Liquid crystal projector

• US 5,097,323 A
• Filed: 10/19/1989
• Issued: 03/17/1992
• Est. Priority Date: 01/25/1988
• Status: Expired due to Term

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Ogawa, Masahiro, Nakamura, Hideki, Sato, Makoto, Shimazaki, Tatsuo
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Metjahic, Safet
• Application Number:
  US07/424,128
• Time in Patent Office: 880 Days
• Field of Search: 358/60-63, 358/230-231, 350/331 R, 350/171-174, 350/345, 350/401-403, 350/394, 350/397, 350/398, 350/452, 350/445, 353/31, 353/34
• US Class Current: 348/761
• 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 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28
• CPC Class Codes: H04N 9/3176 wherein the projection device is incorporated in a camera details of cameras adapted for combination with a projector not peculiar to the presence of an electronic spatial light modulator G03B17/54

Abstract

A liquid crystal projector of the type, wherein the light emitted from a light source is split into a red beam, a green beam, and a blue beam, and these beams are applied to red-image, green-image, and blue-image display LCD panels, the red-image beam, the green-image beam, and the blue-image beam emerging from these LCD panels are combined and projected by a projection lens, thereby to form a full-color image. The projector has an optical system which guides the beams such that these beam have optical paths of the same length which extend from the light source or the LCD panels to the projection lens.

Claims

1. A liquid crystal projector, comprising:

light source means;

first to third liquid crystal panels;

a projection lens;

optical means for splitting light emitted from said light source means into three beams of primary colors, and for guiding the three beams to said projection lens via said first to third liquid crystal panels, respectively, along three optical paths having substantially equal length;

wherein said optical means includes a plurality of dichroic mirrors and a plurality of mirrors; and

wherein said dichroic mirrors and said mirrors are arranged three-dimensionally.

2. A liquid crystal projector, comprising:

light source means;

first to third liquid crystal panels;

a projection lens;

optical means for splitting light emitted from said light source means into three beams of primary colors, and for guiding the three beams to said projection lens via said first to third liquid crystal panels, respectively, along three optical paths having substantially equal length; and

wherein said optical means includes a mirror having two total-reflection light-reflecting surfaces, one of which is arranged to reflect a beam of a primary color and the other of which is arranged to reflect a beam of another primary color.

3. A liquid crystal projector, comprising:

light source means;

first to third liquid crystal panels;

a projection lens;

optical means for splitting light emitted from said light source means into three beams of primary colors, and for guiding the three beams to said projection lens via said first to third liquid crystal panels, respectively, along three optical paths having substantially equal length; and

wherein said optical means includes;

a first dichoric mirror for transmitting a first color beam emitted from said light source means, and reflecting the beams of second and third color beams;

a first mirror for reflecting the beams of the second and third color beams reflected by said first dichoric mirror and applying these beams in a direction parallel to, and the same as, the first color beam transmitted through said first dichoric mirror;

a second dichoric mirror for transmitting the second color beam reflected by said first mirror, and reflecting the third color beams in a direction parallel to, and opposite to, the second and third color beams reflected by said first dichroic mirror;

a second mirror for reflecting the first color beam transmitted through said first dichroic mirror and applying this beam in the same direction as the third color beam reflected by said second dichroic mirror;

a third mirror for reflecting the first color beam reflected by said second mirror and applying this beam in direction parallel to, and the same as, the first color beam transmitted through said first dichroic mirror;

a fourth mirror for reflecting the first color beam reflected by said third mirror and applying this beam in a direction parallel to, and opposite to, the first color beam reflected by said second mirror;

a fifth mirror for reflecting the second color beam transmitted through said second dichroic mirror and applying this beam in a direction parallel to, and the same as, the third color beam reflected by said second dichroic mirror;

a sixth mirror for reflecting the third color beam reflected by said second dichroic mirror and applying this beam in the same direction as the first color beam transmitted through said first dichroic mirror; and

a dichroic prism for superposing the first, second and third color beams which are transmitted through said first to third liquid crystal panels, respectively, and thereby outputting a full-color image beam.

4. A liquid crystal display apparatus comprising:

light source means;

first to third liquid crystal panels;

first optical means for applying light emitted from said light source means, to said first to third liquid crystal panels;

second optical means for projecting light beams emerging from said first to third liquid crystal panels;

third optical means for guiding beams emerging from said first to third liquid crystal panels, such that these beams have optical paths of substantially equal length; and

wherein said third optical means includes two convex lenses; and

wherein said two convex lenses are located such that their focal points coincide.

5. A liquid crystal projector comprising:

light source means;

first to third liquid crystal panels;

first optical means for applying light emitted from said light source means, to said first to third liquid crystal panels;

second optical means including a projection lens for projecting three light beams emitted from said first to third liquid crystal panels; and

third optical means for guiding beams emerging from said first to third liquid crystal panels, such that these beams have substantially equal luminance when reaching said projection lens;

wherein said third optical means includes two convex lenses; and

wherein said two convex lenses are located such that their focal points coincide.

6. A liquid crystal projector comprising:

light source means;

first to third liquid crystal panels;

first optical means for applying light emitted from said light source means, to said first to third liquid crystal panels;

second optical means including a projection lens for projecting three light beams emitted from said first to third liquid crystal panels; and

third optical means for guiding beams emerging from said first to third liquid crystal panels, such that these beams have substantially equal luminance when reaching said projection lens;

wherein said third optical means is a light-transmitting member; and

wherein said light-transmitting member has a refractive index n which satisfies the following equation;

space="preserve" listing-type="equation">L=(1-n'"'"'/n)d

where L is the difference between the length of the longer optical paths of two of the three beams and that of the shorter optical path of the remaining beam, n'"'"' is the refractive index of air, and d is the width of said light-transmitting member as measured in the direction in which the beams pass through said light-transmitting member.

7. A liquid crystal display apparatus comprising:

liquid crystal projector comprising;

light source means;

first to third liquid crystal panels;

first optical means for applying light emitted from said light source means, to said first to third liquid crystal panels;

second optical means for projecting light beams emerging from said first to third liquid crystal panels;

third optical means for guiding beams emerging from said first to third liquid crystal panels, such that at least one of the three beams having a longer optical path is less diverged than at least one of the remaining beams having a shorter optical path;

wherein said third optical means is a light-transmitting member; and

wherein said light-transmitting member has a refractive index n which satisfies the following equation;

space="preserve" listing-type="equation">L=(1-n'"'"'/n)d

where L is the difference between the length of the longer optical paths of two of the three beams and that of the shorter optical path of the remaining beam, n'"'"' is the refractive index of air, and d is the width of said light-transmitting member as measured in the direction in which the beams pass through said light-transmitting member.

8. A liquid crystal projector comprising:

light source means;

liquid-crystal display panel means having a plurality of image-display sections for receiving the light emitted from said light source means and outputting image beams;

a projection lens for projecting the image beams supplied from said liquid-crystal display panel means;

first mirror means located on the light-receiving side of said projection lens, for reflecting the image beam supplied from the first image-display section and applying this image beam toward said projection lens;

second mirror means located between said first mirror means and said projection lens, for reflecting the image beam supplied from the second image-display section and applying this beam toward said projection lens, and for passing the image beam reflected by said first mirror means;

third mirror means for reflecting at least one of the two image beams to be guided to said first and second mirror means, respectively; and

means locating said first to third mirror means such that the image beams have optical paths of the same length which extend from said image-display sections to said projection lens.

9. A liquid crystal projector comprising:

light source means;

first to third liquid crystal panels;

a projection lens; and

optical means for splitting light emitted from said light source means into three beams of primary colors, and guiding the three beams to said projection lens via said first to third liquid crystal panels;

wherein said optical means includes a mirror having two total-reflection light-reflecting surfaces, one of which is arranged to reflect a beam of a primary color and the other of which is arranged to reflect a beam of another primary color.