# US 2018/0321476 A1 · Projection optical system and projection type display device

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- Number: US 2018/0321476 A1
- Document ID: US20180321476A1
- Status: Published application
- Kind: A1
- Application number: 16/031,244
- Filed: 2018-07-10
- Published: 2018-11-08
- Earliest claimed: 2015-02-25
- Assignees: FUJIFILM Corporation
- Applicants: FUJIFILM Corporation
- Inventors: Masaru AMANO
- Web page: https://patentgrep.com/patent/US20180321476A1

## CPC

- G02B 17/008: {Systems specially adapted to form image relays or chained systems}
- G02B 13/06: Panoramic objectives; So-called "sky lenses" {including panoramic objectives having reflecting surfaces}
- G02B 13/22: Telecentric objectives or lens systems
- G02B 13/16: for use in conjunction with image converters or intensifiers {, or for use with projectors, e.g. objectives for projection TV}
- G03B 21/28: Reflectors in projection beam {(in illumination beam G03B21/2066)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)

## Abstract

A projection optical system is constituted by, in order from the reduction side, a first optical system for forming an image displayed by image display elements as an intermediate image, a first optical path bending means that bends an optical path with a reflective surface, and a second optical system for forming the intermediate image on a magnification side conjugate plane. The second optical system is constituted by, in order from the reduction side, a first lens group having a positive refractive power, a second optical path bending means that bends an optical path with a reflective surface, and a second lens group having a positive refractive power. Conditional Formulae (1) and (2) below are satisfied. 10.0<TL1/|f|<50.0 (1) 4.0<TL21/|f|<30.0 (2).

## Claims

### Claim 1

A projection optical system that forms an intermediate image at a position conjugate to an image displayed by an image display element provided on a reduction side conjugate plane, and projects the intermediate image onto a magnification side conjugate plane as a magnified image, the projection optical system comprising:
a plurality of lenses; and
two optical path bending means for bending an optical path with a reflective surface by 90 degrees; wherein:
a lens is arranged at a position most toward a reduction side and a position most toward a magnification side of the entire system,
the plurality of lenses and the two optical path bending means are arranged at a position further away from the magnification side conjugate plane than the image display element, and
the image displayed by the image display element is projected as the magnified image which is inverted 180 degrees.

### Claim 2 (depends on 1)

A projection optical system as defined in claim 1, wherein a lens is arranged between the two optical path bending means.

### Claim 3 (depends on 1)

A projection optical system as defined in claim 1, consisting of, in order from the reduction side to the magnification side:
a first optical system constituted by a plurality of lenses that forms the image displayed by the image display element as the intermediate image;
a first optical path bending means for bending an optical path with a reflective surface 90 degrees; and
a second optical system constituted by a plurality of lenses that forms the intermediate image on the magnification side conjugate plane;
the second optical system consisting of, in order from the reduction side to the magnification side, a first lens group having a positive refractive power, a second optical path bending means for bending an optical path with a reflective surface 90 degrees, and a second lens group having a positive refractive power.

### Claim 4 (depends on 1)

A projection optical system as defined in claim 1, wherein the reduction side is telecentric.

### Claim 5 (depends on 1)

A projection optical system as defined in claim 1, wherein, among the plurality of lenses, a lens surface most toward the magnification side is arranged at a position further away from the magnification side conjugate plane than a lens surface most toward the reduction side.

### Claim 6 (depends on 1)

A projection optical system as defined in claim 1, wherein, among the plurality of lenses, a lens surface most toward the magnification side is an aspherical surface.

### Claim 7 (depends on 1)

A projection optical system as defined in claim 1, in which Conditional Formula (1) below is satisfied:
135≤2ω (1)
wherein 2ω is a full angle of view of the projection optical system.

### Claim 8 (depends on 3)

A projection optical system as defined in claim 3, in which Conditional Formula (2) below is satisfied:
1.50<f2/|f|<2.80 (2)
wherein f2 is a focal length of the second optical system, and f is a focal length of the entire projection optical system.

### Claim 9 (depends on 8)

A projection optical system as defined in claim 8, in which Conditional Formula (2-1) below is satisfied:
1.52<f2/|f|<2.20 (2-1).

### Claim 10 (depends on 3)

A projection optical system as defined in claim 3, in which Conditional Formula (3) below is satisfied:
8.20<Imφ·f2/f2<20.00 (3)
wherein Imφ is an effective image diameter at the reduction side, f2 is a focal length of the second optical system, and f is a focal length of the entire projection optical system.

### Claim 11 (depends on 10)

A projection optical system as defined in claim 10, in which Conditional Formula (3-1) below is satisfied:
8.30<Imφ·f2/f2<16.00 (3-1).

### Claim 12 (depends on 3)

A projection optical system as defined in claim 3, in which Conditional Formula (4) below is satisfied:
0.020<enP/TL2<0.160 (4)
wherein enP is a distance along an optical axis from a surface most toward the magnification side in the second optical system to a position of an entrance pupil in the case that the magnification side is a light entry side, and TL2 is a distance along the optical axis from a surface most toward the reduction side in the second optical system to the surface most toward the magnification side in the second optical system.

### Claim 13 (depends on 12)

A projection optical system as defined in claim 12, in which Conditional Formula (4-1) below is satisfied:
0.050<enP/TL2<0.145 (4-1).

### Claim 14 (depends on 3)

A projection optical system as defined in claim 3, in which Conditional Formula (5) below is satisfied:
0.125<Imφ/TL2<0.240 (5)
wherein Imφ is an effective image diameter at the reduction side, and TL2 is a distance along an optical axis from a surface most toward the reduction side in the second optical system to a surface most toward the magnification side in the second optical system.

### Claim 15 (depends on 14)

A projection optical system as defined in claim 14, in which Conditional Formula (5-1) below is satisfied:
0.130<Imφ/TL2<0.200 (5-1).

### Claim 16 (depends on 1)

A projection optical system as defined in claim 1, in which Conditional Formula (6) below is satisfied:
4.0<Bf/|f| (6)
wherein Bf is a back focus of the entire projection optical system and f is a focal length of the entire projection optical system.

### Claim 17 (depends on 1)

A projection type display device, comprising:
a light source;
light valves into which light from the light source enters; and
a projection optical system as defined in claim 1 as a projection optical system that projects, on a screen, an optical image formed by light which is optically modulated by the light valves.