US 12,169,268 B2
Magnification-variable optical system, optical apparatus, and method for manufacturing magnification-variable optical system
Fumiaki Ohtake, Tokyo (JP); and Azuna Nonaka, Yokohama (JP)
Assigned to Nikon Corporation, Tokyo (JP)
Appl. No. 17/432,368
Filed by Nikon Corporation, Tokyo (JP)
PCT Filed Dec. 20, 2019, PCT No. PCT/JP2019/050007
§ 371(c)(1), (2) Date Aug. 19, 2021,
PCT Pub. No. WO2020/170591, PCT Pub. Date Aug. 27, 2020.
Claims priority of application No. 2019-030151 (JP), filed on Feb. 22, 2019.
Prior Publication US 2022/0137378 A1, May 5, 2022
Int. Cl. G02B 15/14 (2006.01); G02B 3/04 (2006.01)
CPC G02B 15/1465 (2019.08) [G02B 3/04 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A magnification-variable optical system comprising:
a first lens group having negative refractive power; and
a rear group including at least one lens group disposed on an image side of the first lens group, wherein
a distance between lens groups adjacent to each other changes at magnification change,
the first lens group consists of, sequentially from the object side, a negative single lens, a negative single lens, a negative single lens, and a positive single lens, and
the following conditional expressions are satisfied:
−4.00<(L1r2+L1r1)/(L1r2−L1r1)<−0.50
100.00°<2ωw
1.42<(−f1)/fw<2.00
1.314≤fL1/f1<2.00
0.058≤(L3r2+L3r1)/(L3r2−L3r1)<0.80
where
L1r1: radius of curvature of a lens surface of a lens closest to an object side in the first lens group, the lens surface being on the object side,
L1r2: radius of curvature of a lens surface of the lens closest to the object side in the first lens group, the lens surface being on an image side,
2ωw: full angle of view of the magnification-variable optical system in a wide-angle state,
fw: focal length of the magnification-variable optical system in the wide-angle state,
f1: focal length of the first lens group,
fL1: focal length of the lens closest to the object side in the first lens group,
L3r1: radius of curvature of a lens surface of a lens third closest to the object side in the first lens group, the lens surface being on the object side, and
L3r2: radius of curvature of a lens surface of the lens third closest to the object side in the first lens group, the lens surface being on the image side.