Zoom lens and image capturing apparatus

• US 8,879,163 B2
• Filed: 04/10/2013
• Issued: 11/04/2014
• Est. Priority Date: 05/23/2012
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Oohata, Atsushi, Hagiwara, Hiroki
• Primary Examiner(s): Lester, Evelyn A.
• Application Number:
  US13/860,205
• Publication Number:
  US 20130314585A1
• Time in Patent Office: 573 Days
• Field of Search: 359/680, 359682-686, 359/715, 359/740, 359/453, 359/783
• US Class Current: 359/680
• CPC Class Codes: G02B 13/009 having zoom function
• CPC Class Codes: G02B 15/144515 arranged -+++

Abstract

There is provided a zoom lens including, in order from an object side to an image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power. In zooming from a wide-angle end to a telescopic end, the first lens group moves to the object side in a manner that a distance toward the second lens group shortens, and a distance between the third lens group and the fourth lens group lengthens. The third lens group includes a single lens or a single cemented lens.

Claims

1. A zoom lens comprising:

in order from an object side to an image side,

a first lens group having negative refractive power;

a second lens group having positive refractive power;

a third lens group having positive refractive power; and

a fourth lens group having positive refractive power,

wherein, in zooming from a wide-angle end to a telescopic end, the first lens group moves to the object side in a manner that a distance toward the second lens group shortens, and a distance between the third lens group and the fourth lens group lengthens,

wherein the third lens group includes a single lens or a single cemented lens, and

wherein the following conditional expressions (a) and (b) are satisfied,

Δ

m3/(fw×

ft)^1/2<

0.2 

 

conditional expression (a);

d23_max/(fw×

ft)^1/2<

0.4 

 

conditional expression (b);

where

Δ

m3;

a variation amount of a distance between the second lens group and the third lens group in varying magnification,

d23_max;

a maximum value of the distance between the second lens group and the third lens group in varying magnification,

fw;

a system focal length at the wide-angle end, and

ft;

a system focal length at the telescopic end.

2. The zoom lens according to claim 1,

wherein the second lens group includes, in order from the object side, three lenses of a first positive lens, a second positive lens and a negative lens, and

wherein the second positive lens and the negative lens are joined with each other.

3. The zoom lens according to claim 1,

wherein the third lens group satisfies the following conditional expression (c),

0.8<

f3g/ft<

3.5 

 

conditional expression (c);

where

f3g;

a focal length of the third lens group.

4. The zoom lens according to claim 1,

wherein vibration isolation is performed by moving the third lens group perpendicularly to an optical axis.

5. The zoom lens according to claim 1, comprising:

an aperture stop disposed on the second lens group or the third lens group; and

a light shielding member shielding a circumferential light ray on a part of the third lens group at the wide-angle end,

wherein the following conditional expression (d) is satisfied,

L×

Fno_—

w/(fw×

ft)^1/2<

2.5 

 

conditional expression (d);

where

L;

a distance along an optical axis between the aperture stop and the light shielding member at the wide-angle end, and

Fno_w;

an F value at the wide-angle end.

6. The zoom lens according to claim 1,

wherein the third lens group includes a single lens made of a resin.

7. The zoom lens according to claim 1,

wherein lenses at least each one of which is included in each of the first to fourth lens groups and has power whose plus or minus sign is identical with a plus or minus sign of the power of the corresponding lens group are non-spherical,

wherein an opening aperture stop is disposed on the object side of the second lens group,

wherein a surface of the second lens group closest to the object side and a surface of the third lens group on the image side are non-spherical, and

wherein a circumferential light ray at the wide-angle end is shielded on the surface of the third lens group on the mage side.

8. An image capturing apparatus comprising:

a zoom lens including, in order from an object side to an image side,

a first lens group having negative refractive power,

a second lens group having positive refractive power,

a third lens group having positive refractive power, and

a fourth lens group having positive refractive power; and

an image sensor converting an optical image formed by the zoom lens into an electric signal,

wherein, in zooming from a wide-angle end to a telescopic end, the first lens group moves to the object side in a manner that a distance toward the second lens group shortens, and a distance between the third lens group and the fourth lens group lengthens,

wherein the third lens group includes a single lens or a single cemented lens, and

wherein the following conditional expressions (a) and (b) are satisfied,

Δ

m3/(fw×

ft)^1/2<

0.2 

 

conditional expression (a);

d23_max/(fw×

ft)^1/2<

0.4 

 

conditional expression (b);

where

Δ

m3;

a variation amount of a distance between the second lens group and the third lens group in varying magnification,

d23_max;

a maximum value of the distance between the second lens group and the third lens group in varying magnification,

fw;

a system focal length at the wide-angle end, and

ft;

a system focal length at the telescopic end.