US 12,007,678 B2
Projection system and projector with first optical system and second optical system
Yasuyuki Kiyama, Suwa (JP); Hitoshi Hirano, Suwa (JP); Nobutaka Minefuji, Omachi (JP); and Koji Shiokawa, Suzaka (JP)
Assigned to SEIKO EPSON CORPORATION, Tokyo (JP)
Filed by SEIKO EPSON CORPORATION, Tokyo (JP)
Filed on Dec. 23, 2021, as Appl. No. 17/560,384.
Claims priority of application No. 2020-214690 (JP), filed on Dec. 24, 2020.
Prior Publication US 2022/0206252 A1, Jun. 30, 2022
Int. Cl. G03B 21/28 (2006.01); G02B 9/10 (2006.01); G02B 13/16 (2006.01)
CPC G03B 21/28 (2013.01) [G02B 9/10 (2013.01); G02B 13/16 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A projection system comprising:
a first optical system having positive power; and
a second optical system disposed on a reduction side of the first optical system,
wherein an intermediate image conjugate with an enlargement-side conjugate plane and a reduction-side conjugate plane of the projection system is formed between the first optical system and the second optical system,
the second optical system includes
a first lens group disposed on the enlargement side of a first intersection position where a chief ray of an off-axis beam having a maximum angle of view intersects with an optical axis of the projection system in the second optical system,
a second lens group disposed on the reduction side of the first intersection position and having negative power, and
a third lens group disposed on the reduction side of the second lens group and having positive power,
the second lens group includes a first lens having positive power, a second lens disposed on the reduction side of the first lens and having positive power, and a third lens disposed on the reduction side of the second lens and having negative power,
the third lens group includes two lenses each having positive power, and
a conditional expression (1) below is satisfied,
−0.5<fLU2G3/fLU2G2<0  (1)
where fLU2G2 is a focal length of the second lens group, and fLU2G3 is a focal length of the third lens group.