US 12,276,781 B2
Zoom optical system, optical apparatus, imaging 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. 21, 2022, as Appl. No. 17/580,918.
Application 17/580,918 is a division of application No. 16/345,198, granted, now 11,269,164, previously published as PCT/JP2016/084396, filed on Nov. 21, 2016.
Prior Publication US 2022/0146800 A1, May 12, 2022
Int. Cl. G02B 15/14 (2006.01); G02B 15/20 (2006.01); G02B 27/64 (2006.01); G02B 9/34 (2006.01); G02B 9/60 (2006.01); G02B 9/62 (2006.01); G02B 9/64 (2006.01)
CPC G02B 15/144105 (2019.08) [G02B 15/20 (2013.01); G02B 27/646 (2013.01); G02B 9/34 (2013.01); G02B 9/60 (2013.01); G02B 9/62 (2013.01); G02B 9/64 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A zoom optical system comprising, in order from an object:
a front lens group having a positive refractive power;
an M1 lens group having a negative refractive power;
an M2 lens group having a positive refractive power; and
an RN lens group having a negative refractive power,
wherein upon zooming, a lens group nearest to the object in the M1 lens group is fixed with respect to an image surface, a distance between the front lens group and the M1 lens group changes, a distance between the M1 lens group and the M2 lens group changes, and a distance between the M2 lens group and the RN lens group changes,
upon zooming from a wide-angle end state to a telephoto end state, the front lens group moves toward the object,
upon focusing from an infinite distant object to a short distant object, the RN lens group moves, and
the following conditional expressions are satisfied,
0.25<(−fF)/f1<0.45
0.20<fTM2/f1≤0.298
1.80<f1/fw<3.50
where
fF: a focal length of the RN lens group,
f1: a focal length of the front lens group,
fTM2: a focal length of the M2 lens group in the telephoto end state, and
fw: a focal length of the zoom optical system in the wide-angle end state.