US 9,810,976 B2
Projection optical system
Nobutaka Minefuji, Azumino (JP)
Assigned to SEIKO EPSON CORPORATION, Tokyo (JP)
Filed by SEIKO EPSON CORPORATION, Tokyo (JP)
Filed on Jun. 22, 2016, as Appl. No. 15/189,564.
Application 15/189,564 is a continuation of application No. 15/003,200, filed on Jan. 21, 2016, abandoned.
Claims priority of application No. 2015-013031 (JP), filed on Jan. 27, 2015.
Prior Publication US 2016/0306268 A1, Oct. 20, 2016
Int. Cl. G02B 3/00 (2006.01); G02B 9/00 (2006.01); G02B 17/00 (2006.01); G03B 21/14 (2006.01); G02B 27/00 (2006.01); G03B 21/28 (2006.01); G02B 15/16 (2006.01); G02B 15/20 (2006.01); G02B 7/04 (2006.01); G03B 21/00 (2006.01); H04N 9/31 (2006.01); G02B 3/02 (2006.01); G02B 13/00 (2006.01); G02B 17/08 (2006.01); G02B 13/16 (2006.01); G02B 15/14 (2006.01); G02B 13/22 (2006.01); G03B 5/00 (2006.01); G02B 5/00 (2006.01); G02B 13/18 (2006.01); G03B 17/54 (2006.01)
CPC G03B 21/147 (2013.01) [G02B 7/04 (2013.01); G02B 15/161 (2013.01); G02B 15/20 (2013.01); G02B 17/0852 (2013.01); G02B 17/0896 (2013.01); G02B 27/0025 (2013.01); G03B 21/006 (2013.01); G03B 21/28 (2013.01); H04N 9/315 (2013.01); G02B 3/02 (2013.01); G02B 5/005 (2013.01); G02B 13/009 (2013.01); G02B 13/0045 (2013.01); G02B 13/0065 (2013.01); G02B 13/16 (2013.01); G02B 13/18 (2013.01); G02B 13/22 (2013.01); G02B 15/14 (2013.01); G02B 17/08 (2013.01); G02B 17/0816 (2013.01); G03B 5/00 (2013.01); G03B 17/54 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A projection optical system comprising:
in order from a reduction side,
a first optical group which is formed of a plurality of lenses and has positive power; and
a second optical group which has one reflective surface having a concave aspheric shape,
wherein the first optical group is formed to include a 1-1st lens group which is fixed when focusing is performed during the magnification change and has positive power, and a 1-2nd lens group which moves when focusing is performed during the magnification change, is formed of a plurality of lenses, and has positive power as a whole, and
wherein the 1-2nd lens group is a lens group which individually moves when focusing is performed during the magnification change, and includes three lens groups of a positive F1 lens group formed of at least two lenses, F2 lens group formed of only two lenses, and F3 lens group formed of one negative lens.