Projection display system

• US 5,662,400 A
• Filed: 09/29/1995
• Issued: 09/02/1997
• Est. Priority Date: 04/20/1992
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation), Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Kida, Hiroshi, Daijogo, Akira, Shikama, Shinsuke
• Primary Examiner(s): DOWLING, WILLIAM C
• Application Number:
  US08/536,355
• Time in Patent Office: 704 Days
• Field of Search: 353/31, 353/33, 353/34, 353/37, 353/20, 353/102, 359/487, 359/488, 359/495, 359/496, 359/497, 359/48, 359/49, 359/50, 359/63
• US Class Current: 353/31
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0047 for use with a light source G02B19/009, G02B19/0095 take precedence; details of lighting devices in general F21V; non-semiconductor lasers having optical devices external to the laser cavity H01S3/005
• CPC Class Codes: G02B 3/04 with continuous faces that are rotationally symmetrical but deviate from a true sphere , e.g. so called "aspheric" lenses
• CPC Class Codes: G02B 5/3066 involving the reflection of light at a particular angle of incidence, e.g. Brewster's angle
• 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 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

Disclosed is a condenser lens with large aperture, having a numerical aperture of 0.9 or larger, which consists of a bi-aspherical single lens having a first surface of convex form facing the larger conjugate side and a second surface facing the smaller conjugate side and whose outermost circular zone is formed concave, the condenser lens satisfying the following conditions (1) or (2). Also disclosed are a light source apparatus using such a condenser lens and a projection display apparatus using such a light source apparatus.

(1) 0.42<r1/nf<0.45 18<|r2/nf| -0.39<K1<-0.25 0.11<Δ2/f<0.14

(2) 0.4<r1/nf<0.6 -0.5<r2/nf<-0.3 -0.6<K1<-0.2 -0.1<SG2/f<0.1

where

f: focal length of the whole lens system

n: refractive index of the lens

r1: radius of center curvature of the first surface

r2: radius of center curvature of the second surface

K1: conic constant of the first surface

Δ2: axial difference between the aspherical face of the outermost circular zone within the effective diameter of the second surface and a reference spherical face having the radius of center curvature of r2.

SG2: axial difference of the aspherical face of the outermost circular zone within the effective diameter of the second surface with respect to the center of the second surface.

Claims

1. A projection display apparatus comprising:

a pair of discharge electrodes with a center of emission disposed therebetween,

a spherical mirror having a center of curvature substantially corresponding to the center of emission,

a condenser lens having a focal point substantially corresponding to the center of emission wherein the discharge electrodes emit light along an optical axis which is reflected by the spherical mirror and refracted by the condenser lens;

a rectangular image display device receiving the refracted light from said condenser lens, wherein a longitudinal direction of said discharge electrodes is aligned parallel to a direction in which a shorter side of the rectangular display device extends; and

a projection lens for enlarging and projecting an image formed on said image display-device.

2. A projection display apparatus according to claim 1, wherein the discharge electrodes are part of a discharge lamp and

a posture of the discharge lamp is arranged with respect to the discharge electrodes such that an exhaust vent formed in the discharge lamp faces a direction perpendicular to a direction in which the optical axis of the light extends.

3. A projection display apparatus comprising:

a pair of discharge electrodes with a center of emission disposed therebetween emitting light along an optical axis;

an exhaust vent, formed during manufacture of a discharge lamp containing said discharge electrodes, arranged such that said exhaust vent faces a direction perpendicular to the direction in which the optical axis of the light extends;

a spherical mirror having a center of curvature substantially corresponding to the center of emission;

a condenser lens having a focal point substantially corresponding to the center of emission wherein the discharge electrodes emit light which is reflected by the spherical mirror and refracted by the condenser lens;

a rectangular image display device receiving the refracted light from said condenser lens; and

a projection lens for enlarging and projecting an image formed on said image display device.

4. A projection display apparatus according to claim 3, wherein

the display screen of the image display device is rectangular in shape, and the discharge electrodes are aligned with the extending direction of the shorter sides of the display screen.

5. A projection display apparatus comprising:

a light source device including a lamp for emitting white light and a condenser lens receiving the white light, said condenser lens having a chromatic aberration causing the white light to have a diverging light portion and a converging light portion at an output of said condenser lens;

color separating means for separating the white light emitted from said light source device into red light, green light, and blue light;

a convex lens receiving the diverging light portion and correcting for divergence of the diverging light portion caused by said condenser lens;

a concave lens receiving the converging light portion and correcting for convergence of the converging light portion caused by said condenser lens;

image display devices illuminated by the red light, green light and blue light including the corrected diverging light portion and corrected converging light portion, and forming a red image, a green image, and a blue image, respectively;

color combining means for combining the red image, green image and blue images to form a combined image; and

a projection lens for enlarging and projecting the combined image.

6. A projection display apparatus comprising:

a light source device including a linear emission lamp for emitting white light and a condenser lens receiving the white light;

color separating means, including two crossed dichroic mirrors, for separating the white light into red light, green light and blue light;

image display devices illuminated by separated red light, green light and blue light, and forming a red image, a green image, and a blue image, respectively;

color combining means for combining the red, green and blue images to form a combined image; and

a projection lens for enlarging and projecting the combined image;

said linear emission lamp arranged such that a longitudinal direction of said linear emission lamp is substantially perpendicular to a line formed by the intersection of the two crossed dichroic mirrors and substantially perpendicular to an optical axis of the projection display apparatus.

7. A projection display apparatus for forming an image onto a screen, comprising:

a light source for generating light;

a liquid-crystal light valve receiving light generated by said light source and transmitting image-bearing light;

a projection lens receiving the image-bearing light and projecting an enlarged image onto the screen;

a polarizing element interposed between said light source and said liquid-crystal light valve, said polarizing element including an incident surface and an emergent surface each of which includes a periodic fold structure and a triangular-wavelike shaped cross-section with each crest of the incident surface aligned with a trough of the emergent surface, and angles of incidence and emergence θ

i of the periodic fold structure set at a value equal to or larger than the Brewster angle θ

B, and vertex angles θ

P of opposite crest and trough angles substantially satisfy 0<

θ

P≦

σ

-2θ

B,

wherein the vertex angles θ

P formed by each of said folds orients the incident and emergent surfaces for substantially transmitting P-polarized light through said polarizing element with little loss and for substantially reflecting S-polarized light.

8. A method for optimizing an arrangement of a discharge lamp in a projection display apparatus having a rectangular image display device, comprising the steps of:

constructing a light source of the projection display apparatus with the discharge lamp, a spherical mirror and a condenser lens including the substeps of locating a center of emission of the discharge lamp at a position substantially corresponding to a center of curvature of the spherical mirror and locating the center of emission at a location substantially corresponding to a focal point of the condenser lens;

aligning a longitudinal direction of an electrode of the discharge lamp parallel to a direction in which a shorter side of the rectangular image display device extends;

emitting light from the center of emission of the discharge lamp;

reflecting the emitted light with the spherical mirror;

refracting the reflected light with the condenser lens; and

receiving the refracted light with the image display device,

wherein the arrangement of the projection display apparatus results in a uniform light distribution on the image display device.

9. A method for optimizing an arrangement of an exhaust vent, formed during manufacture of a discharge lamp, relative to a projection display apparatus having a rectangular image display device, comprising the steps of:

constructing a light source of the projection display apparatus with the discharge lamp, a spherical mirror and a condenser lens including the substeps of locating a center of emission of the discharge lamp at a position substantially corresponding to a center of curvature of the spherical mirror and locating the center of emission at a location substantially corresponding to a focal point of the condenser lens;

emitting light from the center of emission of the discharge lamp along an optical axis;

arranging the exhaust vent of the discharge lamp such that the exhaust vent faces a direction perpendicular to the direction in which the optical axis of the light extends;

reflecting the emitted light with the spherical mirror;

refracting the reflected light with the condenser lens;

receiving the refracted light with the image display device,

wherein the arrangement of the projection display apparatus results in a uniform light distribution on the image display device.