Zoom lens system, imaging optical device, and digital appliance

Patent metadata

Field	Value
Publication number	US-9256059-B2
Application number	US-201314414383-A
Country	US
Kind code	B2
Filing date	Jul 4, 2013
Priority date	Jul 10, 2012
Publication date	Feb 9, 2016
Grant date	Feb 9, 2016

Abstract

A zoom lens system having a negative first lens group and a positive second lens group, from an object side, and achieving zooming by varying a group-to-group distance. The second lens group includes a three-element cemented lens which is a set of three lens elements cemented together including, from the object side, a negative first lens, a positive second lens, and a negative third lens, and the three-element cemented lens fulfills conditional formulas 0.08<(rs 2 +rs 1 )/(rs 2 −rs 1 )<0.5, 27<v 2 -v 1 <40, 20<v 2 -v 3 <38 (rs 1 , rs 2 represent the curvature radius of the sides of cemented surfaces of the three-element cemented lens on the object side and the image side respectively, and v 1 - 3 represent the Abbe numbers of the first to third lenses of the three-element cemented lens).

First claim

The invention claimed is:

1. A zoom lens system comprising, from an object side,
a first lens group having a negative optical power; and
a second lens group having a positive optical power,
the zoom lens system achieving zooming by varying a group-to-group distance,
wherein
the second lens group includes at least one three-element cemented lens which is a set of three lens elements cemented together including, from the object side, a first lens element having a negative optical power, a second lens element having a positive optical power, and a third lens element having a negative optical power, and
the three-element cemented lens fulfills conditional formulas (1) to (3) below:
0.08<( rs 2 +rs 1)/( rs 2 −rs 1)<0.5  (1)

27 <v 2 −v 1 <40  (2)

20 <v 2 −v 3 <38  (3)

where
rs 1 represents a radius of curvature of an object-side cemented surface of the three-element cemented lens;
rs 2 represents a radius of curvature of an image-side cemented surface of the three-element cemented lens;
v 1 represents an Abbe number of the first lens element of the three-element cemented lens;
v 2 represents an Abbe number of the second lens element of the three-element cemented lens;
v 3 represents an Abbe number of the third lens element of the three-element cemented lens.

2. The zoom lens system according to claim 1 , wherein the first and second lens groups fulfill conditional formula (4) below:
0.8 <f 1 /f 2<−0.5  (4)

where
f 1 represents a focal length of the first lens group; and
f 2 represents a focal length of the second lens group.

3. The zoom lens system according to claim 1 , wherein the second lens group
includes, from the object side, a front group, an aperture stop, and a rear group,
includes the three-element cemented lens in the rear group, and
fulfills conditional formula (5) below:
1 <fs/f 2 — r <−0.3  (5)

where
f 2 _r represents a focal length of the rear group of the second lens group; and
fs represents a focal length of the three-element cemented lens in the second lens group.

4. The zoom lens system according to claim 1 ,
wherein the first lens group includes two composite aspherical surfaces that fulfill conditional formula (6) below:
4.8 <ΔX _max/ ΔX _min<6.0  (6)

where, with respect to thickness, in an optical axis direction, of resin forming the composite aspherical surfaces,
ΔX_max represents a maximum resin thickness; and
ΔX_min represents a minimum resin thickness.

5. The zoom lens system according to claim 1 4 , wherein
the second lens group includes, from the object side, a front group, an aperture stop, and a rear group, and
the rear group includes three lens components comprising a positive, a negative, and a positive lens component which are each a single or cemented lens element.

6. An imaging optical device comprising:
the zoom lens system according to claim 1 and
an image sensor for converting an optical image formed on a light-receiving surface into an electrical signal, the zoom lens system being arranged such that an optical image of a subject is formed on the light-receiving surface of the image sensor.

7. A digital appliance comprising the imaging optical device according to claim 6 so as to have at least one of a function of shooting a still image of the subject or a function of shooting a moving image of the subject.

Assignees

• Konica Minolta Inc
• Nikon Corp

Inventors

• Inoue Kana
• Terada Mamoru
• Sato Haruo

Classifications

• H04N23/69

  Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming · CPC title

• H04N5/23296

  Electricity · mapped topic

• G02B13/04

  Reversed telephoto objectives · CPC title

• G02B15/177 Primary

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

• G02B15/161

  Physics · mapped topic