Projection apparatus

• US 20060103810A1
• Filed: 11/12/2004
• Published: 05/18/2006
• Est. Priority Date: 11/12/2004
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Hebrink, Timothy J., Bruzzone, Charles L., Ma, Jiaying, Li, Fuming B., Merrill, William W., Aastuen, David J., Johnson, Harry E.
• Granted Patent: US 7,261,418 B2
• Time in Patent Office: Days
• US Class Current: 353/20
• CPC Class Codes: G02B 27/1026 for use with reflective spatial light modulators
• CPC Class Codes: G02B 27/1073 characterized by manufacturing or alignment methods
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• 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 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20

Abstract

A projection engine uses a first polarizing beam splitter (PBS) that substantially reflects light incident along a first input direction in a first polarization state and substantially transmits light incident in the first input direction in a second polarization state orthogonal to the first polarization state. The first PBS demonstrates an angularly dependent reflectivity for light in the second polarization state that is asymmetric about the first input direction. At least two imager devices are positioned to receive light reflected and transmitted by the first PBS respectively. The imager devices modulate the incident light with an image. The image light from the imagers is combined and projected.

Claims

1. A projection engine device, comprising:

a first polarizing beam splitter (PBS), the first PBS for substantially reflecting light incident along a first input direction in a first polarization state and substantially transmitting light incident in the first input direction in a second polarization state orthogonal to the first polarization state, the first PBS demonstrating an angularly dependent reflectivity for light in the second polarization state that is asymmetric about the first input direction;

a second PBS positioned to receive light reflected by the first PBS;

a third PBS positioned to receive light transmitted through the first PBS;

a first imaging element configured and arranged to a) receive, as first incident light, at least a first portion of the light received by the second PBS from the first PBS;

b) polarization modulate at least a portion of the first incident light from the first polarization state to the second polarization state or from the second polarization state to the first polarization state; and

c) reflect the polarization modulated light back to the second PBS as first image light;

a second imaging element configured and arranged to a) receive, as second incident light, at least a first portion of the light received by the third PBS from the first PBS;

b) polarization modulate at least a portion of the second incident light from the first polarization state to the second polarization state or from the second polarization state to the first polarization state; and

c) reflect the polarization modulated light back to the third PBS as second image light; and

a combiner positioned to receive the first and second image light from the second and third PBSs, respectively.

2. The device of claim 1, wherein the reflectivity for light in the second polarization state is substantially flat as a function of incident angle for angles of incidence up to at least 5°

on one side of the first input direction.

3. The device of claim 1, wherein the light reflected by the first PBS is incident generally on the second PBS along a second input direction and the second PBS demonstrates an angularly dependent reflectivity for light in the second polarization that is asymmetric about the second input direction.

4. The device of claim 3, wherein the reflectivity for light in the second polarization state is substantially flat as a function of incident angle for angles of incidence up to at least 5°

on one side of the second input direction.

5. The device of claim 3, wherein off-axis light in the second polarization state is incident on the first PBS at a first off-axis angle and is incident on the second PBS at a second off-axis angle, the reflectivity for the light in the second polarization state being higher for incidence on the first PBS at the first off-axis angle than for incidence on the second PBS at the second off-axis angle.

6. The device of claim 3, wherein off-axis light in the second polarization state is incident on the first PBS at a first off-axis angle and is incident on the second PBS at a second off-axis angle, the reflectivity for the light in the second polarization state being lower for incidence on the first PBS at the first off-axis angle than for incidence on the second PBS at the second off-axis angle.

7. The device of claim 1, wherein the first PBS is a Cartesian PBS.

8. The device of claim 7, wherein the first PBS comprises two covers and a multilayer polymeric film disposed between the two covers, the multilayer polymeric film being polarization sensitive.

9. The device of claim 8, wherein the multilayer polymeric film comprises a plurality of layers comprising a polyester comprising terephthalate monomer units.

10. The device of claim 9, wherein the multilayer polymeric film comprises alternating layers of first and second polymeric materials, the layer of first polymeric material being birefringent with a first in-plane refractive index, corresponding to a first in-plane direction, being different from a second in-plane refractive index, a difference between the first in-plane refractive index and a thickness refractive index being less than the difference between the second in-plane refractive index and the thickness refractive index.

11. The device of claim 10, wherein light in the second polarization state entering the first PBS along the input direction experiences an effective refractive index in the first layer of polymeric material arising from the second in-plane refractive index and the thickness refractive index, a magnitude of a difference between the effective refractive index and a refractive index of the second layer of polymeric material experienced by the light in the second polarization state being less than 0.01.

12. The device of claim 11, wherein the difference is less than 0.004.

13. The device of claim 12, wherein the difference is less than 0.002.

14. The device of claim 10, wherein the sign of the difference between the second in-plane refractive index of the first layer of polymeric material and the second-in-plane refractive index of the second layer of polymeric material at a wavelength above about 600 nm is different from the sign of the difference between the second in-plane refractive index of the first layer of polymeric material and the second-in-plane refractive index of the second layer of polymeric material at a wavelength below about 450 nm.

15. The device of claim 9, wherein the polyester comprises a homopolymer or copolymer of ethylene terephthalate.

16. The device of claim 8, wherein first PBS comprises two multilayer polymeric films disposed between the two covers.

17. The device of claim 7, wherein the second PBS is a Cartesian PBS.

18. The device of claim 17, wherein the second PBS comprises two covers and a multilayer polymeric film disposed between the two covers, the multilayer polymeric film being polarization sensitive.

19. The device of claim 18, wherein the multilayer polymeric film comprises a plurality of layers comprising a polyester comprising naphthalate monomer units.

20. The device of claim 19, wherein the polyester comprises a homopolymer or copolymer of ethylene naphthalate.

21. The device of claim 1, further comprising a third imaging element configured and arranged to a) receive, as third incident light, at least a second portion of the light received by the third PBS from the first PBS, light in the third incident light being in a color band different from a color band of the second incident light;

b) polarization modulate at least a portion of the third incident light from the first polarization state to the second polarization state or from the second polarization state to the first polarization state; and

c) reflect the polarization modulated light back to the third PBS as third image light.

22. The device of claim 1, further comprising a third imaging element configured and arranged to a) receive, as third incident light, at least a second portion of the light received by the second PBS from the first PBS, light in the third incident light being in a color band different from a color band of the first incident light;

b) polarization modulate at least a portion of the third incident light from the first polarization state to the second polarization state or from the second polarization state to the first polarization state; and

c) reflect the polarization modulated light back to the third PBS as third image light.

23. The device of claim 1, wherein the first PBS reflects less than 5% of light in the second polarization state when illuminated by light in the wavelength range from about 430 nm to about 700 nm and having an f-number of no more than f/2.5.

24. The device of claim 23, wherein the first PBS reflects at least 99% of light in the first polarization state when illuminated by light in the wavelength range from about 430 nm to about 700 nm and having an f-number of no more than f/2.5.

25. A projection engine device, comprising:

a first polarizing beam splitter (PBS), the first PBS for substantially reflecting light incident along a first input direction in a first polarization state and substantially transmitting light incident in the first input direction in a second polarization state orthogonal to the first polarization state, the first PBS demonstrating an angularly dependent reflectivity for light in the second polarization state that is asymmetric about the first input direction;

at least a first imaging device configured and arranged to impose an image on light reflected by the first PBS;

at least a second imaging device configured and arranged to impose an image on light transmitted through the first PBS; and

a combining element disposed to combine image light received from the at least a first imaging device and the at least a second imaging device to form a combined image beam.

26. A device as recited in claim 25, further comprising a second PBS disposed to reflect light reflected by the first PBS to the first imaging device.

27. A device as recited in claim 26, wherein the light reflected from the first PBS to the second PBS reaches the second PBS propagating generally along a second input direction, the second PBS having an angularly dependent reflectivity for light in the second polarization state that is asymmetric about the second input direction.

28. A device as recited in claim 25, further comprising a third PBS disposed to receive light transmitted through the first PBS, wherein the at least a second imaging device comprises a second and a third imaging device, the second imaging device receiving light reflected by the third PBS and the third imaging device receiving light transmitted through the third PBS.

29. A device as recited in claim 28, wherein the light transmitted through the first PBS comprises light in at least first and second color bands, and further comprising a first polarization rotating element disposed between the first and third PBSs to rotate polarization of light in at least the first color band.

30. A device as recited in claim 29, further comprising a second polarization rotating element disposed between the third PBS and the combining element, the second polarization element rotating polarization of image light in one of the first and second color bands received from the third PBS.

31. A device as recited in claim 25, further comprising a light source capable of producing illumination light incident at the first PBS, along the first input direction.

32. A device as recited in claim 25, further comprising a projection lens unit disposed to project the combined image light from the combining element.

33. An optical body, comprising:

at least one layer of a polyethylene terephthalate (PET) copolymer, the PET copolymer being formed from monomers comprising cyclohexanedimethanol, dimethylcyclohexanedicarboxylate, dimethylterephthalate, neopentyl glycol and trimethylol propane, the PET copolymer also comprising less than about 0.0171 percent weight of cobalt acetate.

34. An optical body as recited in claim 33, wherein the cobalt acetate is present in the PET copolymer in an amount of at least about 0.0123 percent weight.