Planar polarizer for LCD projectors

• US 5,940,149 A
• Filed: 12/11/1997
• Issued: 08/17/1999
• Est. Priority Date: 12/11/1997
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Company
• Inventors: Vanderwerf, Dennis F.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): DUDEK, JAMES A
• Application Number:
  US08/988,899
• Time in Patent Office: 614 Days
• Field of Search: 349/5, 349/96, 359/487, 359/488, 359/496, 359/497, 359/833, 359/834
• US Class Current: 349/5
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 27/285 comprising arrays of elements, e.g. microprisms
• CPC Class Codes: G02B 5/045 Prism arrays

Abstract

A liquid crystal display projector including a light source, a collimator lens, a planar polarization converter, a liquid crystal display panel, and projection lenses. The collimator lens is optically aligned to receive a beam of light from the light source and to produce a collimated light beam. The planar polarization converter is optically aligned in front of the collimator lens to receive the collimated beam of light. The polarization converter includes a prismatic film having a first prismatic surface, a reflective polarization film, and a quarter wave retarder film positioned between the prismatic film and the polarization film sheet. The prismatic surface has alternating transmissive prismatic facets and reflective prismatic facets positioned at supplementary base angles, the reflective prismatic facets positioned at a second base angle β and the transmissive prismatic facets positioned at a first base angle generally equal to 180°-β.

Claims

1. A planar polarization converter for polarizing a beam of light, the order of incidence along the optical path of the beam of light defining front and back positions, the polarization converter comprising:

a prismatic film having a first prismatic surface, the first prismatic surface having alternating transmissive prismatic facets and reflective prismatic facets positioned at supplementary base angles, the reflective prismatic facets positioned at a second base angle β and

the transmissive prismatic facets positioned at a first base angle generally equal to 180°

-β

;

a quarter wave retarder film; and

a reflective polarization film, wherein the quarter wave retarder film is positioned between the prismatic film and the polarization film sheet.

2. The planar polarization converter of claim 1, further comprising a light deviator assembly positioned in front of the prismatic film, wherein the light deviator assembly directs the beam of light in the base angle β

.

3. The planar polarization converter of claim 2, wherein the light deviator assembly comprises a light deviating prismatic sheet.

4. The planar polarization converter of claim 2, wherein the light deviator assembly comprises a light deviating prismatic sheet and a collimating lens.

5. The planar polarization converter of claim 2, wherein the light deviator assembly comprises a collimating lens positioned at a base angle generally equal to 180°

-β

.

6. The planar polarization converter of claim 1, wherein β

generally equals 45°

.

7. The planar polarization converter of claim 1, further comprising an absorbing polarizer positioned behind the reflective polarization film.

8. The planar polarization converter of claim 7, wherein the quarter wave retarder film, the reflective polarizer film, and the absorbing polarizer film are stacked and mounted on a glass substrate.

9. The planar polarization converter of claim 1, further comprising a beam integrating film positioned behind the reflective polarization film.

10. The planar polarization converter of claim 1, the prismatic film having a second prismatic surface having alternating first and second transmissive facets, wherein the first transmissive facets are generally parallel to the transmissive prismatic facets of the first prismatic surface and the second transmissive facets are generally parallel to the reflective prismatic facets of the first prismatic surface.

11. The planar polarization converter of claim 1 wherein the reflective prismatic facets of the first prismatic surface include a plurality of retroreflective microprisms.

12. The planar polarization converter of claim 11, the microprisms having a vertex angle α

, wherein α

+2β

=180°

.

13. The planar polarization converter of claim 2, the light deviation assembly comprising a first and a second prismatic element, wherein the first prismatic element deviates the beam of light a first deviation angle φ

and the second prismatic element deviates the beam of light a second deviation angle.

14. The planar polarization converter of claim 13, the first and a second prismatic elements each having alternating first and second prismatic surfaces, wherein the first prismatic surface of the second prismatic element is oriented at the first deviation angle φ

, the second prismatic surface of the first prismatic element is oriented parallel to the incident light beam, and the second prismatic surface of the second prismatic element is oriented at φ

+90°

.

15. The planar polarization converter of claim 14, wherein the first prismatic surface of the first prismatic element is oriented at a base angle generally equal to φ

, where φ

is equal to or greater than the angle of total internal reflection of the original beam of light.

16. The planar polarization converter of claim 1, the planar polarization sheet having a tilted polarization transmission axis.

17. An liquid crystal display panel including the planar polarization converter of claim 1.

18. A planar polarization converter for polarizing a beam of light, the order of incidence along the optical path of the beam of light defining front and back positions, the polarization converter comprising:

a light deviator assembly, wherein the light deviator assembly directs the beam of light in an angle β

;

a dual sided prismatic film having a first prismatic surface and a second prismatic surface, the first prismatic surface having alternating transmissive prismatic facets and reflective prismatic facets positioned at supplementary angles, the reflective prismatic facets positioned at a second base angle generally equal to β

, the transmissive prismatic facets positioned at a first base angle generally equal to 180°

-β

, the surface of the reflective prismatic facets having a plurality of retroreflective microprisms, the second prismatic surface having alternating first and second transmissive facets, wherein the first transmissive facets are generally parallel to the transmissive prismatic facets of the first prismatic surface and the second transmissive facets are generally parallel to the reflective prismatic facets of the first prismatic surface;

a quarter wave retarder film;

a planar reflective polarization film sheet, wherein the quarter wave retarder film is positioned between the prismatic film and the reflective polarization film sheet;

an absorbing polarization film positioned behind the reflective polarization film, both polarization films aligned along the same polarization axis; and

a beam integrating film positioned behind the absorbing polarization film.

19. A liquid crystal display projector comprising:

a light source producing a beam of light;

a collimator lens optically aligned to receive the beam of light and produce a collimated light beam;

a planar polarization converter optically aligned to receive the collimated light beam and produce a polarized light beam, the polarization converter including;

a prismatic film having a first prismatic surface, the prismatic surface having alternating transmissive prismatic facets and reflective prismatic facets positioned at supplementary base angles, the reflective prismatic facets positioned at a second base angle β and

the transmissive prismatic facets positioned at a first base angle generally equal to 180°

-β

,

a quarter wave retarder film, and

a reflective polarization film sheet, wherein the quarter wave retarder film is positioned between the prismatic film and the reflective polarization film sheet;

a liquid crystal display panel optically aligned with the polarization converter to receive the polarized light beam and produce an image beam; and

a projection lens assembly optically aligned with the liquid crystal panel to receive the image beam.

20. The liquid crystal display projector of claim 19, further comprising a glass condenser between the light source and the collimator lens, and wherein the projection lens assembly includes a converging Fresnel lens and at least one projection lens optically aligned with respect to each other.

21. The liquid crystal projector of claim 19, further comprising a light deviation assembly optically aligned to receive the collimated light beam from the collimator lens, wherein the light deviation assembly directs the beam of light in the angle β

.

22. The liquid crystal projector of claim 21, wherein the collimator lens and the light deviation assembly are parallel with respect to each other and positioned at an angle with respect to the planar polarization converter.

23. The liquid crystal projector of claim 19, wherein β

is approximately equal to 45°

.

24. The liquid crystal projector of claim 19, wherein the collimator lens is oriented at a angle with respect to the planar polarization converter.

25. The liquid crystal projector of claim 24, further comprising a mirror optically aligned to reflect the beam of light towards the collimator lens.

26. The liquid crystal projector of claim 24, the collimator lens being a reflective collimator.