US 12,189,101 B2
Zoom optical system, optical apparatus and method for manufacturing the zoom optical system
Kosuke Machida, Tokyo (JP)
Assigned to Nikon Corporation, Tokyo (JP)
Appl. No. 17/595,851
Filed by Nikon Corporation, Tokyo (JP)
PCT Filed May 27, 2020, PCT No. PCT/JP2020/020821
§ 371(c)(1), (2) Date Nov. 28, 2021,
PCT Pub. No. WO2020/250672, PCT Pub. Date Dec. 17, 2020.
Claims priority of application No. 2019-110863 (JP), filed on Jun. 14, 2019.
Prior Publication US 2022/0317425 A1, Oct. 6, 2022
Int. Cl. G02B 15/14 (2006.01); G02B 15/16 (2006.01); G02B 13/18 (2006.01)
CPC G02B 15/1461 (2019.08) [G02B 15/14 (2013.01); G02B 15/16 (2013.01); G02B 13/18 (2013.01)] 22 Claims
OG exemplary drawing
 
1. A zoom optical system comprising a plurality of lens groups, wherein
distances between adjacent lens groups among the plurality of lens groups change upon zooming,
the plurality of lens groups include: a first focusing lens group that moves upon focusing; and a second focusing lens group that is disposed closer to an image surface than the first focusing lens group, and moves on a trajectory different from a trajectory of the first focusing lens group upon focusing,
the first focusing lens group and the second focusing lens group each have a negative refractive power,
the first focusing lens group or the second focusing lens group includes at least one lens having a positive refractive power, and
the following conditional expressions are satisfied,
1.40<fFP/(−fFN)<3.50
0.20<βWF1/βWF2<5.00
where
fFP: a focal length of a lens having a strongest positive refractive power among positive lenses in the first focusing lens group and the second focusing lens group,
fFN: a focal length of a lens having a strongest negative refractive power among negative lenses in the first focusing lens group or the second focusing lens group,
βWF1: a lateral magnification of the first focusing lens group upon focusing on an infinity object in a wide angle end state, and
βWF2: a lateral magnification of the second focusing lens group upon focusing on an infinity object in a wide angle end state,
wherein the first focusing lens group moves in a direction toward the image surface upon focusing from an infinity object to a short distant object.