US 12,235,422 B2
Zoom optical system, optical apparatus and method for manufacturing the zoom optical system
Kosuke Machida, Tokyo (JP)
Assigned to Nikon Corporation, Tokyo (JP)
Filed by Nikon Corporation, Tokyo (JP)
Filed on Jan. 16, 2024, as Appl. No. 18/413,590.
Application 18/413,590 is a division of application No. 17/311,329, granted, now 11,960,065, previously published as PCT/JP2018/047775, filed on Dec. 26, 2018.
Prior Publication US 2024/0151953 A1, May 9, 2024
Int. Cl. G02B 15/14 (2006.01); G02B 15/20 (2006.01); G02B 27/00 (2006.01)
CPC G02B 15/144113 (2019.08) [G02B 15/20 (2013.01); G02B 27/0025 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A zoom optical system, comprising, in order from an object: a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; a fourth lens group having a positive refractive power; and a succeeding lens group, wherein
upon zooming, distances between adjacent lens groups change, and
the succeeding lens group includes a focusing lens group that moves upon focusing and disposed on the most object side, and
the following conditional expressions are satisfied:
0.80<f1/f4<5.10
0.20<f3/f4<2.50
f1/|fRw|<4.00
0.10<BFw/fw<1.00
where
f1: a focal length of the first lens group,
f3: a focal length of the third lens group,
f4: a focal length of the fourth lens group,
fRw: a focal length of the succeeding lens group in a wide-angle end state,
BFw: a back focus of the zoom optical system in a wide-angle end state, and
fw: a focal length of the zoom optical system in a wide-angle end state.