US 12,235,465 B2
Projection system and projector
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 Jul. 29, 2022, as Appl. No. 17/876,806.
Claims priority of application No. 2021-124881 (JP), filed on Jul. 30, 2021.
Prior Publication US 2023/0049785 A1, Feb. 16, 2023
Int. Cl. G02B 27/09 (2006.01); G02B 3/04 (2006.01); H04N 9/31 (2006.01)
CPC G02B 27/0955 (2013.01) [G02B 3/04 (2013.01); H04N 9/3152 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A projection system that projects an image in a reduction-side conjugate plane onto an enlargement-side conjugate plane, the projection system comprising:
a first optical system; and
a second optical system disposed on an enlargement side of the first optical system,
wherein the first optical system includes a first lens group having positive power, a second lens group disposed on the enlargement side of the first lens group and having negative power, and an optical path deflector disposed between the first lens group and the second lens group,
the second optical system includes a reflection member having a concave reflection surface,
the second lens group includes three aspherical lenses,
Conditional Expression (1) below is satisfied,
0.25<|F|×FNO/Ymax<0.5  (1)
where F represents a focal length of entirety of the projection system, FNO represents an F number of the projection system, and Ymax represents a maximum image height in the reduction-side conjugate plane, and
wherein Conditional Expression (2) below is satisfied,
0.15<Dg1/TTL<0.30  (2)
where TTL is an optical path length from the reduction-side conjugate plane to the reflection surface, and Dg1 represents a length of the first lens group.