Reflective projection screen and projection system

• US 6,381,068 B1
• Filed: 03/19/1999
• Issued: 04/30/2002
• Est. Priority Date: 03/19/1999
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Ishikawa, Makoto, Nevitt, Timothy J., Takamatsu, Yorinobu, Bruzzone, Charles L., Harada, Takashi, Ouderkirk, Andrew J., Moshrefzadeh, Robert S.
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): LEROUX, ETIENNE PIERRE
• Application Number:
  US09/272,159
• Time in Patent Office: 1,138 Days
• Field of Search: 359/500, 359/492, 359/494, 359/495, 359/452, 359/599, 359/487, 359/485, 359/498, 359/583, 359/584, 359/490, 359/443, 349/87, 349/96, 349/112
• US Class Current: 359/443
• CPC Class Codes: G02B 5/0215 the surface having a regular structure
• CPC Class Codes: G02B 5/0236 the diffusion taking place within the volume of the element
• CPC Class Codes: G02B 5/0257 creating an anisotropic diffusion characteristic, i.e. distributing output differently in two perpendicular axes
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 5/0294 adapted to provide an additional optical effect, e.g. anti-reflection or filter

Abstract

Reflective front projection screens capable of projecting an image with enhanced contrast and a wide viewing angle in the presence of relatively high levels of ambient light are disclosed along with projection systems using the screens. The projection screens include a reflective polarizing element in combination with a diffusing element and/or glare suppressing element. The reflective polarizing element transmits light of one polarization state and reflects light of a different polarization state. The reflective polarizing element may be diffusely reflective or specularly reflective and the optical properties of the diffusing element and/or glare suppressing element may be selected based on the optical properties of the reflective polarizing element to further enhance image brightness and contrast. The projection systems preferably project an image using light of the polarization state that is reflected by the reflective polarizing element in the screen to further enhance brightness and contrast of the image.

Claims

1. A reflective front projection screen having a front surface facing a viewer, the screen comprising:

a specular reflective polarizing element substantially reflecting light having a first polarization state and substantially transmitting light having a second polarization state; and

a diffusing element scattering the light having the first polarization state that is reflected by the reflective polarizing element, the diffusing element located between the reflective polarizing element and the front surface of the screen;

wherein the diffusing element comprises an isotropic diffuser and an anisotropic diffuser.

2. A reflective front projection screen having a front surface facing a viewer, the screen comprising:

a specular reflective polarizing element substantially reflecting light having a first polarization state and substantially transmitting light having a second polarization state;

a diffusing element scattering the light having the first polarization state that is reflected by the reflective polarizing element, the diffusing element located between the reflective polarizing element and the front surface of the screen;

an absorbing element located to absorb substantially all of the light transmitted through the reflective polarizing element; and

a glare suppressing element.

3. A projection screen according to claim 2, wherein the diffusing element is located between the glare suppressing element and the reflective polarizing element.

4. A projection screen according to claim 2, wherein the glare suppressing element comprises an optically rough surface.

5. A projection screen according to claim 2, wherein the absorbing element is opaque.

6. A projection screen according to claim 2, wherein the absorbing element absorbs at least light having the second polarization state.

7. A projection system comprising a projection screen according to claim 2 and an image projector projecting an image using light of the first polarization state.

8. A projection screen according to claim 2, wherein the diffusing element isotropically diffuses light.

9. A projection screen according to claim 2, wherein the diffusing element anisotropically diffuses light.

10. A projection screen according to claim 2, wherein the diffusing element comprises a bulk diffuser.

11. A projection screen according to claim 2, wherein the diffusing element comprises a surface diffuser.

12. A projection screen according to claim 2, wherein the reflective polarizing element comprises first and second materials, at least one of the first and second materials being birefringent, wherein a refractive index difference between the first and second materials for light having the first polarization state is large enough to substantially reflect the light having the first polarization state, and further wherein a refractive index difference between the first and second materials for light having a second polarization orientation is small enough to substantially transmit the light having the second polarization state.

13. A projection screen according to claim 12, wherein the first and second materials are located in alternating layers.

14. A projection screen according to claim 2, wherein the reflective polarizing element comprises a cholesteric reflective polarizer.

15. A reflective front projection screen having a front surface facing a viewer, the screen comprising:

a diffuse reflective polarizing element substantially reflecting light having a first polarization state and substantially transmitting light having a second polarization state; and

a glare suppressing element suppressing specular glare from the diffuse reflective polarizing element, the glare suppressing element located between the diffuse reflective polarizing element and the front surface of the screen.

16. A projection screen according to claim 15, wherein the diffuse reflective polarizing element diffuses the reflected light isotropically.

17. A projection screen according to claim 15, wherein the diffuse reflective polarizing element diffuses the reflected light anisotropically.

18. A projection screen according to claim 15, wherein the glare suppressing element anisotropically scatters light.

19. A projection screen according to claim 15, wherein the glare suppressing element isotropically scatters light.

20. A projection screen according to claim 15, wherein the reflective polarizing element comprises first and second materials, at least one of the first and second materials being birefringent, wherein a refractive index difference between the first and second materials for light having the first polarization state is large enough to substantially reflect the light having the first polarization state, and further wherein a refractive index difference between the first and second materials for light having a second polarization orientation is small enough to substantially transmit the light having the second polarization state.

21. A projection screen according to claim 20, wherein the second material is disposed within the first material of the polarizing element.

22. A projection screen according to claim 21, wherein the second material comprises elongated bodies aligned along a first axis within the first material of the polarizing element.

23. A projection screen according to claim 15, further comprising a diffusing element.

24. A projection screen according to claim 23, wherein the diffuse reflective polarizing element diffuses light anisotropically and the diffusing element diffuses light isotropically.

25. A projection screen according to claim 23, wherein the diffuse reflective polarizing element diffuses light anisotropically and the diffusing element diffuses light anisotropically.

26. A projection screen according to claim 23, wherein the diffuse reflective polarizing element diffuses light isotropically and the diffusing element diffuses light isotropically.

27. A projection screen according to claim 23, wherein the diffuse reflective polarizing element diffuses light isotropically and the diffusing element diffuses light anisotropically.

28. A projection screen according to claim 15, further comprising an absorbing element located to absorb substantially all of the light transmitted through the reflective polarizing element.

29. A projection screen according to claim 28, wherein the absorbing element is opaque.

30. A projection system comprising a projection screen according to claim 15 and an image projecting an image using light of the first polarization state.