Zoom lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-2016124200-A1
Application number	US-201514829976-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 zoom lens includes sequentially from an object side a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a negative refractive power; and a fourth lens group having a negative refractive power. The first lens group, the second lens group, the third lens group, and the fourth lens group are moved along an optical axis to zoom from a wide angle end to telephoto end and such that an interval between the first lens group and the second lens group decreases and distances that the second lens group and the fourth lens group are moved are equivalent. The third lens group is moved along the optical axis, toward an image side to focus from a focused state at infinity to a focused state at a minimum object distance.

First claim

What is claimed is:

1 . A zoom lens comprising sequentially from an object side:
a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a negative refractive power; and a fourth lens group having a negative refractive power, wherein the first lens group, the second lens group, the third lens group, and the fourth lens group are moved along an optical axis to zoom from a wide angle end to telephoto end and such that an interval between the first lens group and the second lens group decreases and distances that the second lens group and the fourth lens group are moved are equivalent, and the third lens group is moved along the optical axis, toward an image side to focus from a focused state at infinity to a focused state at a minimum object distance.

2 . The zoom lens according to claim 1 , wherein
the zoom lens satisfies a conditional expression (1) 1.06≦β4T≦3.00, where, β4T represents lateral magnification of the fourth lens group at the telephoto end.

3 . The zoom lens according to claim 1 , wherein the zoom lens satisfies a conditional expression (2)

1.20
≤



f



4



(

fw
×
f



t

)

≤
10.00

where, f4 represents a focal length of the fourth lens group, fw represents a focal length of the entire optical system at the wide angle end, and ft represents the focal length of the entire optical system at the telephoto end.

4 . The zoom lens according to claim 1 , wherein
the zoom lens satisfies a conditional expression (3)

0.70
≤



f



3



(

fw
×
f



t

)

≤
5.00

where, f3 represents a focal length of the third lens group, fw represents the focal length of the entire optical system at the wide angle end, and ft represents the focal length of the entire optical system at the telephoto end.

5 . The zoom lens according to claim 1 , wherein
the second lens group has a stabilizing group that is moved in a direction that is substantially orthogonal to the optical axis and corrects blur, and the zoom lens satisfies a conditional expression (4)

0.30
≤

fv

(

fw
×
f



t

)

≤
1.10

wherein, fv represents a focal length of the stabilizing group, fw represents the focal length of the entire optical system at the wide angle end, and ft represents the focal length of the entire optical system at the telephoto end.

6 . An imaging apparatus comprising:
a zoom lens; and an image sensor configured to convert an optical image formed by the zoom lens into an electrical signal, wherein the zoom lens includes sequentially from an object side:
a first lens group having a negative refractive power;
a second lens group having a positive refractive power;
a third lens group having a negative refractive power; and
a fourth lens group having a negative refractive power,
the first lens group, the second lens group, the third lens group, and the fourth lens group are moved along an optical axis to zoom from a wide angle end to telephoto end and such that an interval between the first lens group and the second lens group decreases and distances that the second lens group and the fourth lens group are moved are equivalent, and the third lens group is moved along the optical axis, toward an image side to focus from a focused state at infinity to a focused state at a minimum object distance.

Assignees

• Tamron Kk

Inventors

• Obikane Yasuhiko
• Yokota Koichiro

Classifications

• H04N5/23296

  Electricity · mapped topic

• G02B15/20 Primary

  having an additional movable lens or lens group for varying the objective focal length · CPC title

• G02B27/0025

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

• G02B27/646

  compensating for small deviations, e.g. due to vibration or shake (movement of one or more optical elements for control of motion blur in cameras, projectors or printers G03B2205/0007; image stabilisation in cameras peculiar to the presence or use of an electronic image sensor H04N23/68) · CPC title

• G02B15/177

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