Optical display system including a light valve

• US 6,005,722 A
• Filed: 09/04/1998
• Issued: 12/21/1999
• Est. Priority Date: 09/04/1998
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Hubby, Laurence M. Jr., Butterworth, Mark M.
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Spector, David N.
• Application Number:
  US09/148,465
• Time in Patent Office: 473 Days
• Field of Search: 349/5, 349/7, 353/84, 353/31, 353/33, 353/37, 353/98, 359/618, 359/267, 359/712, 359/722, 359/723, 359/889, 359/890, 359/891, 348/742, 348/743, 348/744, 385/88, 385/133, 385/146
• US Class Current: 359/712
• CPC Class Codes: G02B 13/22 Telecentric objectives or lens systems
• CPC Class Codes: G02B 26/008 in the form of devices for effecting sequential colour changes, e.g. colour wheels
• CPC Class Codes: G02B 27/286 for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34
• CPC Class Codes: H04N 9/3114 by using a sequential colour filter producing one colour at a time

Abstract

An optical display system includes a light source, a color wheel, an optical train and a light valve. The optical train includes a diffuser element, a compound parabolic concentrator and an integrator. The diffuser element diffuses incoming light to fill in holes in cone half-angle distribution of light generated by the light source. The compound parabolic concentrator reduces the cone half-angle of the diffused light to a cone half-angle expected by the light valve. The integrator reduces hot spots in the diffused light. The color wheel may modulate optical path length of light traveling through the color wheel. Modulating the optical path length reduces coherence in the light generated by the light source. A color wheel that reduces coherence would allow the light source to be laser or LED-based. If the light valve is a ferroelectric light valve, the color wheel may include pairs of polarizers. Light is polarized in orthogonal directions by the polarizers in a pair. This allows all of the light to be used by the ferroelectric light valve during dc balancing.

Claims

1. An optical display system comprising:

a light source;

at least one light valve; and

an optical train in optical communication with the light source and at least one light valve, the optical train including a light pipe, the light pipe including a compound parabolic concentrator.

2. The system of claim 1, wherein the optical train further includes a 1:

1 telecentric relay in optical communication with the light valve and the compound parabolic concentrator, the compound parabolic concentrator being designed to change cone half-angle of incoming light.

3. The system of claim 1, wherein the light pipe further includes an integrator.

4. The system of claim 1, wherein the optical train further includes a diffuser element in front of the light pipe for filling in cone half-angles in light generated by the light source.

5. The system of claim 3, wherein an input face of the light pipe can diffuse incoming light to fill in cone half-angles in light generated by the light source.

6. The system of claim 5, wherein the input face is roughened.

7. The system of claim 5, wherein the input face is axicon-shaped.

8. The system of claim 1, wherein the compound parabolic concentrator has an output face, and wherein the optical train further includes a telecentric relay between the light valve and the compound parabolic concentrator, the telecentric relay having an aperture stop opposing the output face of the compound parabolic concentrator, the telecentric relay further including a lens group between the aperture stop and the light valve.

9. The system of claim 1, further comprising a rotatable color wheel disposed in an optical path between the light source and the optical train, a portion of the color wheel having a variable thickness for modulating optical path length.

10. The system of claim 9, wherein the light source includes at least one laser.

11. The system of claim 9, wherein the light source includes at least one LED.

12. The system of claim 1, wherein at least one light valve is a ferroelectric light valve, and wherein the color wheel has at least one pair of first and second polarizers, the first and second polarizers in each pair being adjacent, the polarities of the first and second polarizers in each pair being orthogonal.

13. The system of claim 1, wherein at least one light valve is a ferroelectric light valve, and wherein the color wheel includes red, green and blue filters separated by dark zones.

14. An optical display system comprising:

a light valve;

a source of white light;

means for splitting the white light into spectral components of the white light; and

an optical train between the splitting means and the light valve, the optical train including a compound parabolic concentrator for changing cone half-angle of light received from the splitting means.

15. An optical train for an optical display system, the optical train comprising:

a light pipe including compound parabolic concentrator for reducing cone half-angle of incoming light; and

a telecentric lens for imaging an output of the light pipe onto an imaging plane of the optical display system.

22. The optical train of claim 15, wherein the light pipe further includes an integrator.

23. The optical train of claim 15, further comprising a diffuser element in front of the light pipe for filling in cone half-angles in light generated by the light source.

24. The optical train of claim 15, wherein an input face of the light pipe can diffuse incoming light to fill in cone half-angles in light generated by the light source.

25. The optical train of claim 24, wherein the input face is roughened.

26. The optical train of claim 24, wherein the input face is axicon-shaped.

27. The optical train of claim 15, wherein the compound parabolic concentrator has an output face, and wherein the telecentric relay has an aperture stop opposing the output face of the compound parabolic concentrator, the telecentric relay further including a lens group between the aperture stop and the light valve.

16. A light pipe of an optical train for an optical display system, the light pipe comprising:

a compound parabolic concentrator for reducing cone half-angle of the incoming light; and

an integrator for reducing hot spots in the incoming light;

one of the integrator and the compound parabolic concentrator having an input face, the input face being adapted to diffuse incoming light;

the other of the integrator and the compound parabolic concentrator having an output face of the light pipe.

17. An optical display system comprising:

a light valve;

means for generating a beam of light;

a rotatable wheel including a region having a variable thickness for modulating optical path length that the light beam travels through the region, the modulation of the optical path length reducing the coherence in the beam; and

an optical train for imaging the color beam onto a light receiving surface of the light valve.

18. A color wheel for reducing coherence in a light beam in an optical display system, the color wheel comprising a region having a variable thickness for modulating optical path length that the light beam travels through the region, the modulation of the optical path length reducing the coherence in the beam.

28. The color wheel of claim 18, wherein the region has step-like variations in radial and circumferential directions.

19. An optical display system comprising:

a ferroelectric light valve;

means for generating a beam of white light;

a rotatable color wheel for filtering the white beam to produce a color beam, the color wheel including pairs of red, green and blue filters, each filter pair including first and second polarizers, the first and second polarizers in each pair being adjacent, the polarities of the first and second polarizers in each pair being orthogonal; and

an optical train for imaging the color beam onto a light receiving surface of the light valve.

29. The color wheel of claim 19, wherein the first polarizers filter the light during forward operation of the light valve, and wherein the second polarizers filter the light during dc balancing of the light valve.

20. A color wheel for an optical display system, the color wheel comprising pairs of red, green and blue filters, each filter pair including first and second polarizers, the first and second polarizers in each pair being adjacent, the polarities of the first and second polarizers in each pair being orthogonal.

21. An optical display system comprising:

a ferroelectric light valve;

means for generating a beam of white light;

a rotatable color wheel for filtering the white beam to produce a color beam, the color wheel including pairs of red, green and blue filters separated by dark zones; and

an optical train for imaging the color beam onto a light receiving surface of the light valve;

wherein the dark zones of the color wheel block the beam during dc balancing of the ferroelectric light valve.