Projection optical system and image projection device for projecting an image light flux onto a projection surface

• US 10,444,612 B2
• Filed: 02/27/2018
• Issued: 10/15/2019
• Est. Priority Date: 07/04/2016
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: Uchida, Tsuneo, Yamada, Katsu
• Primary Examiner(s): Le, Bao-Luan Q
• Application Number:
  US15/906,365
• Publication Number:
  US 20180188507A1
• Time in Patent Office: 595 Days
• CPC Class Codes: G02B 13/16 for use in conjunction with image converters or intensifiers , or for use with projectors, e.g. objectives for projection TV
• 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 15/144115 arranged ++++
• CPC Class Codes: G02B 17/08 Catadioptric systems used in non-imaging applications G02B19/00
• CPC Class Codes: G03B 21/00 Projectors or projection-type viewers; Accessories therefor devices for changing pictures G03B23/00
• CPC Class Codes: G03B 21/14 Details
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor

Abstract

A projection optical system is an optical system for projecting an image light flux formed in an image display element onto a projection surface, and includes a transmission optical system and a reflection optical system. The transmission optical system is located on an emission surface side of the image display element and includes a stop and a plurality of lenses. The reflection optical system includes a positive-power first mirror and a second mirror. Conditional Expression (1) is satisfied
0<TL/ft<10  (1)
where

• • ft is a focal length of the transmission optical system, and
  • TL is a distance parallel to an optical axis of the transmission optical system from a position where the first mirror reflects a principal ray of the image light flux, to the image display element.

Claims

1. A projection optical system for projecting an image light flux formed in an image display element onto a projection surface, the projection optical system comprising:

a transmission optical system that is located on an emission surface side of the image display element and includes a stop and a plurality of lenses; and

a reflection optical system that includes a positive-power first mirror and a second mirror, the first mirror reflecting light output from the transmission optical system, the second mirror reflecting reflected light of the first mirror toward the projection surface,

wherein Conditional Expression (1) is satisfied

0<

TL/ft<

5.0 

 

(1)

where

ft is a focal length of the transmission optical system, and

TL is a distance parallel to an optical axis of the transmission optical system from a position where the first mirror reflects a principal ray of the image light flux, which passes through a center in a long-side direction of the image display element and is projected onto the projection surface closest to a projection optical system side, to the image display element wherein Conditional Expression (4) is satisfied

0<

T2/T1<

5 

 

(4)

where

T1 is a total of a distance from a position of a principal ray of the image light flux reflected by the first mirror farthest from the optical axis in a short-side direction of the image display element to the optical axis and a distance from a position of a principal ray of the image light flux reflected by the second mirror farthest from the optical axis in the short-side direction of the image display element to the optical axis, and

T2 is an optical path length of the principal ray from a lens located closest to the projection surface among the plurality of the lenses, to the first mirror.

2. The projection optical system according to claim 1, wherein Conditional Expression (5) is satisfied

0<

T2/ft<

5 

 

(5).

3. The projection optical system according to claim 1, wherein Conditional Expression (6) is satisfied

0<

T1/ft<

3 

 

(6).

4. The projection optical system according to claim 1, wherein Conditional Expression (7) is satisfied

0.005<

Tr×

(T1/ft)<

1 

 

(7)

where

Tr is a throw ratio of the projection optical system.

5. The projection optical system according to claim 1, wherein Conditional Expression (8) is satisfied

0.1<

fmmax/ft<

10 

 

(8)

where

fmmax is a maximum focal length on a surface of the first mirror.

6. The projection optical system according to claim 1, wherein the projection surface has a curvature.

7. An image projection device comprising:

the projection optical system according to claim 1; and

the image display element.

8. A projection optical system for projecting an image light flux formed in an image display element onto a projection surface, the projection optical system comprising:

a transmission optical system that is located on an emission surface side of the image display element and includes a stop and a plurality of lenses; and

a reflection optical system that includes a positive-power first mirror and a second mirror, the first mirror reflecting light output from the transmission optical system, the second mirror reflecting reflected light of the first mirror toward the projection surface,

wherein Conditional Expression (1) is satisfied

0<

TL/ft<

5.0 

 

(1)

where

ft is a focal length of the transmission optical system, and

TL is a distance parallel to an optical axis of the transmission optical system from a position where the first mirror reflects a principal ray of the image light flux, which passes through a center in a long-side direction of the image display element and is projected onto the projection surface closest to a projection optical system side, to the image display element, wherein Conditional Expression (9) is satisfied

0.001<

fmmin/ft≤

0.1 

 

(9)

where

fmmin is a minimum focal length on a surface of the first mirror.

9. The projection optical system according to claim 8, wherein Conditional Expression (8) is satisfied

0.1<

fmmax/ft<

10 

 

(8)

where

fmmax is a maximum focal length on a surface of the first mirror.

10. The projection optical system according to claim 8, wherein the projection surface has a curvature.

11. An image projection device comprising:

the projection optical system according to claim 8; and

the image display element.