Illumination modulation technique for microdisplays

• US 9,082,347 B2
• Filed: 01/19/2005
• Issued: 07/14/2015
• Est. Priority Date: 01/19/2005
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Willis, Thomas E.
• Primary Examiner(s): ABDULSELAM, ABBAS I
• Application Number:
  US11/038,292
• Publication Number:
  US 20060158465A1
• Time in Patent Office: 3,828 Days
• Field of Search: 345/204, 345690-693, 345/691
• US Class Current: 1/1
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/34 by control of light from an independent source
• CPC Class Codes: H04N 9/3114 by using a sequential colour filter producing one colour at a time
• CPC Class Codes: H04N 9/3123 using pulse width modulation

Abstract

A projection display may use pulse width modulation wherein the duty cycle may be varied. This duty cycle variation may improve bit depth in some embodiments. For example, on alternate frames, the duty cycle may be reduced by a given percentage.

Claims

1. A method comprising:

pulse width modulating the duty cycle of a light beam to establish a pixel intensity; and

varying the duty cycle between two frames by reducing the duty cycle in at least two successive even frames by a first amount and in at least two successive odd frames by a second amount different than said first amount.

2. The method of claim 1 including reducing the duty cycle for a darker pixel relative to a lighter pixel.

3. The method of claim 1 including varying the duty cycle in a successive frame.

4. The method of claim 1 including alternating between two duty cycles in successive frames.

5. The method of claim 4 including providing a 50% duty cycle for a first set of frames, and reducing the duty cycle in another set of frames.

6. The method of claim 5 including reducing the duty cycle between about 2 and about 10%.

7. The method of claim 1 including alternating the duty cycle using a modulo function.

8. The method of claim 7 including providing a lookup table to determine how to reduce the duty cycle.

9. The method of claim 8 including providing different intensity values for different pixels and adjusting the duty cycle based on a frame number.

10. A projection display comprising:

a spatial light modulator; and

a device to periodically reduce the duty cycle of pulse width modulation between two frames for darker relative to lighter pixels.

11. The display of claim 10 wherein said device to reduce the duty cycle for a darker pixel relative to a lighter pixel.

12. The display of claim 10 wherein said device to vary the duty cycle in successive frames.

13. The display of claim 12 wherein said device to change the duty cycle in every other frame.

14. The display of claim 10 wherein said device to alternate the duty cycles in successive frames.

15. The display of claim 14 wherein said device to provide a 50% duty cycle in a first set of frames and reduced duty cycles in another set of frames.

16. The display of claim 15 wherein said device to reduce the duty cycle selectively between about 2 and about 10%.

17. The display of claim 10 wherein said device to implement a modulo function to reduce the duty cycle.

18. The display of claim 17 wherein said device includes a lookup table to determine how to reduce the duty cycle.

19. The display of claim 18 wherein said device to provide different intensity values for different pixels and adjust the duty cycle based on the frame number.

20. A spatial light modulator comprising:

a modulating panel; and

a device to vary the duty cycle of pulse width modulation of said modulator between successive frames by reducing the duty cycle in at least two successive even frames by a first amount and in at least two successive odd frames by a second amount different than said first amount.

21. The modulator of claim 20, said device to reduce the duty cycle for a darker pixel relative to a lighter pixel.

22. The modulator of claim 20, said device to vary the duty cycle in successive frames.

23. The modulator of claim 22 wherein said device to change the duty cycle in every other frame.

24. The modulator of claim 20, said device to alternate the duty cycles in successive frames.