Light emitting device driving method and projection apparatus so equipped

• US 20050243223A1
• Filed: 04/30/2004
• Published: 11/03/2005
• Est. Priority Date: 04/30/2004
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: InFocus Corporation (Lap-Shun Hui, MBA)
• Inventors: Slobodin, David E.
• Granted Patent: US 7,408,527 B2
• Time in Patent Office: Days
• US Class Current: 349/7
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2310/066 Waveforms comprising a gently increasing or decreasing portion, e.g. ramp
• CPC Class Codes: G09G 2320/062 Adjustment of illumination source parameters
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: H04N 9/3114 by using a sequential colour filter producing one colour at a time
• CPC Class Codes: H04N 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20

Abstract

A projection system is provided with a controller equipped to drive light emitting devices of a light source of the projection system in a manner that enhances the operational life of the light emitting devices, the ability to provide peak white, and/or finer gray scale.

Claims

1. In a projection apparatus, a method of operation comprising:

receiving a signal of one or more frames of visual images; and

applying a first substantially constant level of current to drive a first light emitting device of a light source for a first portion of a frame period to cause the first light emitting device to emit light of a first color during the first portion of the frame period to render a frame of the visual images, the first light emitting device having an operational life characteristic that is dependent at least in part on drive current employed to drive the first light emitting device, and the first substantially constant level of current applied being selected in view of at least the first light emitting device'"'"'s operational life characteristic dependency on drive current, and the size of the first portion of the frame period relative to the size of the entire frame period.

2. The method of claim 1, wherein the first color is a selected one of a red primary color, a blue primary color and a green primary color.

3. The method of claim 1, wherein the size of the first portion of the frame period is about 1/n of the entire frame period, and the first substantially constant level of current applied is substantially inversely proportional to 1/n, where n is an integer.

4. The method of claim 1, wherein the method further comprises applying a second substantially constant level of current to drive a second light emitting device of the light source for a second portion of the frame period to cause the second light emitting device to emit light of a second color during the second portion of the frame period to render the same frame of the visual images, the second light emitting device having an operational life characteristic that is dependent on drive current employed to drive the second light emitting device, and the second substantial constant level being selected in view of at least the second light emitting device'"'"'s operational life characteristic dependency on drive current, and the size of the second portion of the frame period relative to the size of the entire frame period.

5. The method of claim 4, wherein the first color is a selected one of a red primary color, a blue primary color and a green primary color;

and the second color is a selected one of the unselected primary colors.

6. The method of claim 4, wherein the method further comprises applying the first and second substantially constant levels of current to drive the first and second light emitting devices of the light source respectively for a third portion of the frame period to cause the first and second light emitting devices to emit light of the first and second colors respectively during the third portion of the frame period to render the image frame.

7. The method of claim 6, wherein the size of the first and third portion combined is about 1/n of the frame period, and the first substantially constant level of current applied is substantially inversely proportional to 1/n, where n is an integer.

8. The method of claim 6, wherein the size of the second and third portion combined is about 1/n of the frame period, and the second substantially constant level of current applied is substantially inversely proportional to 1/n, where n is an integer.

9. The method of claim 6, wherein said applying of the first and second substantially constant levels of current to drive the first and second light emitting devices of the light source respectively for a third portion of the frame period is conditionally performed based at least in part on the content of the frame of the visual images being rendered.

10. The method of claim 9, wherein the method further comprises dynamically selecting the sizes of said first, second and third portions.

11. The method of claim 1, wherein said applying comprises applying a first variable level of current during said first portion of the frame period instead, and the time average of the first variable current applied being selected in view of at least the first light emitting device'"'"'s operating life characteristic dependency on drive current, and the size of the first portion of the frame period relative to the size of the entire frame period.

12. The method of claim 11, wherein the first variable level of current applied during the first portion of the frame period has a form factor selected from a function group consisting of a step function having one or more steps, and a sawtooth function having a plurality of sawtooth.

13. The method of claim 11, wherein the first variable level of current applied during the first portion of the frame period varies non-linearly.

14. The method of claim 11, wherein the method further comprises selectively turning on and off of a light valve one or more times during the first portion of the frame period.

15. The method of claim 14, wherein said selectively turning on and off of a light valve comprises selectively turning on and off one or more micro-mirrors of a micro-mirror device one or more times during the first portion of the frame period.

16. In a projection apparatus, a method of operation comprising:

receiving a signal of one or more frames of visual images;

applying a first level of current to drive a first light emitting device of a light source for a first portion of a frame period to cause the first light emitting device to emit light of a first color during the first portion of the frame period to render a frame of the visual images;

applying a second level of current to drive a second light emitting device of the light source for a second portion of the frame period to cause the second light emitting device to emit light of a second color during the second portion of the frame period to render the frame of the visual images; and

applying the first and second levels of current to drive the first and second light emitting devices of the light source for a third portion of the frame period to cause the first and second light emitting devices to emit light of the first and second colors respectively, during the third portion of the frame period to render the frame of the visual images.

17. The method of claim 16, wherein said applying of the first and second levels of current to drive the first and second light emitting devices of the light source respectively for a third portion of the frame period is conditionally performed based at least in part on the content of the frame of the visual images being rendered.

18. The method of claim 17, wherein the method further comprises dynamically selecting the sizes of said first, second and third portions.

19. The method of claim 16, wherein at least one of said applying of the first level of current to said first light emitting device, said applying of the second level of current to said second light emitting device, and said joint applying of the first and second levels of current to said first and second light emitting devices respectively comprises applying a variable level of current.

20. The method of claim 19, wherein the method further comprises selectively turning on and off of a light valve one or more times during the corresponding portion(s) of the frame period.

21. In a projection apparatus, a method of operation comprising:

receiving a signal of one or more frames of visual images;

applying a variable level of current to drive a light emitting device of a light source for a portion of a frame period to cause the light emitting device to variably emit light of a color during the portion of the frame period to render a frame of the visual images; and

selectively turning on and off a light valve one or more times during the portion of the frame period.

22. The method of claim 21, wherein the variable level of current applied during the portion of the frame period has a form factor selected from a function group consisting of a step function having one or more steps, and a sawtooth function having a plurality of sawtooth.

23. The method of claim 21, wherein the variable level of current applied during the portion of the frame period varies non-linearly.

24. The method of claim 21, wherein said selectively turning on and off of a light valve comprises selectively turning on and off one or more micro-mirrors of a micro-mirror device one or more times during the portion of the frame period.

25. In a projection apparatus, a method of operation, comprising:

controlling a first colored light source in a first time varying intensity manner during a first time period; and

complementarily controlling a light valve of a pixel in an on state during at least a portion of the first time period, to contribute towards achieving a desired grayscale for the pixel.

26. The method of claim 25, wherein the method further comprises controlling a second colored light source in a second time varying intensity manner during a second time period, and complementarily controlling the light valve of the pixel in said on state during at least a portion of the second time period, to further contribute towards achieving the desired grayscale for the pixel.

28. The projection apparatus of claim 26, wherein the controller is further coupled to the light source to apply a second substantially constant level of current to drive a second light emitting device of the light source for a second portion of the frame period to cause the second light emitting device to emit light of a second color during the second portion of the frame period to render the same frame of the visual images, the second light emitting device having an operational life characteristic that is dependent on drive current applied to drive the second light emitting device, and the second substantial constant level being selected in view of at least the operational life characteristic dependency on the drive current, and the size of the second portion of the frame period relative to the size of the entire frame period.

29. The projection apparatus of claim 28, wherein the controller is further coupled to the light source to apply the first and second substantially constant levels of current to drive the first and second light emitting devices of the light source respectively for a third portion of the frame period to cause the first and second light emitting devices to emit light of the first and second colors respectively during the third portion of the frame period to render the image frame.

30. The projection apparatus of claim 29, wherein the controller is further equipped to perform said application of the first and second substantially constant levels of current to drive the first and second light emitting devices of the light source respectively for a third portion of the frame period conditionally, based at least in part on the content of the image frame being rendered.

31. The projection apparatus of claim 30, wherein the controller is further equipped to dynamically select the sizes of said first, second and third portions.

27. A projection apparatus comprising:

projection optics;

a light source optically coupled to the projection optics to emit light for the projection optics; and

a controller electrically coupled to the light source to control emission of light by the light source, including application of a first substantially constant level of current to drive a first light emitting device of the light source for a first portion of a frame period to cause the first light emitting device to emit light of a first color during the first portion of the frame period to render an image frame, the first light emitting device having an operational life characteristic that is dependent on drive current applied to drive the first light emitting device, and the first substantially constant level of current applied being selected in view of at least the operational life characteristic dependency on drive current, and the size of the first portion of the frame period relative to the size of the entire frame period.

32. The projection apparatus of claim 27, wherein the controller is equipped to perform said applying by applying a first variable level of current during said first portion of the frame period instead, and the time average of the first variable level current applied during said first portion of the frame period being selected in view of at least the operational life characteristic dependency on drive current, and the size of the first portion of the frame period relative to the size of the entire frame period.

33. The projector apparatus of claim 32, wherein the projection optics comprise a light valve, and the controller is further electrically coupled to the light valve as well as equipped to selectively turn on and off of the light valve one or more times during the first portion of the frame period.

34. The projector apparatus of claim 33, wherein said light valve comprises a micro-mirror device, and said the controller is equipped to selectively turn on and off one or more micro-mirrors of the micro-mirror device one or more times during the first portion of the frame period.

35. A projection apparatus, comprising:

projection optics;

a light source optically coupled to the projection optics to emit light for the projection optics; and

a controller electrically coupled to the light source to apply

a first level of current to drive a first light emitting device of the light source for a first portion of a frame period to cause the first light emitting device to emit light of a first color during the first portion of the frame period to render a frame of visual image,

a second level of current to drive a second light emitting device of the light source for a second portion of the frame period to cause the second light emitting device to emit light of a second color during the second portion of the frame period to render the frame of visual image, and

the first and second levels of current to drive the first and second light emitting devices of the light source for a third portion of the frame period to cause the first and second light emitting devices to emit light of the first and second colors respectively, during the third portion of the frame period to render the frame of visual image.

36. The projector apparatus of claim 35, wherein said controller is equipped to perform said applying of the first and second levels of current to drive the first and second light emitting devices of the light source respectively for a third portion of the frame period conditionally, based at least in part on the content of the frame of visual image being rendered.

37. The projector apparatus of claim 36, wherein said controller is further equipped to dynamically select the sizes of said first, second and third portions.

38. The projector apparatus of claim 36, wherein said controller is equipped to perform at least one of said applying of the first level of current to said first light emitting device, said applying of the second level of current to said second light emitting device, and said joint applying of the first and second levels of current to said first and second light emitting devices respectively, by applying a variable level of current.

39. The projector apparatus of claim 36, wherein the projection optics comprises a light valve, and the controller is further electrically coupled to the light valve, as well as being equipped to selectively turn on and off of the light valve one or more times during the corresponding portion(s) of the frame period.

40. A projection apparatus, comprising:

projection optics including a light valve;

a light source optically coupled to the projection optics to emit light for the projection optics; and

a controller electrically coupled to the light source and the light valve to

apply a variable level of current to drive a light emitting device of the light source for a portion of a frame period to cause the light emitting device to variably emit light of a color during the portion of the frame period to render a frame of the visual images, and

selectively turn on and off of a light valve one or more times during the portion of the frame period.

41. The projection apparatus of claim 40, wherein the light valve comprises a micro-mirror device, and the controller is equipped to perform said selectively turning on and off of the light valve by selectively turning on and off one or more micro-mirrors of a micro-mirror device one or more times during the portion of the frame period.

42. A projection apparatus, comprising:

projection optics including a light valve;

a light source optically coupled to the projection optics to emit light for the projection optics; and

a controller electrically coupled to the light source and the light valve, and adapted

to control a first colored light source in a first time varying intensity manner during a first time period, and

to complementarily control a light valve of a pixel in an on state during at least a portion of the first time period, to contribute towards achieving a desired grayscale for the pixel.

43. The projection apparatus of claim 42, wherein the controller is further adapted to control a second colored light source in a second time varying intensity manner during a second time period, and to complementarily control the light valve of the pixel in said on state during at least a portion of the second time period, to further contribute towards achieving the desired grayscale for the pixel.