US 12,650,582 B2Granted

Projection system and projector

AssigneeSeiko Epson Corporation

InventorsNobutaka Minefuji, Hitoshi Hirano

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Abstract

A projection system includes first and second lens groups respectively having negative and positive power sequentially arranged from the enlargement side toward the reduction side. The first lens group includes a first-a lens group having negative power, a first-b lens group located at the reduction side of the first-a lens group and having negative power, and a first-c lens group located at the reduction side of the first-b lens group and having positive power. The first-b lens group and the first-c lens group each move in the direction of the optical axis during focusing. The projection system satisfies 0.2<|F/F1b|<0.6 (1), 0.0<F/F1c<0.14 (2), BF/F>5.0 (3), where F, F1b, and F1c represent the respective focal lengths of the overall projection system, first-b lens group, and first-c lens group, and BF represents the back focal length in air.

Claims11

Dependent claims

A projection system comprising

a first lens group having negative power and a second lens group having positive power sequentially arranged from an enlargement side of the projection system toward a reduction side of the projection system, the second lens group having an enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system,
wherein
the first lens group includes a first-a lens group having negative power and an enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system, a first-b lens group located at the reduction side of the first-a lens group and having negative power and an enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system, and a first-c lens group located at the reduction side of the first-b lens group and having positive power,
a first lens located in the first-a lens group at a position closest to the enlargement side of the first-a lens group has negative power in a vicinity of an optical axis and aspheric surfaces at opposite sides,
the first-b lens group and the first-c lens group are each configured to be movable in a direction of the optical axis during focusing,
the projection system satisfies each of Conditional Expressions (1) to (3) below,
0.2<|F/F1b|<0.6 (1)
0.0<F/F1c<0.14 (2)
BF/F>5.0 (3)
where F represents a focal length of the projection system, F1b represents a focal length of the first-b lens group, F1c represents a focal length of the first-c lens group, and BF represents a back focal length in air,
a stop is disposed in the second lens group at a position where a chief ray having a largest angle of view intersects with the optical axis, the stop having an enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system,
the second lens group includes a second-a lens group and a second-b lens group located at the enlargement side of the stop, the second-b lens group having enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system,
the second-a lens group is located at the enlargement side of the second-b lens group, and
the second-a lens group and the second-b lens group are each configured to be movable in the direction of the optical axis during zooming.

11 more elements

A projection system comprising

a first lens group having negative power and a second lens group having positive power sequentially arranged from an enlargement side of the projection system toward a reduction side of the projection system, the second lens group having an enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system,
wherein
the first lens group includes a first-a lens group having negative power and an enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system, a first-b lens group located at the reduction side of the first-a lens group and having negative power and an enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system, and a first-c lens group located at the reduction side of the first-b lens group and having positive power,
a first lens located in the first-a lens group at a position closest to the enlargement side of the first-a lens group has negative power in a vicinity of an optical axis and aspheric surfaces at opposite sides,
the first-b lens group and the first-c lens group are each configured to be movable in a direction of the optical axis during focusing, the projection system satisfies each of Conditional Expressions (1) to (3) below,
0.2<|F/F1b|<0.6 (1)
0.0<F/F1c<0.14 (2)
BF/F>5.0 (3)
where F represents a focal length of the projection system, F1b represents a focal length of the first-b lens group, F1c represents a focal length of the first-c lens group, and BF represents a back focal length in air,
the first-a lens group is formed only of a lens having negative power,
the first-b lens group is formed only of a lens having negative power,
a sum of a number of lenses of the first-a lens group and a number of lenses of the first-b lens group is smaller than or equal to three, and
the projection system satisfies Conditional Expression (4) below,
0.3<|F/F1ab|<1.0 (4)
where F represents the focal length of the entire projection system, and F1ab represents a combined focal length of the first-a lens group and the first-b lens group.

12 more elements

A projection system comprising

a first lens group having negative power and a second lens group having positive power sequentially arranged from an enlargement side of the projection system toward a reduction side of the projection system, the second lens group having an enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system,
wherein
the first lens group includes a first-a lens group having negative power and an enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system, a first-b lens group located at the reduction side of the first-a lens group and having negative power and an enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system, and a first-c lens group located at the reduction side of the first-b lens group and having positive power,
a first lens located in the first-a lens group at a position closest to the enlargement side of the first-a lens group has negative power in a vicinity of an optical axis and aspheric surfaces at opposite sides, the first lens having an enlargement side and a reduction side that respectively correspond to the enlargement side of the projection system and the reduction side of the projection system,
the first-b lens group and the first-c lens group are each configured to be movable in a direction of the optical axis during focusing,
the projection system satisfies each of Conditional Expressions (1) to (3) below,
0.2<|F/F1b|<0.6 (1)
0.0<F/F1c<0.14 (2)
BF/F>5.0 (3)
where F represents a focal length of the projection system, F1b represents a focal length of the first-b lens group, F1c represents a focal length of the first-c lens group, and BF represents a back focal length in air,
the first-a lens group is formed of the first lens and a second lens located at the reduction side of the first lens,
the first lens is made of resin,
the second lens is a meniscus lens having negative power and a convex enlargement-side surface,
the first-b lens group is formed of a third lens,
the third lens has negative power and a concave reduction-side surface, and
an enlargement-side surface of the third lens has power smaller than power of the concave reduction-side surface of the third lens.

13 more elements

Dependencies are inferred from the claim text.

Facts

Application: 18/072,121Filed 30 Nov 2022
Priority: JP 2021-1952681 Dec 2021
Published: US 2023/0168477 A11 Jun 2023
Granted: 9 Jun 2026
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

G02B 13/16
Optical objectives specially designed for the purposes specified below: for use in conjunction with image converters or intensifiers , or for use…
G02B 15/1465
Having more than five groups: the first group being negative
G02B 13/22
Optical objectives specially designed for the purposes specified below: telecentric objectives or lens systems
G02B
Optical elements, systems or apparatus