Polarizing beam splitter

• US 6,721,096 B2
• Filed: 11/15/2002
• Issued: 04/13/2004
• Est. Priority Date: 10/28/1997
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Boyd, Gary T., Bruzzone, Charles L., Weber, Michael F., Eckhardt, Stephen K., Strharsky, Roger J., Aastuen, David J. W.
• Primary Examiner(s): Shafer, Ricky D.
• Application Number:
  US10/295,674
• Publication Number:
  US 20030184864A1
• Time in Patent Office: 515 Days
• Field of Search: 359/495, 359/496, 359/497, 359/498, 359/500
• US Class Current: 359/489.09
• CPC Class Codes: B29C 55/023 using multilayered plates or sheets
• CPC Class Codes: B29D 11/00 Producing optical elements, e.g. lenses or prisms grinding or polishing of optical elements B24B; constructional form of optical elements G02B; optical parts of spectacles G02C7/00
• CPC Class Codes: B29K 2995/003 Reflective
• CPC Class Codes: B29K 2995/0034 Polarising
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: G02B 27/1026 for use with reflective spatial light modulators
• CPC Class Codes: G02B 27/123 The splitting element being a lens or a system of lenses, including arrays and surfaces with refractive power
• CPC Class Codes: G02B 27/143 using macroscopically faceted or segmented reflective surfaces
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 27/149 using crossed beamsplitting surfaces, e.g. cross-dichroic cubes or X-cubes
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 5/305 including organic materials, e.g. polymeric layers
• CPC Class Codes: G02B 5/3058 comprising electrically conductive elements, e.g. wire grids, conductive particles
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

An optical imaging system including a wide-angle Cartesian polarizing beam splitter, light valve illumination optics having an f/#≦2.5, and at least one reflective light valve. The Cartesian polarizing beam splitter (PBS) has a structural orientation defining fixed polarization axes. The use of a Cartesian PBS allows the development of systems using curved PBS that provide higher light output and/or replace or augment other optical components. By recognizing and advantageously applying properties of wide-angle Cartesian polarizers, the present invention discloses a high-efficiency optical imaging system capable of functioning at f/#'"'"'s equal to or below f/2.5 while maintaining a contrast ratio of at least 100 to 1, or, more preferably, 150 to 1 in a projection system configuration.

Claims

1. A polarizing beamsplitter, comprising:

first and second prisms; and

a multiple layer, polarization-sensitive film disposed between the first and second prisms, the polarization-sensitive film being formed from alternating first and second polymer layers, the polarization-sensitive film having a structural orientation defining x- and y-polarization axes parallel to the film and a z-axis perpendicular to the film, the first polymer layer being birefringent and having a refractive index n_z substantially equal to one of n_x and n_y, where n_x, n_y and n_z are the refractive indices for light having electric field components parallel to the x-axis, y-axis and z-axis respectively;

wherein light propagating through the polarizing beamsplitter is refracted away from a normal to the polarization-sensitive film on passing from one of the first and second prisms to the polarization-sensitive film.

2. A polarizing beamsplitter as recited in claim 1, wherein n_z for the first polymer layer is substantially similar to n_z for the second polymer film.

3. A polarizing beamsplitter as recited in claim 2, wherein Δ

n_z/Δ

n_y is less than or equal to 0.1, where Δ

n_z is the mismatch between values of n_z of the first and second layers and Δ

n_y is the mismatch between values of n_y of the first and second layers.

4. A polarizing beamsplitter as recited in claim 1, wherein Δ

n_x/Δ

n_y is less than or equal to 0.05.

5. A polarizing beamsplitter as recited in claim 1, wherein n_x for the first polymer layer is substantially similar to n_x for the second polymer film.

6. A polarizing beamsplitter as recited in claim 5, wherein Δ

n_x/Δ

n_y is less than or equal to 0.1, where Δ

n_x is the mismatch between values of n_y of the first and second layers and Δ

n_y is the mismatch between values of n_y of the first and second layers.

7. A polarizing beamsplitter as recited in claim 6, wherein Δ

n_x/Δ

n_y is less than or equal to 0.01.

8. A polarizing beamsplitter as recited in claim 1, wherein the ratio of transmission of light in the pass polarization state through the polarizing beamsplitter to transmission of light in the blocked polarization state through the polarizing beamsplitter is at least 100 for light incident on the polarizing beamsplitter having an f/number of no more than 2.5.

9. A polarizing beamsplitter as recited in claim 1, wherein the first and second prisms have refractive indices higher than refractive indices of the first and second polymer layers.

10. A polarizing beamsplitter as recited in claim 1, wherein the first polymer layer comprises a polyester.

11. A polarizing beamsplitter as recited in claim 1, wherein the first polymer layer comprises polyethylene naphthalate (PEN).

12. A polarizing beamsplitter as recited in claim 1, wherein the polarizing beamsplitter reflects light having a polarization vector parallel to the y-axis and transmits light having a polarization vector parallel to the x-axis.

13. A polarizing beamsplitter as recited in claim 12, wherein the light propagating through the polarizing beamsplitter is transmitted through the polarization sensitive film.

14. A polarizing beamsplitter as recited in claim 1, wherein the first and second prisms are 45°

prisms with their hypotenuse faces in opposition, the polarization-sensitive film being disposed between the hypotenuse faces, so that the polarization-sensitive film lies at an angle of about 45°

to a normal to the non-hypotenuse faces of the prisms.

15. A polarizing beamsplitter as recited in claim 1, wherein the first and second prisms are glass prisms.

16. A polarizing beamsplitter, comprising:

first and second prisms; and

a multiple layer, polarization-sensitive film disposed between the first and second prisms, the polarization-sensitive film being formed from alternating first and second polymer layers, the polarization-sensitive film having a structural orientation defining x- and y-polarization axes parallel to the film and a z-axis perpendicular to the film, the first polymer layer being birefringent and having a refractive index n_z substantially equal to n_x, where n_x, n_y and n_z are the refractive indices for light having electric field components parallel to the x-axis, y-axis and z-axis respectively, the x-axis defining a transmission polarization state through the polarization-sensitive film, the refractive index for x-polarized light being lower in the polarization-sensitive film than in the first and second prisms.

17. A polarizing beamsplitter as recited in claim 16, wherein n_z for the first polymer layer is substantially similar to n_z for the second polymer film.

18. A polarizing beamsplitter as recited in claim 17, wherein Δ

n_z/Δ

n_y is less than or equal to 0.1, where Δ

n_z is the mismatch between values of n_z of the first and second layers and Δ

n_y the mismatch between values of n_y of the first and second layers.

19. A polarizing beamsplitter as recited in claim 18, wherein Δ

n_x/Δ

n_y is less than or equal to 0.05.

20. A polarizing beamsplitter as recited in claim 16, wherein n_x for the first polymer layer is substantially similar to n_x for the second polymer film.

21. A polarizing beamsplitter as recited in claim 20, wherein Δ

n_x/Δ

n_y is less than or equal to 0.1, where Δ

n_x is the mismatch between values of n_x of the first and second layers and Δ

n_y is the mismatch between values of n_y of the first and second layers.

22. A polarizing beamsplitter as recited in claim 21, wherein Δ

n_x/Δ

n_y is less than or equal to 0.01.

23. A polarizing beamsplitter as recited in claim 16, wherein the ratio of transmission of x-polarized light through the polarizing beamsplitter to transmission y-polarized light through the polarizing beamsplitter is at least 100 for light incident on the polarizing beamsplitter having an f/number of no more than 2.5.

24. A polarizing beamsplitter as recited in claim 16, wherein the first polymer layer comprises a polyester.

25. A polarizing beamsplitter as recited in claim 16, wherein the first polymer layer comprises polyethylene naphthalate (PEN).

26. A polarizing beamsplitter as recited in claim 16, wherein the first and second prisms are 45°

prisms with their hypotenuse faces in opposition, the polarization-sensitive film being disposed between the hypotenuse faces, so that the polarization-sensitive film lies at an angle of about 45°

to a normal to the non-hypotenuse faces of the prisms.