Wide angle zoom lens

Patent metadata

Field	Value
Publication number	US-2016124181-A1
Application number	US-201514830011-A
Country	US
Kind code	A1
Filing date	Aug 19, 2015
Priority date	Oct 31, 2014
Publication date	May 5, 2016
Grant date	—

Abstract

A wide angle zoom lens includes sequentially from the object side, a first lens group having a negative refractive power overall and three lenses, including first to third lenses, having a negative refractive power and disposed farthest on the object side; a second lens group having a positive refractive power overall and one or more sets of cemented lenses; and a third lens group having a negative refractive power. This ultra wide angle zoom lens varies intervals between the first lens group, the second lens group, and the third lens group on the optical axis to zoom from the wide angle end to the telephoto end and satisfies given conditions to thereby enable a high zoom ratio, large diameter, and high resolution.

First claim

What is claimed is:

1 . A wide angle zoom lens comprising sequentially from an object side:
a first lens group having a negative refractive power overall and three lenses, including a first lens, a second lens, and a third lens, successively disposed farthest on the object side and having a negative refractive power; a second lens group having a positive refractive power overall and one or more sets of cemented lenses; and a third lens group, wherein the wide angle zoom lens zooms from a wide angle end to a telephoto end by varying intervals between the first lens group, the second lens group, and the third lens group on the optical axis, and the wide angle zoom lens satisfies a conditional expression (1) 70≦υmax2a≦99 and a conditional expression (2) 70≦υmaxg23≦99, where υmax2a represents an Abbe number of a lens that among the one or more sets of cemented lenses included in the second lens group, has least dispersion, and υmaxg23 represents an Abbe number of a lens that among the second lens and the third lens included in the first lens group, has lesser dispersion.

2 . A wide angle zoom lens comprising sequentially from an object side:
a first lens group having a negative refractive power overall and three lenses, including a first lens, a second lens, and a third lens, successively disposed farthest on the object side and having a negative refractive power; a second lens group having a positive refractive power overall and one or more sets of cemented lenses; and a third lens group, wherein the wide angle zoom lens zooms from a wide angle end to a telephoto end by varying intervals between the first lens group, the second lens group, and the third lens group on the optical axis, and the wide angle zoom lens satisfies a conditional expression (1) 70≦υmax2a≦99 and a conditional expression (3) −10≦fg1/fw≦−2.4, where υmax2a represents an Abbe number of a lens that among the one or more sets of cemented lenses included in the second lens group, has least dispersion, fg1 represents a composite focal length of the first lens group, and fw represents an optical system focal length at the wide angle end.

3 . The wide angle zoom lens according to claim 1 , wherein
the wide angle zoom lens satisfies a conditional expression (4) −6≦f123/fw≦−1, where f123 represents a composite focal length of the first lens, the second lens, and the third lens included in the first lens group and fw represents an optical system focal length at the wide angle end.

4 . The wide angle zoom lens according to claim 1 , wherein
the third lens group includes one negative lens, and the wide angle zoom lens satisfies a conditional expression (5) −0.73≦ft/f3gn≦−0.22, where f3gn represents a focal length of the one negative lens and ft represents an optical system focal length at the telephoto end.

5 . The wide angle zoom lens according to claim 1 , wherein
one or more positive lenses are disposed in or subsequent to the third group, and the wide angle zoom lens satisfies a conditional expression (6) 0≦ft/f3gp≦0.33, where f3gp represents a focal length of a positive lens that among the one or more positive lenses, has a refractive power that is strongest and ft represents an optical system focal length at the telephoto end.

6 . The wide angle zoom lens according to claim 1 , wherein
the wide angle zoom lens satisfies a conditional expression (7) 0.5≦(ΔD2/Y)×(fw/ft)≦2.9, where ΔD2 represents a distance that the second lens group is moved during zooming from the wide angle end to the telephoto end, Y represents a maximum image height, fw represents an optical system focal length at the wide angle end, and ft represents the optical system focal length at the telephoto end.

7 . The wide angle zoom lens according to claim 1 , wherein
the wide angle zoom lens satisfies a conditional expression (8) 1.70≦N1≦2.1, where N1 represents a refractive index corresponding to d-line of the first lens included in the first lens group.

8 . The wide angle zoom lens according to claim 2 , wherein
the wide angle zoom lens satisfies a conditional expression (4) −6≦f123/fw≦−1, where f123 represents a composite focal length of the first lens, the second lens, and the third lens included in the first lens group and fw represents the optical system focal length at the wide angle end.

9 . The wide angle zoom lens according to claim 2 , wherein
the third lens group includes one negative lens, and the wide angle zoom lens satisfies a conditional expression (5) −0.73≦ft/f3gn≦−0.22, where f3gn represents a focal length of the one negative lens and ft represents the optical system focal length at the telephoto end.

10 . The wide angle zoom lens according to claim 2 , wherein
one or more positive lenses are disposed in or subsequent to the third group, and the wide angle zoom lens satisfies a conditional expression (6) 0≦ft/f3gp≦0.33, where f3gp represents a focal length of a positive lens that among the one or more positive lenses, has a refractive power that is strongest and ft represents the optical system focal length at the telephoto end.

11 . The wide angle zoom lens according to claim 2 , wherein
the wide angle zoom lens satisfies a conditional expression (7) 0.5≦(ΔD2/Y)×(fw/ft)≦2.9, where ΔD2 represents a distance that the second lens group is moved during zooming from the wide angle end to the telephoto end, Y represents a maximum image height, fw represents the optical system focal length at the wide angle end, and ft represents the optical system focal length at the telephoto end.

12 . The wide angle zoom lens according to claim 2 , wherein
the wide angle zoom lens satisfies a conditional expression (8) 1.70≦N1≦2.1, where N1 represents a refractive index corresponding to d-line of the first lens included in the first lens group.

Assignees

• Tamron Kk

Inventors

• Noda Takayuki
• Mitsuhashi Takahiro
• Nakai Seigou

Classifications

• G02B15/177

  having a negative front lens or group of lenses · CPC title

• G02B13/009 Primary

  having zoom function · CPC title

• G02B27/0025

  for optical correction, e.g. distorsion, aberration · CPC title

• G02B13/006

  at least one element being a compound optical element, e.g. cemented elements · CPC title

• G02B15/143503

  arranged -+- · CPC title