the plurality of light emitting devices is individually addressed to display an image; and

at least two photodetectors non-removably flush mounted, with a detector side facing the plurality of light emitting devices, on an external opposite surface of the transparent substrate for detecting a fraction of waveguided light emitted from the plurality of light emitting devices, wherein another fraction of waveguided light is edge emitted, wherein the fraction of waveguided light and the another fraction of waveguided light is directly observable.

16. The array of claim 15, further comprising at least one additional photodetector formed over outer periphery edges of the surface of the transparent substrate.

17. The array of claim 15, further comprising a feedback circuit that measures a brightness level for each of the plurality of light emitting devices, and varies a voltage applied to individual ones of the light emitting devices to maintain a brightness level of each of the light emitting devices at a substantially constant level.

18. The array of claim 17, wherein the feedback circuit includes a compensation factor generator for generating a compensation factor far each of the plurality of light emitting devices and a memory array for storing the compensation factor for each of the plurality of light emitting devices.

19. The array of claim 15, wherein each of the plurality of light emitting devices is selectively activated to display the image.

20. An array, comprising:

a plurality of light emitting devices disposed over a substrate having an upper surface that contacts each of the light emitting devices, a lower surface distal from the plurality of light emitting devices and a plurality of side surfaces,

wherein each of the plurality of light emitting devices is individually addressed to display an image; and

a photodetector that detects a fraction of waveguided light emitted through the substrate from the plurality of light emitting devices and wherein another fraction of waveguided light is emitted at the edge of the substrate, wherein the fraction of waveguided light and the another fraction of waveguided light is directly observable, wherein the photodetector is non-removably flush mounted, with a detector side facing the plurality of light emitting devices, on the lower surface and wherein at least one light emitting device comprises an OLED.

21. The array of claim 20 further comprising a feedback circuit that measures a brightness level for each of the plurality of light emitting devices, and varies a voltage applied to individual ones of the light emitting devices to maintain a brightness level of each of the light emitting devices at a substantially constant level.

22. The array of claim 21, wherein the feedback circuit includes a compensation factor generator for generating a compensation factor for each of the plurality of light emitting devices and a memory array for storing the compensation factor for each of the plurality of light emitting devices.

23. The array of claim 20, wherein each of the plurality of light emitting devices is selectively activated to display the image.

24. An array, comprising:

a plurality of fight emitting devices disposed over a substrate having an upper surface that contacts each of the light emitting devices, a lower surface distal from the plurality of light emitting devices and a plurality of side surfaces,

wherein each of the plurality of light emitting devices is individually addressed to display an image; and

a photodetector that detects a fraction of waveguided light emitted through the substrate from the plurality of light emitting devices and wherein another fraction of waveguided light is emitted at the edge of the substrate, wherein the fraction of waveguided light and the another fraction of waveguided light is directly observable, wherein the photodetector is non-removably flush mounted, with a detector side facing the plurality of light emitting devices, on the lower surface and wherein at least one light emitting device comprises a PLED.

25. The array of claim 24, further comprising a feedback circuit that measures a brightness level for each of the plurality of light emitting devices, and varies a voltage applied to individual ones of the light emitting devices to maintain a brightness level of each of the light emitting devices at a substantially constant level.

26. The array of claim 25, wherein the feedback circuit includes a compensation factor generator for generating a compensation factor for each of the plurality of light emitting devices and a memory array for storing the compensation factor for each of the plurality of light emitting devices.

27. The array of claim 24, wherein each of the plurality of light emitting devices is selectively activated to display the image.

28. An array, comprising:

a plurality of light emitting devices disposed over a substrate having an upper surface that contacts each of the light emitting devices, a lower surface distal from the plurality of light emitting devices and a plurality of side surfaces,

wherein each of the plurality of light emitting devices is individually addressed to display an image; and

a photodetector that detects a fraction of waveguided light emitted through the substrate from the plurality of light emitting devices and wherein another fraction of waveguided light is emitted at the edge of the substrate, wherein the fraction of waveguided light and the another fraction of waveguided light is directly observable wherein the photodetector is non-removably flush mounted, with a detector side facing the plurality of light emitting devices, on the lower surface and wherein at least one light emitting device comprises a QDLED.

29. The array of claim 28, further comprising a feedback circuit that measures a brightness level for each of the plurality of light emitting devices, and varies a voltage applied to individual ones of the light emitting devices to maintain a brightness level of each of the light emitting devices at a substantially constant level.

30. The array of claim 29, wherein the feedback circuit includes a compensation factor generator for generating a compensation factor for each of the plurality of light emitting devices and a memory array for storing the compensation factor fur each of the plurality of light emitting devices.

31. The array of claim 28, wherein each of the plurality of light emitting devices is selectively activated to display the image.

32. A display comprising the array of claim 28.