| CPC G02B 15/1465 (2019.08) [G02B 3/04 (2013.01); G02B 13/0045 (2013.01)] | 7 Claims |
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1. A zoom lens, comprising:
a first lens group having negative refractive power on a most object side; and
a positive lens group Pa having positive refractive power, a negative lens group N having negative refractive power, and a positive lens group Pb having positive refractive power that are arranged in this order from an object side and provided on an image side with respect to the first lens group, wherein
during zooming from a wide angle end to a telephoto end, the first lens group moves to an image side, the positive lens group Pa and the positive lens group Pb move to an object side along an identical locus, and magnification is varied by changing an interval on an optical axis between adjacent lens groups,
the negative lens group N is moved to an image side to focus on an object at a finite distance from infinity,
following conditions are satisfied:
0.80<(Rnf+Rnr)/(Rnf−Rnr)<1.40 (1)
−1.20<fn/ft<−0.50 (2)
where
Rnf is a curvature radius of a surface of a most object side in the negative lens group N,
Rnr is a curvature radius of a surface of a most image side in the negative lens group N,
fn is a focal length of the negative lens group N, and
ft is a focal length of the zoom lens at a telephoto end,
a following condition is satisfied:
−5.40<(1−βnt2)×βrt2<−2.40 (3)
where
βnt is a lateral magnification at a telephoto end of the negative lens group N, and
βrt is a composite lateral magnification at a telephoto end of all lens groups located on an image side relative to the negative lens group N, and
a following condition is satisfied:
0.70<Ymax/BFw<1.60 (6)
where
Ymax is a maximum image height of the zoom lens, and
BFw is back focus at a wide angle end of the zoom lens at a time of infinity focus.
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