US 12,332,413 B2
Variable magnification optical system, optical equipment, and method for producing variable magnification optical system
Takahiro Ishikawa, Kawasaki (JP); and Norikazu Yokoi, Yokohama (JP)
Assigned to Nikon Corporation, Tokyo (JP)
Appl. No. 17/279,566
Filed by Nikon Corporation, Tokyo (JP)
PCT Filed Nov. 20, 2018, PCT No. PCT/JP2018/042793
§ 371(c)(1), (2) Date Mar. 24, 2021,
PCT Pub. No. WO2020/105110, PCT Pub. Date May 28, 2020.
Prior Publication US 2021/0396976 A1, Dec. 23, 2021
Int. Cl. G02B 15/14 (2006.01); G02B 13/00 (2006.01); G02B 13/02 (2006.01); G02B 27/64 (2006.01)
CPC G02B 15/145105 (2019.08) [G02B 13/02 (2013.01); G02B 27/646 (2013.01); G02B 13/0045 (2013.01)] 25 Claims
OG exemplary drawing
 
1. A variable magnification optical system comprising a plurality of lens groups including a first positive lens group disposed at a most object side and having positive refractive power, a first negative lens group disposed at an image side of the first positive lens group and having negative refractive power, and a second negative lens group disposed at a more image side than the first negative lens group and having negative refractive power;
the variable magnification optical system further comprising a second positive lens group disposed between the first negative lens group and the second negative lens group and having positive refractive power;
an aperture stop being disposed between the first negative lens group and the second negative lens group;
upon varying a magnification, distances between adjacent lens groups being varied;
the first negative lens group including, in order from the object side, a first negative lens, a second negative lens and a positive lens;
the second negative lens group being moved along the optical axis upon carrying out focusing; and
the following conditional expressions being satisfied:
0.200<(−f2n)/√(fw*ft)<1.000
0.500<f2p/(−f1n)<1.500
−1.000<β1nt/β2nt<−0.530
where f2n denotes a focal length of the second negative lens group, fw denotes a focal length of the variable magnification optical system as a whole in the wide angle end state, ft denotes a focal length of the variable magnification optical system as a whole in the telephoto end state, f2p denotes a focal length of the second positive lens group, f1n denotes a focal length of the first negative lens group, β1nt denotes a transverse magnification of the first negative lens group in the telephoto end state, and β2nt denotes a transverse magnification of the second negative lens group in the telephoto end state.