Optical system having intermediate image formed therein

Patent metadata

Field	Value
Publication number	US-12411323-B2
Application number	US-202117928425-A
Country	US
Kind code	B2
Filing date	Jun 16, 2021
Priority date	Jun 16, 2020
Publication date	Sep 9, 2025
Grant date	Sep 9, 2025

Abstract

An optical system includes a first optical subsystem disposed on an enlargement side and a second optical subsystem disposed on a reduction side with an intermediate image in between. The first optical subsystem includes: a first lens group that is disposed on the enlargement side of a first stop with a first distance, in which other lenses could be disposed but no other lenses are disposed, and is provided on the enlargement side with a first component with negative refractive power; and a second lens group that has positive refractive power, is disposed on the reduction side of the first stop with a second distance, in which other lenses could be disposed but no lenses are disposed, and forms the intermediate image so as to be adjacent on a reduction side of the second lens group and so as to be tilted toward the enlargement side.

First claim

The invention claimed is:

1. An optical system composed of a first optical subsystem disposed on an enlargement side and a second optical subsystem disposed on a reduction side with an intermediate image in between,
wherein the first optical subsystem includes:
a first lens group that is disposed on the enlargement side of a first stop with a first distance that includes a spacing in which no other lenses are disposed, and the first lens group includes, on the enlargement side of the first lens group, a first component with negative refractive power, and
a second lens group that has positive refractive power, is disposed on the reduction side of the first stop with a second distance that includes a spacing in which no other lenses are disposed, and forms the intermediate image so as to be adjacent on the reduction side of the second lens group and so as to be tilted toward the enlargement side;
wherein the first distance SP1, the second distance SP2 and an effective diameter SD1 of the first stop satisfy following conditions:
0.5 <SP 1 /SD 1 <1.7,
0.5 <SP 2 /SD 1 <1.7, and

the first optical subsystem includes a focus group including one or more lenses that move during focusing and the focus group includes a first lens with negative refractive power disposed closest to the enlargement side of the first lens group, the first lens being included in the first component of the first lens group.

2. The optical system according to claim 1 ,
wherein the second lens group includes a plurality of lenses and a maximum effective diameter Dg2max and a minimum effective diameter Dg2min of the lenses satisfy a following condition:
1 <Dg 2max/ Dg 2 min<1.7.

3. The optical system according to claim 1 ,
wherein the second lens group includes a plurality of lenses with positive refractive power respectively, and
a length Lg2 from a surface facing the first stop in the second lens group and a surface facing the intermediate image and a thickness Lg2p occupied by the plurality of lenses with positive refractive power satisfy a following condition:
0.5 <Lg 2 p/Lg 2<1.0.

4. The optical system according to claim 1 ,
wherein a focal length f1 of the first optical subsystem and a focal length fw at a wide angle end of the optical system satisfies a following condition:
1.0 <|f 1 /fw|< 2.0.

5. The optical system according to claim 1 ,
wherein the second lens group includes, at a position closest to the reduction side, a group end lens with positive refractive power that is adjacent on the enlargement side to the intermediate image, and a focal length fg2e of the group end lens and a focal length fw of the optical system at a wide angle end satisfy a following condition:
2.5 <|fg 2 e/fw|< 10.0.

6. The optical system according to claim 1 ,
wherein the second lens group includes, at a position closest to the reduction side, a group end lens with positive refractive power that is adjacent on the enlargement side to the intermediate image, and a radius of curvature Rg2er of a surface on the enlargement side of the group end lens and a focal length fw of the optical system at a wide angle end satisfy a following condition:
2.0 <|Rg 2 er/fw|< 35.0.

7. The optical system according to claim 1 ,
wherein the second lens group includes a second component composed of a combination of positive-negative-positive refractive powers at a position closest to the intermediate image.

8. The optical system according to claim 1 ,
wherein the second lens group includes, at a position closest to the intermediate image, a lens with positive refractive power that is convex on the reduction side.

9. The optical system according to claim 1 ,
wherein the focus group includes, in addition to the first lens, at least one lens included in the first optical subsystem.

10. The optical system according to claim 1 ,
wherein the focus group includes, in addition to the first lens, at least one lens with positive refractive power included in the second lens group.

11. The optical system according to claim 1 ,
wherein the focus group includes a first focus lens group including the first lens and a second focus lens group that moves differently to the first focus lens group.

12. An optical system composed of a first optical subsystem disposed on an enlargement side and a second optical subsystem disposed on a reduction side with an intermediate image in between,
wherein the first optical subsystem includes:
a first lens group that is disposed on the enlargement side of a first stop with a first distance that includes a spacing in which no other lenses are disposed, and the first lens group includes, on the enlargement side of the first lens group, a first component with negative refractive power, and
a second lens group that has positive refractive power, is disposed on the reduction side of the first stop with a second distance that includes a spacing in which no other lenses are disposed, and forms the intermediate image so as to be adjacent on the reduction side of the second lens group and so as to be tilted toward the enlargement side;

wherein the second optical subsystem includes:
a third lens group that is disposed on the enlargement side of a second stop at a third distance that includes a spacing in which no other lenses are disposed, and the third lens group includes, on an enlargement side of the third lens group, a third component with negative refractive power; and
a fourth lens group that has positive refractive power and is disposed on the reduction side of the second stop with a fourth distance that includes a spacing in which other lenses could be disposed but no other lenses are disposed;

wherein the third component of the third lens group is disposed adjacent to the intermediate image and includes, in order from the enlargement side, a lens that has positive refractive power and is closest to the intermediate image and two lenses with negative refractive power;
wherein the first distance SP1, the second distance SP2 and an effective diameter SD1 of the first stop satisfy following conditions:
0.5 <SP 1 /SD 1 <1.7,
0.5 <SP 2 /SD 1 <1.7, and

wherein the third distance SP3, the fourth distance SP4, and an effective diameter SD2 of the second stop satisfy following conditions:
0.4 <SP 3 /SD 2 <1.5,
0.4< SP 4 /SD 2 <1.5.

13. The optical system according to claim 12
wherein a focal length fc1 of the first component and a focal length fc3 of the third component satisfy a following condition:
0.1 <fc 1 /fc 3 <0.3.

14. The optical system according to claim 12 ,
wherein a focal length fc1 of the first component and a focal length fc3 of the third component satisfy a following condition:
0.8 <fc 1 /fc 3 <1.2.

15. The optical system according to claim 12 ,
wherein a total length Lop of the optical system and a total length Lop1 of the first optical subsystem satisfy a following condition:
0.2 <Lop 1 /Lop< 0.33.

16. The optical system according to claim 12 ,
wherein the third lens group includes a lens with positive refractive power that is convex on the enlargement side, is disposed closest to the enlargement side, and is adjacent on the reduction side of the intermediate image.

17. An optical system composed of a first optical subsystem disposed on an enlargement side and a second optical subsystem disposed on a reduction side with an intermediate image in between,
wherein the first optical subsystem includes:
a first lens group that is disposed on the enlargement side of a first stop with a first distance that includes a

Assignees

• Nittoh Inc

Inventors

• Matsuo Takahiko

Classifications

• G02B13/18

  with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)} · CPC title

• G02B13/04 Primary

  Reversed telephoto objectives · CPC title

• G02B15/144515

  arranged -+++ · CPC title

• G02B15/1425 Primary

  the first group being negative · CPC title