US 12,443,008 B2
Projection system and projector
Hitoshi Hirano, Suwa (JP); Hirotaka Yanagisawa, Azumino (JP); and Akihisa Kageyama, Matsumoto (JP)
Assigned to SEIKO EPSON CORPORATION, Tokyo (JP)
Filed by SEIKO EPSON CORPORATION, Tokyo (JP)
Filed on Mar. 29, 2023, as Appl. No. 18/191,958.
Claims priority of application No. 2022-054797 (JP), filed on Mar. 30, 2022.
Prior Publication US 2023/0314764 A1, Oct. 5, 2023
Int. Cl. G02B 13/22 (2006.01); G02B 9/06 (2006.01); G02B 13/00 (2006.01); G02B 13/16 (2006.01); G03B 21/14 (2006.01)
CPC G02B 9/06 (2013.01) [G02B 13/16 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A projection system comprising a first lens group having refractive power, an aperture diaphragm, and a second lens group having refractive power sequentially from an enlargement side toward a reduction side, wherein
a reduction side of the second lens group is telecentric,
the first lens group includes a first sub-lens group having negative power and a second sub-lens group having positive power sequentially from the enlargement side toward the reduction side,
an air gap is provided between a lens located at the most reduction side of the first sub-lens group and a lens located at the most enlargement side of the second sub-lens group, the air gap being wider than air gaps between lenses that are other than the lens located at the most reduction side of the first sub-lens group and the lens located at the most enlargement side of the second sub-lens group and that are adjacent to each other,
a lens located at the most reduction side in the first lens group is a positive lens,
the second lens group includes a cemented lens,
the cemented lens includes a first lens having negative power, a second lens having positive power, and a third lens having negative power sequentially from the enlargement side toward the reduction side,
ω>40
where a maximum half angle of view of an entire lens system is @,
vdp<40, and
1.5<Flp/F<15.0
where a focal length of the entire lens system is F, a focal length of the positive lens located at the most reduction side in the first lens group is Flp, and an Abbe's number of the positive lens located at the most reduction side in the first lens group in d ray is vdp.