Projection image display apparatus

• US 5,826,959 A
• Filed: 05/07/1997
• Issued: 10/27/1998
• Est. Priority Date: 05/09/1996
• Status: Expired due to Fees

• Current Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Original Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Inventors: Atsuchi, Naruhiko
• Primary Examiner(s): DOWLING, WILLIAM C
• Application Number:
  US08/852,379
• Time in Patent Office: 538 Days
• Field of Search: 353/20, 353/31, 353/33, 353/34, 353/37, 349/5, 349/7, 349/8, 349/9, 349/57
• US Class Current: 353/20
• CPC Class Codes: G02B 27/1026 for use with reflective spatial light modulators
• CPC Class Codes: G02B 27/142 Coating structures, e.g. thin films multilayers
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 27/149 using crossed beamsplitting surfaces, e.g. cross-dichroic cubes or X-cubes
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066
• 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

Abstract

An object of the present invention is to provide a simple image projection apparatus which prevents color shading. First, second and third dichroic mirrors are provided in parallel which separate light from a source into red, blue, and green components. First and second polarization beam splitters are provided with operative surfaces perpendicular to the dichroic mirrors for reflecting predetermined polarization light components of two colors to two reflection type liquid crystal devices. A third polarization beam splitter having an operative surface in parallel to the dichroic mirrors is provided for reflecting a predetermined polarized light component of the third color component to a third reflection type liquid crystal device. A cross dichroic prism device is provided for combining the modulated light from the three liquid crystal devices and transmitting the synthesized light for projection.

Claims

1. A projection image display apparatus comprising:

a light source for generating at least three light components of blue, green and red;

a first dichroic mirror for receiving the light coming from said light source, transmitting said blue light component and reflecting said green and red light components;

a second dichroic mirror, oriented substantially in parallel with said first dichroic mirror, for receiving said green and red light components reflected at said first dichroic mirror and for reflecting said green light component and transmitting said red light component;

a third dichroic mirror, oriented substantially in parallel with said first dichroic mirror, for receiving said blue light components having transmitted through said first dichroic mirror, and for reflecting said blue light component;

a first polarization beam splitter having an operative surface substantially perpendicular to said second dichroic mirror, for reflecting a predetermined polarized light component of said red light component having transmitted through said second dichroic mirror;

a red reflection liquid crystal device for receiving light coming from said first polarization beam splitter and reflecting polarized light with a plane of polarization rotated in accordance with an image signal corresponding to a red color;

a second polarization beam splitter having an operative surface substantially perpendicular to said second dichroic mirror, for reflecting a predetermined polarized light component of said green light component reflected at said second dichroic mirror;

a green reflection liquid crystal device for receiving light coming from said second polarization beam splitter and reflecting polarized light with a plane of polarization rotated in accordance with an image signal corresponding to a green color;

a third polarization beam splitter having an operating surface substantially parallel to said third dichroic mirror, for reflecting a predetermined polarized light component of said blue light component reflected at said third dichroic mirror;

a blue reflection liquid crystal device for receiving light coming from said third polarization beam splitter and reflecting polarized light with a plane of polarization rotated in accordance with an image signal corresponding to a blue color;

a cross prism including a fourth dichroic mirror, oriented substantially perpendicularly to said operative surfaces of said first and second polarization beam splitters and substantially in parallel with said operative surface of said third polarization beam splitter, for reflecting said red light component and transmitting said green and blue light components, and a fifth dichroic mirror, so oriented as to cross said fourth dichroic mirror, for reflecting said blue light component and transmitting said green and red light components, said cross prism synthesizing said red, green and blue light components emitted from said red, green and blue reflection liquid crystal devices and having passed through said first, second and third polarization beam splitters and emitting resultant synthesized light; and

a projection optical system for receiving said synthesized light from said cross prism.

2. The projection image display apparatus according to claim 1, wherein at least one of said second and fourth dichroic mirrors is comprised of a multi-layer film having a plurality of layers of different optical refractive indices stacked in a predetermined order, said multi-layer film including a film having an optical refractive index of approximately 2.5 and a film having an optical refractive index of 1.65 to 1.75.

3. The projection image display apparatus according to claim 2, wherein at least one of said second and fourth dichroic mirrors is comprised of a multi-layer film having at least two layers of different optical refractive indices stacked one on another, said optical refractive index of one layer being approximately 2.50 while said optical refractive index of the other layer is 1.65 to 1.75.

4. The projection image display apparatus according to claim 1, wherein at least one of said second and fourth dichroic mirrors is comprised of a multi-layer film having a plurality of layers of different optical refractive indices stacked in a predetermined order, said multi-layer film including a film having an optical refractive index of approximately 2.35 and a film having an optical refractive index of approximately 1.70.

5. The projection image display apparatus according to claim 4, wherein at least one of said second and fourth dichroic mirrors is comprised of a multi-layer film having at least two layers of different optical refractive indices stacked one on another, said optical refractive index of one layer being approximately 2.35 while said optical refractive index of the other layer is approximately 1.70.

6. The projection image display apparatus according to claim 1, wherein said second dichroic mirror is comprised of a multi-layer film having at least two layers of different optical refractive indices stacked in a predetermined order, and a thickness of said multi-layer film is changed over on operative surface thereof.

7. The projection image display apparatus according to claim 6, wherein said thickness of said multi-layer film is changed over on operative surface thereof in accordance with incident angles of light coming from said first dichroic mirror.

8. The projection image display apparatus according to claim 1, wherein said light source is a metal halide lamp.

9. A projection image display apparatus comprising:

a light source for generating at least three light components of blue, green and red;

a first dichroic mirror for receiving the light coming from said light source, transmitting said red light component and reflecting said green and blue light components;

a second dichroic mirror, oriented substantially in parallel with said first dichroic mirror, for receiving said green and blue light components reflected at said first dichroic mirror and for reflecting said green light component and transmitting said blue light component;

a third dichroic mirror, oriented substantially in parallel with said first dichroic mirror, for receiving said red light components having transmitted through said first dichroic mirror, and for reflecting said red light component;

a first polarization beam splitter having an operative surface substantially perpendicular to said second dichroic mirror, for reflecting a predetermined polarized light component of said blue light component having transmitted through said second dichroic mirror;

a blue reflection liquid crystal device for receiving light coming from said first polarization beam splitter and reflecting polarized light with a plane of polarization rotated in accordance with an image signal corresponding to a blue color;

a second polarization beam splitter having an operative surface substantially perpendicular to said second dichroic mirror, for reflecting a predetermined polarized light component of said green light component reflected at said second dichroic mirror;

a green reflection liquid crystal device for receiving light coming from said second polarization beam splitter and reflecting polarized light with a plane of polarization rotated in accordance with an image signal corresponding to a green color;

a third polarization beam splitter having an operating surface substantially parallel to said third dichroic mirror, for reflecting a predetermined polarized light component of said red light component reflected at said third dichroic mirror;

a red reflection liquid crystal device for receiving light coming from said third polarization beam splitter and reflecting polarized light with a plane of polarization rotated in accordance with an image signal corresponding to a red color;

a cross prism including a fourth dichroic mirror, oriented substantially perpendicularly to said operative surfaces of said first and second polarization beam splitters and substantially in parallel with said operative surface of said third polarization beam splitter, for reflecting said blue light component and transmitting said green and red light components, and a fifth dichroic mirror, so oriented as to cross said fourth dichroic mirror, for reflecting said red light component and transmitting said green and blue light components, said cross prism synthesizing said red, green and blue light components emitted from said red, green and blue reflection liquid crystal devices and having passed through said first, second and third polarization beam splitters and emitting resultant synthesized light; and

a projection optical system for receiving said synthesized light from said cross prism,

wherein said fifth dichroic mirror is comprised of a multi-layer film having a plurality of layers of different optical refractive indices stacked in a predetermined order, a difference between a refractive index of one layer of said multi-layer film and a refractive index of the other layer of said multi-layer film being smaller than 0.90.

10. The projection image display apparatus according to claim 9, wherein a refractive index of one layer of said multi-layer film is substantially 2.50, and a refractive index of the other layer of said multi-layer film is substantially between 1.65 and 1.75.

11. The projection image display apparatus according to claim 9, wherein a refractive index of one layer of said multi-layer film is substantially 2.35, and a refractive index of the other layer of said multi-layer film is substantially 1.70.

12. A projection image display apparatus comprising:

a light source for generating at least three light components of blue, green and red;

a first dichroic mirror for receiving the light coming from said light source, transmitting said red light component and reflecting said green and blue light components;

a second dichroic mirror, oriented substantially in parallel with said first dichroic mirror, for receiving said green and blue light components reflected at said first dichroic mirror and for reflecting said green light component and transmitting said blue light component;

a third dichroic mirror, oriented substantially in parallel with said first dichroic mirror, for receiving said red light components having transmitted through said first dichroic mirror, and for reflecting said red light component;

a first polarization beam splitter having an operative surface substantially perpendicular to said second dichroic mirror, for reflecting a predetermined polarized light component of said blue light component having transmitted through said second dichroic mirror;

a blue reflection liquid crystal device for receiving light coming from said first polarization beam splitter and reflecting polarized light with a plane of polarization rotated in accordance with an image signal corresponding to a blue color;

a second polarization beam splitter having an operative surface substantially perpendicular to said second dichroic mirror, for reflecting a predetermined polarized light component of said green light component reflected at said second dichroic mirror;

a green reflection liquid crystal device for receiving light coming from said second polarization beam splitter and reflecting polarized light with a plane of polarization rotated in accordance with an image signal corresponding to a green color;

a third polarization beam splitter having an operating surface substantially parallel to said third dichroic mirror, for reflecting a predetermined polarized light component of said red light component reflected at said third dichroic mirror;

a red reflection liquid crystal device for receiving light coming from said third polarization beam splitter and reflecting polarized light with a plane of polarization rotated in accordance with an image signal corresponding to a red color;

a cross prism including a fourth dichroic mirror, oriented substantially perpendicularly to said operative surfaces of said first and second polarization beam splitters and substantially in parallel with said operative surface of said third polarization beam splitter, for reflecting said blue light component and transmitting said green and red light components, and a fifth dichroic mirror, so oriented as to cross said fourth dichroic mirror, for reflecting said red light component and transmitting said green and blue light components, said cross prism synthesizing said red, green and blue light components emitted from said red, green and blue reflection liquid crystal devices and having passed through said first, second and third polarization beam splitters and emitting resultant synthesized light; and

a projection optical system for receiving said synthesized light from said cross prism,

wherein said first dichroic mirror is comprised of a multi-layer film having at least two layers stacked in a predetermined order, a thickness of said multi-layer film is changed over on operative surface thereof.

13. The projection image display apparatus according to claim 12, wherein a thickness of said multi-layer film is changed over on operative surface thereof in accordance with an incident angles of the light coming from said light source.