Optical projector and image display apparatus using the same

• US 7,261,421 B2
• Filed: 08/20/2004
• Issued: 08/28/2007
• 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
• Primary Examiner(s): Dowling; William C.
• Application Number:
  US10/922,706
• Publication Number:
  US 20050134813A1
• Time in Patent Office: 1,103 Days
• Field of Search: 353/20, 353/31, 353/33, 353/34, 353/37, 353/122, 349/5, 349/7, 349/8, 349/9, 359/64, 359/112
• US Class Current: 353/31
• 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 including a separate image display element for modulating each of red, green and blue light emitted by the light source along respective optical paths;

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

a scattering member disposed in the optical path between each of the image display elements and the projection lens to scatter light from each of the image display elements forming the image;

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 scattering member is positioned on a dichroic prism which is disposed in each optical path between each of the three liquid crystal panels and the projection lens for synthesizing optical images formed by the three liquid crystal panels.

2. The image display apparatus according to claim 1 wherein the scattering member is bonded to an entrance surface of the dichroic prism.

3. The image display apparatus according to claim 1 wherein the scattering member is bonded to an exit surface of the dichroic prism.

4. An optical projector comprising:

an image display device including three image display elements for modulating each of red, green and blue light emitted by a light source along respective optical paths;

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

a scattering member disposed in the optical path between each of the three image display elements and the optical element to scatter light forming the image;

wherein the scattering member is positioned on a dichroic prism which is disposed in each optical path between each of the three image display elements and the optical element for synthesizing optical images formed by the three image display elements.

5. The optical projector according to claim 4 further comprising:

a dichroic prism; and

a diffusive sheet providing the scattering member attached to each entrance surface of the 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; and

wherein the dichroic prism synthesizes the red, the green and the blue image formed by the plurality of transmission liquid crystal panels.

6. An optical projector comprising:

an image display device including three transmission liquid crystal panels for modulating each of red, green and blue light emitted by a light source along respective optical paths;

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

a scattering member disposed in the optical path between each of the three transmission liquid crystal panels and the optical element to scatter light forming the image,

wherein the three transmission liquid crystal panels are protected at least by an entrance dustproof glass plate and an exit dustproof glass plate serving also as the scattering member, and wherein the exit dustproof glass plate has a haze value greater than the haze value of the entrance dustproof glass plate.

7. An optical projector comprising:

an image display device including three transmission liquid crystal panels for modulating each of red, green and blue light emitted by a light source along respective optical paths;

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

a scattering member disposed in the optical path between each of the three transmission liquid crystal panels and the optical element to scatter light forming the image,

wherein the three transmission liquid crystal panels are protected at least by an exit dustproof glass plate also functioning as the scattering member, and a diffusive sheet is attached adhesively to a surface of the exit dustproof glass plate.

8. An optical projector comprising:

an image display device including three transmission liquid crystal panels for modulating each of red, green and blue light emitted by a light source along respective optical paths;

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

a scattering member disposed in the optical path between each of the three transmission liquid crystal panels and the optical element to scatter light forming the image,

wherein the image display device has three exit polarizing plates, and the scattering member is provided by a diffusing plate interposed between each of the three transmission liquid crystal panels and each of the three exit polarizing plates.

9. An optical projector comprising:

an image display device including for modulating each of red, green and blue light emitted by a light source along respective optical paths;

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

a scattering member disposed in the optical path between each of the three image display elements and the optical element to scatter light forming the image, a dichroic prism;

a diffusive sheet providing the scattering member is attached adhesively to an exit surface of the 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; and

wherein the dichroic prism synthesizes the red image, the green image and the blue image formed by the plurality of transmission liquid crystal panels.

10. An optical projector comprising:

an image display device including three reflection liquid crystal panels for modulating each of red, green and blue light emitted by a light source along respective optical paths;

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

a scattering member disposed in the optical path between each of the three reflection liquid crystal panels and the optical element to scatter light forming the image,

wherein the three reflection liquid crystal panels are protected at least by a dustproof glass plate serving also as the scattering member.

11. An optical projector comprising:

an image display device including three reflection liquid crystal panels for modulating each of red, green and blue light emitted by a light source along respective optical paths;

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

a scattering member disposed in the optical path between each of the three reflection liquid crystal panels and the optical element to scatter light forming the image,

wherein the three reflection liquid crystal panels are 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.

12. The optical projector according to claim 11, wherein the image display device comprises the three reflection liquid crystal panels provided with plural beam splitters, and a diffusive sheet serving as the scattering member is attached adhesively to at least one exit surface of the plural beam splitter nearest to the reflection liquid crystal panel.

13. An optical projector comprising:

an image display device including a reflection liquid crystal panel for modulating each of red, green and blue light emitted by a light source along respective optical paths;

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

a scattering member disposed in the optical path between the reflection liquid crystal panel and the optical element to scatter light forming the image, wherein the image display device comprises a mirror-reflection optical modulator protected at least by a dustproof glass plate serving also as the scattering member.

14. An optical projector comprising:

an image display device including a reflection liquid crystal panel for modulating each of red, green and blue light emitted by a light source along respective optical paths;

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

a scattering member disposed in the optical path between the reflection liquid crystal panel and the optical element to scatter light forming the image, wherein the image display device comprises 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.

15. An optical projector comprising:

an image display device including a reflection liquid crystal panel for modulating each of red, green and blue light emitted by a light source along respective optical paths;

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

a scattering member disposed in the optical path between the reflection liquid crystal panel and the optical element to scatter light forming the image, wherein the image display device comprises 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.

16. An image display apparatus comprising:

an image display device;

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

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

a scattering member capable of scattering image light to reduce speckle noise which member is disposed near the image display device;

wherein the image display device includes three liquid crystal panels for modulating red, green and blue light beams included in the light emitted by a light source, and the scattering member is positioned on a dichroic prism which is disposed in each optical path between each of the three liquid crystal panels and the optical element for synthesizing optical images formed by the three liquid crystal panels.

17. The image display apparatus according to claim 16 wherein the image display device comprises a transmission liquid crystal panel.

18. The image display apparatus according to claim 16 wherein the image display device comprises a reflection liquid crystal panel.

19. The image display apparatus according to claim 16 wherein the image display device comprises a mirror reflection optical modulator.