US 2026/0086332 A1Published application

Imaging optical system

AssigneeSigma Corporation

InventorYukihiro YAMAMOTO

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Abstract

Provided is an imaging optical system that is compatible with a large image sensor, and achieves both a large aperture ratio and good aberration correction in consideration of weight reduction of a focus lens that is mainly driven in focusing. An imaging optical system consists of, in order from an object side: a front group GrF having a positive refractive power; a first focus group GrFC1 having a negative refractive power; a second focus group GrFC2 having a negative refractive power; and a rear group GrR having a positive refractive power. During focusing from infinity to a short distance, the front group GrF and the rear group GrR are fixed with respect to an image surface, the first focus group GrFC1 moves to the image side. The second focus group GrFC2 moves to the object side, and specific conditional expressions are satisfied.

Claims22

Dependent claims

An imaging optical system comprising, in order from an object side:

a front group GrF having a positive refractive power;
a first focus group GrFC1 having a negative refractive power;
a second focus group GrFC2 having a negative refractive power;
and
a rear group GrR having a positive refractive power, wherein
during focusing from infinity to a short distance, the front group GrF and the rear group GrR are fixed with respect to an image surface, the first focus group GrFC1 moves to the image side, and the second focus group GrFC2 moves to the object side, and
following conditional expressions are satisfied:
0.2
<
LGrF
/
fF
<
1.4
(
1
)
0.42
<
f
/
fFC
⁢
2
⁢
R
<
4.
(
2
)
0.15
<
LGrFGrR
/
LALL
<
0.5
(
3
)
LGrF:
a length of the front group GrF on an optical axis in an infinity-focusing state
fF:
a focal length of the front group GrF in the infinity focusing state
f:
a focal length of the entire lens system at focusing on infinity
fFC2R:
a total focal length of the second focus group GrFC2 and the rear group GrR during focusing on infinity
LGrFGrR:
a length on the optical axis from a surface of the front group GrF closest to the image side to a surface of the rear group GrR closest to the object side in the infinity focusing state
LALL:
a length on the optical axis from a surface of the front group GrF closest to the object side to an image surface in the infinity focusing state.

50 more elements

An imaging optical system comprising, in order from an object side:

a front group GrF having a positive refractive power;
a first focus group GrFC1 having a negative refractive power;
a second focus group GrFC2 having a negative refractive power;
and
a rear group GrR having a positive refractive power, wherein
during focusing from infinity to a short distance, the front group GrF and the rear group GrR are fixed with respect to an image surface, the first focus group GrFC1 moves to the image side, and the second focus group GrFC2 moves to the object side, and
following conditional expression is satisfied:
0
.
0
⁢
00
<
❘
"\[LeftBracketingBar]"
K
⁢
2
❘
"\[RightBracketingBar]"
<
0.
3
⁢
7
⁢
0
(
5
)
|K2|:
focus sensitivity of the second focus group GrFC2 in the infinity-focusing state
❘
"\[LeftBracketingBar]"
K
⁢
2
❘
"\[RightBracketingBar]"
=
❘
"\[LeftBracketingBar]"
(
1
-
βFC2
^
2
)
⋆
(
βR
^
2
)
❘
"\[RightBracketingBar]"
ßFC2:
lateral magnification of the second focus group GrFC2 in the infinity-focusing state
ßR:
lateral magnification of the rear group GR in the infinity-focusing state.

58 more elements

An imaging optical system comprising, in order from an object side:

a front group GrF having a positive refractive power;
a first focus group GrFC1 having a negative refractive power;
a second focus group GrFC2;
and
a rear group GrR having a positive refractive power, wherein
during focusing from infinity to a short distance, the front group GrF and the rear group GrR are fixed with respect to an image surface, the first focus group GrFC1 moves to the image side, and the second focus group GrFC2 moves to the object side, and
following conditional expressions are satisfied:
0.
<
❘
"\[LeftBracketingBar]"
K
⁢
2
❘
"\[RightBracketingBar]"
<
0
.
3
⁢
7
⁢
0
(
5
)
0.107
<
Δ
⁢
Gr
⁢
1
⁢
GrFC
⁢
1
/
Y
⁢
max
<
1.
(
6
)
|K2|:
focus sensitivity of the second focus group GrFC2 in the infinity-focusing state
❘
"\[LeftBracketingBar]"
K
⁢
2
❘
"\[RightBracketingBar]"
=
❘
"\[LeftBracketingBar]"
(
1
-
βFC2
^
2
)
⋆
(
βR
^
2
)
❘
"\[RightBracketingBar]"
ßFC2:
lateral magnification of the second focus group GrFC2 in the infinity-focusing state
ßR:
lateral magnification of the rear group GR in the infinity-focusing state
ΔGr1GrFC1:
a length parallel to optical axis between a position of an axial ray height of a surface of the front group GrF closest to the image side and a position of an axial ray height of a surface of the first focus group GrFC1 closest to the object side in the infinity-focusing state
Ymax:
maximum image height.

79 more elements

Dependencies are inferred from the claim text.

Facts

Application: 19/325,938Filed 11 Sep 2025
Priority: JP 2024-16321720 Sep 2024
Published: 26 Mar 2026
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

G02B 13/0045
Having at least one aspherical surface: having five or more lenses
G02B 5/005
Optical elements other than lenses: diaphragms
G02B 13/006
Employing a special optical element: at least one element being a compound optical element, e.g. cemented elements
G02B 13/02
Optical objectives specially designed for the purposes specified below: telephoto objectives, i.e. systems of the type + - in which the distance…

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