Optical projector and image display apparatus using the same

• US 20050134813A1
• Filed: 08/20/2004
• Published: 06/23/2005
• Est. Priority Date: 12/19/2003
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yoshikawa, Hiroki, Hirata, Koji, Ohishi, Tetsu, Imafuku, Daisuke
• Granted Patent: US 7,261,421 B2
• Time in Patent Office: Days
• US Class Current: 353/122
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G03B 21/005 Projectors using an electronic spatial light modulator but not peculiar thereto

Abstract

Image disturbance called speckle noise occurs when an image generator has a small effective screen size and a projection lens has a small effective diameter. The present invention is intended to reduce speckle noise. In an optical projector, a viewing angle enlarging ember (60) for enlarging viewing angle or a scattering member (28) for scattering image light is disposed near an image display. device (18), such as a liquid crystal panel. Speckle noise can be reduced, suppressing the deterioration of resolution and contrast.

Claims

1. An image display apparatus comprising:

a light source;

an image display device capable of forming an image by modulating light emitted by the light source;

a projection lens for projecting the image formed by the image display device on a screen in an enlarged image; and

a viewing angle enlarging member disposed on either of entrance and exit sides of the image display device or on both the entrance and the exit side of the image display device;

wherein the viewing angle enlarging member corrects image light representing the image formed by the image display device such that viewing angle is enlarged.

2. The image display apparatus according to claim 1, wherein viewing angle enlarging member is a film having different refractive indices with the S-wave and the P-wave.

3. An image display apparatus comprising:

a light source;

an image display device capable of forming an image by modulating light emitted by the light source; and

a projection lens for projecting the image formed by the image display device on a screen in an enlarged image;

wherein the image forming device is a mirror-reflection optical modulator provided with a plurality of reflecting mirrors respectively having roughened surfaces.

4. An image display apparatus comprising:

a light source;

an image display device capable of forming an image by modulating light emitted by the light source;

a projection lens for projecting the image formed by the image display device on a screen in an enlarged image; and

a scattering member disposed in an optical path between the image display device and the projection lens to scatter image light forming the image formed by the image display device.

5. The image display apparatus according to claim 4, wherein the scattering member is placed on the side of an exit surface of the image display device and is bonded to the image display device.

6. The image display apparatus according to claim 4, wherein an optical modulator for modulating the light forming the image formed by the image display device is placed in an optical path between the image display device and the projection lens, and the scattering member is placed on the optical modulator.

7. The image display apparatus according to claim.6, wherein the image display device includes three liquid crystal panels for modulating red, green and blue light beams included in the light emitted by the light source, and the optical modulator is a dichroic prism capable of synthesizing optical images formed by the three liquid crystal panels.

8. An optical projector comprising:

an image display device;

an optical element for projecting an image formed by the image display device in an enlarged image; and

a viewing angle enlarging member disposed near the image display device to enlarge viewing angle.

9. An optical projector comprising;

an image display device; and

an optical element for projecting an image formed by the image display device in an enlarged image;

wherein the image display device is a mirror-reflection optical modulator provided with a plurality of reflecting mirrors respectively having roughened surfaces.

14. The optical projector according to claim 9, wherein the image display device is a transmission liquid crystal panel provided at least with an entrance polarizing plate and an exit polarizing plate serving also as the scattering member on opposite sides thereof, and the exit polarizing plate has a haze value greater than that of the entrance polarizing plate.

10. An optical projector comprising:

an image display device;

an optical element for projecting an image formed by the image display device in an enlarged image; and

a scattering member capable of scattering image light and disposed near the image display device.

11. The optical projector according to claim 10, wherein the image display device is a transmission liquid crystal panel protected at least by an entrance dustproof glass plate and an exit dustproof glass plate serving also as the scattering member, and the exit dustproof glass plate has a haze value greater than that of the entrance dustproof glass plate.

12. The optical projector according to claim 10, wherein the image display device is a transmission liquid crystal panel protected at least by an exit dustproof glass plate serving also as the scattering member, and a diffusive sheet is attached adhesively to a surface of the exit dustproof glass plate.

13. The optical projector according to claim 10, wherein the image display device is a transmission liquid crystal panel provided at least with an exit polarizing plate, and a diffusing plate serving as the scattering member is interposed between the liquid crystal panel and the exit polarizing plate.

15. The optical projector according to claim 10, wherein the optical projector further comprising a dichroic prism,

wherein the image display device includes a plurality of transmission liquid crystal panels capable of forming red, green and blue images by modulating red, green and blue light, the dichroic prism synthesizes the red, the green and the blue image formed by the plurality of transmission liquid crystal panels, and a diffusive sheet as the scattering member is attached adhesively to an entrance surface of the dichroic prism.

16. The optical projector according to claim 10 further comprising a dichroic prism, wherein the image display device includes a plurality of transmission liquid crystal panels capable of forming red, green and blue images by modulating red, green and blue light, the dichroic prism synthesizes the red, the green and the blue image formed by the plurality of transmission liquid crystal panels, and a diffusive sheet as the scattering member is attached adhesively to an exit surface of the dichroic prism.

17. The optical projector according to claim 10, wherein the image display device is a reflection liquid crystal panel protected at least by a dustproof glass plate serving also as the scattering member, and the dustproof glass plate has a haze value greater than those of general dustproof glass plates.

18. The optical projector according to claim 10, wherein the image display device is a reflection liquid crystal panel protected at least by a dustproof glass plate serving also as the scattering member, and the dustproof glass plate has a haze value greater than those of general dustproof glass plate.

19. The optical projector according to claim 10, wherein the image display device is a reflection liquid crystal panel protected at least by a dustproof glass plate, and a diffusive sheet serving as the scattering member is attached adhesively to a surface of the dustproof glass plate.

20. The optical projector according to claim 10, wherein the image display device is a reflection liquid crystal panel provided with at least one beam splitter, and a diffusive sheet serving as the scattering member is attached adhesively to an exit surface of the beam splitter the nearest to the transmission liquid crystal panel.

21. The optical projector according to claim 10, wherein the image display device is a reflection liquid crystal panel provided with at least one beam splitter, and a diffusive sheet serving as the scattering member is attached adhesively to an exit surface of the beam splitter the second nearest to the transmission liquid crystal panel.

22. The optical projector according to claim 10, wherein the image display device is a mirror-reflection optical modulator protected at least by a dustproof glass plate serving also as the scattering member, and the dustproof glass plate has a haze value greater than those of general dustproof glass plates.

23. The optical projector according to claim 10, wherein the image display device is a mirror-reflection optical modulator protected at least by a dustproof glass plate, and a diffusive sheet serving also as the scattering member is attached adhesively to a surface of the dustproof glass plate.

24. The optical projector according to claim 10, wherein the image display device is a mirror-reflection optical modulator protected at least by a dustproof glass plate, and a diffusive plate serving also as the scattering member is interposed between the mirror-reflection optical modulator and a projection lens serving as the optical element.

25. An image display apparatus comprising:

an image display device;

an optical element for projecting an image formed by the image display device in an enlarged image;

a rear projection screen on which the optical element projects the enlarged image; and

a viewing angle enlarging member disposed near the image display device to reduce speckle noise by enlarging viewing angle.

26. An image display apparatus comprising:

an image display device;

an optical element for projecting an image formed by the image display device in an enlarged image;

a rear projection screen on which the optical element projects the enlarged image; and

a scattering member capable of scattering image light to reduce speckle noise and disposed near the image display device.

27. The image display apparatus according to claim 26, wherein the image display device is a transmission liquid crystal panel.

28. The image display apparatus according to claim 26, wherein the image display device is a reflection liquid crystal panel.

29. The image display apparatus according to claim 26, wherein the image display device is a mirror-reflection optical modulator.

30. An image display apparatus comprising:

a light source;

an image display device capable of forming an image by modulating light emitted by the light source;

a projection lens capable of projecting an image formed by the image display device in an enlarged image on a screen; and

a viewing angle compensating film placed on either of entrance side or exit side of the image display device or on both the entrance and the exit sides of the image display device;

wherein the viewing angle compensating film is white and has an oblique light transmitting characteristic effective in reducing speckle noise.