Liquid crystal projector

• US 4,770,525 A
• Filed: 03/12/1987
• Issued: 09/13/1988
• Est. Priority Date: 03/24/1986
• Status: Expired due to Term

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Ogawa, Masahiro, Umeda, Osamu, Shimazaki, Tatsuo
• Primary Examiner(s): HAROIAN, HARRY
• Application Number:
  US07/025,019
• Time in Patent Office: 551 Days
• Field of Search: 353/84, 353/85, 353/86, 353/87, 353/120, 353/121, 353/102, 353/38, 353/102, 353/95, 353/22, 353/23, 353/122, 350/452
• US Class Current: 353/122
• CPC Class Codes: G02F 1/133526 Lenses, e.g. microlenses or Fresnel lenses
• CPC Class Codes: G03B 21/006 using LCD's

Abstract

In a liquid crystal projector wherein a light source is arranged behind a transmission liquid crystal display panel having a rectangular display portion, an image displayed on the liquid crystal display panel is enlarged by a projection lens, and an enlarged image is projected on the screen located in front of the liquid crystal display panel, a linear Fresnel lens is arranged between the light source and the liquid crystal display panel to narrow illumination light beam from the light source along only the widthwise direction of the rectangular display portion. When the illumination light beam from the light source is narrowed along only the widthwise direction of panel, the amount of unused light beam emitted outside the long sides of the display portion can be reduced, and the light beam from the light source can be effectively utilized for image projection.

Claims

1. A liquid crystal projector comprising:

a light source;

a transmission liquid crystal display panel irradiated with a light beam from said light source and having a rectangular display portion;

a projection lens, arranged on a line extending from an optical axis obtained by connecting said light source and said liquid crystal display panel, for enlarging an image displayed on said liquid crystal panel onto a screen; and

optical means, arranged between said light source and said liquid crystal display panel, for narrowing the light beam along a widthwise direction of said rectangular display portion of said liquid crystal display panel, wherein said optical means comprises an eccentric linear Fresnel lens, the center of which is deviated from the optical axis of said light source by a predetermined distance.

2. A projector according to claim 1, wherein said liquid crystal display panel (1) has primary-color filters (RF, GF, BF) shaped like a stripe, arranged side by side, and extending in a direction in which the light beam is narrowed by said optical means.

3. A liquid crystal projector comprising:

a light source;

a transmission liquid crystal display panel irradiated with light from said light source and having a rectangular display portion;

a projection lens, arranged on a line extending from an optical axis obtained by connecting said light source and said liquid crystal display panel, for enlarging an image displayed on said liquid crystal display panel onto a screen; and

optical means, arranged between said light source and said liquid crystal display panel, for narrowing the light from said light source along a widthwise direction of said rectangular display portion of said liquid crystal display panel and for correcting narrowed light into light parallel to the optical axis, wherein said optical means comprises a first linear Fresnel lens for narrowing the light from said light source along a widthwise direction of said rectangular display portion of said liquid crystal display panel, and a second linear Fresnel lens for correcting the light narrowed by said first Fresnel lens into light parallel to the optical axis of said light source.

4. A projector according to claim 3, wherein said first linear Fresnel lens has a convex lens function and said second linear Fresnel lens has a concave lens function.

5. A projector according to claim 4, wherein a distance between said first and second linear Fresnel lenses is sufficiently shorter than a focal length of said first linear Fresnel lens.

6. A projector according to claim 3, wherein said first and second linear Fresnel lenses respectively have convex lens functions, said second linear Fresnel lens being spaced apart from said first linear Fresnel lens by a focal length of said first linear Fresnel lens in such a manner that a lens surface of said second linear Fresnel lens is directed toward said first linear Fresnel lens.

7. A liquid crystal projector comprising:

a light source;

a transmission liquid crystal display panel irradiated with light from said light source, a width of the light from said light source being sufficiently larger than that of a display portion of said liquid crystal display panel;

a projection lens, arranged on a line extending from an optical axis obtained by connecting said light source and said liquid crystal display panel, for enlarging an image displayed on said liquid crystal panel onto a screen;

lens means, arranged between said light source and said liquid crystal display panel, for narrowing outer beams of the light from said light source in a inward direction of said display portion of said liquid crystal display panel; and

lens means for correcting the light narrowed by said narrowing lens means into beams parallel to the optical axis extending toward said liquid crystal display panel, wherein said correcting lens means comprises a central flat surface portion having no lens function, the central beams of the light passing through said narrowing lens means being adapted to propagate straight through said central flat surface portion, and peripheral annular concave lens portions for receiving the outer beams focused by said narrowing lens means.

8. A projector according to claim 7, wherein said narrowing lens means comprises a central flat surface portion having no lens function, the central beams of the light from said light source being adapted to propagate straight through said central flat surface portion, and peripheral annular convex lens portions continguous with said central flat surface portion.

9. A projector according to claim 8, wherein said correcting lens means is located at a position where the outer beams focused by said narrowing lens means cross the central beams passing through said flat surface portion of said narrowing lens means.

10. A liquid crystal projector comprising:

a light source;

a transmission liquid crystal display panel irradiated with a light beam from said light source and having a rectangular display portion;

a projection lens, arranged on a line extending from an optical axis obtained by connecting said light source and said liquid crystal display panel, for enlarging an image displayed on said liquid crystal panel onto a screen; and

optical means, arranged between said light source and said liquid crystal display panel, for narrowing the light beam along a widthwise direction of said rectangular display portion of said liquid crystal display panel, wherein said liquid crystal display panel has primary-color filters shaped like a stripe, arranged side by side, and extending in a direction in which the light beam is narrowed by said optical means.