Holographic illumination system

• US 6,115,152 A
• Filed: 09/14/1999
• Issued: 09/05/2000
• Est. Priority Date: 09/14/1998
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: DigiLens Inc
• Inventors: Popovich, Milan M., Storey, John J., Waldern, Jonathan D.
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): BOUTSIKARIS, LEONIDAS
• Application Number:
  US09/395,889
• Time in Patent Office: 357 Days
• Field of Search: 359/15, 359/22, 359/24, 359/618, 359/629, 359/634, 353/30, 353/31, 353/34, 349/201, 349/202
• US Class Current: 359/15
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02F 1/13342 Holographic polymer dispersed liquid crystals
• CPC Class Codes: G02F 1/133621 providing coloured light G02F1/133617, G02F1/133533 take precedence
• CPC Class Codes: G02F 1/133622 Colour sequential illumination
• CPC Class Codes: G02F 1/13473 for wavelength filtering or for colour display without the use of colour mosaic filters
• CPC Class Codes: G02F 1/291 Two-dimensional analogue deflection
• CPC Class Codes: G02F 1/292 by controlled diffraction or phased-array beam steering controlled diffraction for optical switching G02F1/31
• CPC Class Codes: G02F 2201/346 distributed (Bragg) reflector
• CPC Class Codes: G03H 1/26 Processes or apparatus specially adapted to produce multiple sub- holograms or to obtain images from them, e.g. multicolour technique

Abstract

Holographic optical elements (HOEs) can be used in systems and methods for providing illumination and for projecting images. The HOEs may be switchable HOEs, whose diffractive properties can be controlled. Described herein is a method of combining light from two or more illumination sources. In one embodiment, a reflection-type HOE is illuminated by the first illumination source. The HOE diffracts light from the first illumination source into an output direction. Light from the second illumination source is transmitted through the HOE and onto a reflective optical element, which reflects the light back through the HOE and into the same output direction. Also described is a projection system that uses two or more HOEs to combine two or more colors of light for use by a single image display. The system includes one or more light sources, an image display (such as a reflective or transmissive LCD display or a MEMS display, for example), and a first and a second HOE. The HOEs are each mounted between a light source and the image display, and configured to provide one color of light to the image display and from the image display into an output direction. In one embodiment, the HOEs are switchable HOEs and can be used for color-sequential display and/or for color balancing.

Claims

1. A method of combining light from a first illumination source and a second illumination source, the method comprising:

illuminating a switchable holographic optical element (HOE) with light from the first illumination source;

the switchable HOE diffracting light from the first illumination source into an output direction;

transmitting light from the second illumination source through the switchable HOE and onto an optical element;

the optical element deflecting the light transmitted through the switchable HOE from the second illumination source into the output direction.

2. The method of claim 1, wherein the optical element is a second switchable HOE and wherein said deflecting the light comprises diffracting light from the second switchable HOE.

3. The method of claim 1, wherein the switchable HOE operates between an active state and an inactive state, wherein the switchable HOE diffracts light when operating in the active state, wherein the switchable HOE transmits substantially all light without substantial alteration when operating in the inactive state.

4. The method of claim 1, further comprising:

the switchable HOE modifying a spatial profile of the light from the first illumination source.

5. The method of claim 1, wherein the switchable HOE is configured to provide substantially spatially uniform illumination in the output direction.

6. The method of claim 1, wherein at least one of the first and second illumination sources is a narrowband illumination source.

7. The method of claim 1, wherein the first illumination source provides light of a different color than light from the second illumination source.

8. The method of claim 1, wherein at least one of the first and second illumination sources is a laser or a light-emitting diode.

9. The method of claim 1, wherein at least one of the first and second illumination sources is an incandescent bulb or a fluorescent bulb or a halogen lamp or an arc lamp or an induction lamp.

10. The method of claim 1, wherein said deflecting the light comprises deflecting light transmitted through the switchable HOE from the second illumination source so that the deflected light from the second illumination source substantially overlaps with diffracted light from the first illumination source.

11. An illumination system comprising:

a switchable holographic optical element (HOE) configured to diffract light from a first light source into an output direction;

an optical element disposed so that light transmitted from a second light source through said switchable HOE is incident on said optical element, wherein said optical element is configured to deflect switchable HOE-transmitted light from the second light source into the out put direction.

12. The illumination system of claim 11, wherein said optical element is a second switchable HOE configured to diffract switchable HOE-transmitted light from the second light source into the output direction.

13. The illumination system of claim 11, wherein said optical element is a mirror aligned to reflect switchable HOE-transmitted light from the second light source into the output direction.

14. The illumination system of claim 11, wherein said switchable HOE operates between an active state and an inactive state, wherein said switchable HOE diffracts light when operating in the active state, wherein said switchable HOE transmits substantially all light without substantial alteration when operating in the inactive state.

15. The illumination system of claim 11, wherein said switchable HOE is further configured to modify a spatial profile of the light from the first light source.

16. The illumination system of claim 11, wherein said switchable HOE is further configured to provide spatially uniform illumination in the output direction.

17. The illumination system of claim 11, wherein at least one of the first and second light sources is a narrowband light source.

18. The illumination system of claim 11, wherein the first light source provides light of a different color than light from the second light source.

19. The illumination system of claim 11, wherein at least one of the first and second light sources is a laser or a light-emitting diode.

20. The illumination system of claim 11, wherein at least one of the first and second light sources is an incandescent bulb or a fluorescent bulb or a halogen lamp or an arc lamp or an induction lamp.

21. The illumination system of claim 11, wherein said optical element is configured to deflect switchable HOE-transmitted light from the second illumination source to overlap with diffracted light from the first illumination source.