# US 10,768,397 B2 · Projection optical system and projection type display device

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- Number: US 10,768,397 B2
- Document ID: US10768397B2
- Status: Granted
- Kind: B2
- Application number: 16/129,668
- Filed: 2018-09-12
- Published: 2019-01-10
- Granted: 2020-09-08
- Earliest claimed: 2015-02-25
- Assignees: FUJIFILM Corporation
- Applicants: FUJIFILM Corporation
- Inventors: Masaru Amano
- Web page: https://patentgrep.com/patent/US10768397B2

## 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 first optical system constituted by a first plurality of lenses that forms the image displayed by the image display elements as an intermediate image;
a second optical system constituted by a second plurality of lenses that focuses the intermediate image on the magnification side conjugate plane; and
two reflective surfaces positioned to bend an optical path by 90 degrees; wherein:
at least a first lens of the first plurality of lenses is arranged at a position of a reduction side from the two reflective surfaces, and at least a second lens of the second plurality of lenses is arranged at a position of a magnification side from the two reflective surfaces;
in which Conditional Formulae (1) and (3) below being satisfied:
10.0<TL1/|f|<50.0 (1)
8.0<D12/|f|<30.0 (3)
wherein TL1 is the distance along the optical axis from the surface most toward the reduction side to the surface most toward the magnification side within the first optical system, D12 is the distance along the optical axis between the first optical system and the second optical system, and f is the focal length of the entire projection optical system.

### Claim 2 (depends on 1)

A projection optical system as defined in claim 1, in which Conditional Formula (1-1) below is satisfied:
15.0<TL1/|f|<40.0 (1-1).

### Claim 3 (depends on 1)

A projection optical system as defined in claim 1, in which Conditional Formula (1-1a) below is satisfied:
19.68≤TL1/|f|<50.0 (1-1a).

### Claim 4 (depends on 2)

A projection optical system as defined in claim 2, in which Conditional Formula (1-1b) below is satisfied:
19.68≤TL1/|f|<40.0 (1-1b).

### Claim 5 (depends on 1)

A projection optical system as defined in claim 1, in which Conditional Formula (3-1) below is satisfied:
10.0<D12/|f|<25.0 (3-1).

### Claim 6 (depends on 5)

A projection optical system as defined in claim 5, in which Conditional Formula (3-1a) below is satisfied:
10.0<D12/|f|≤21.45 (3-1a).

### Claim 7 (depends on 1)

A projection optical system as defined in claim 1, in which Conditional Formula (8) below is satisfied:
0.125<Imφ/TL2<0.240 (8)
wherein Imφ is the effective image diameter at the reduction side, and TL2 is the distance along the optical axis from the 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 8 (depends on 7)

A projection optical system as defined in claim 7, in which Conditional Formula (8-1) below is satisfied:
0.130<Imφ/TL2<0.200 (8-1).

### Claim 9 (depends on 1)

A projection optical system as defined in claim 1, in which Conditional Formula (10) below is satisfied:
4.0<Bf/|f| (10)
wherein Bf is the back focus (air converted distance) of the entire projection optical system.

### Claim 10 (depends on 1)

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

### Claim 11 (depends on 1)

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

### Claim 12 (depends on 1)

A projection optical system as defined in claim 1, in which Conditional Formula (11) below is satisfied:
135≤2ω (11)
wherein 2ω is a full angle of view of the projection optical system.

### Claim 13 (depends on 1)

A projection optical system as defined in claim 1, wherein:
the intermediate image is configured such that the peripheral portion has more field curvature toward the first optical system than the portion thereof at the center of the optical axis.

### Claim 14 (depends on 1)

A projection optical system as defined in claim 1, wherein:
the image displayed by the image display element is projected as the magnified image which is inverted 180 degrees.

### Claim 15 (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.