Patent ID: 11880023
Assignee: TAMRON CO., LTD.
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A zoom lens comprising, sequentially from an object side:
a first lens group having negative refractive power;
a second lens group having positive refractive power; and
a lens group having positive refractive power on an image side of the second lens group,
the zoom lens performing a magnification change operation by changing a gap between the adjacent lens groups, wherein
the second lens group includes a lens Lp having positive refractive power, and
the zoom lens satisfies following expressions (1) to (5):

0.85<f2/f2p<1.50  (1)

0<f2/fw<3.25  (2)

−0.30<ΔPdt_2p<−0.10  (3)

1.50<Nd2<2.00  (4)

where
f2 is a focal length of the second lens group,
f2p is a focal length of the lens Lp,
fw is a focal length at a wide angle end of the zoom lens in infinity focus,
ΔPdt_2p is an extraordinary dispersion property between a d line and a t line of the lens Lp, and
Nd2 is a refractive index of the lens Lp at the d line.