ZOOM LENS AND IMAGING APPARATUS

• US 20150022901A1
• Filed: 10/06/2014
• Published: 01/22/2015
• Est. Priority Date: 04/09/2012
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: KOMATSU, Daiki, CHO, Michio
• Granted Patent: US 9,279,966 B2
• Time in Patent Office: Days
• US Class Current: 359/688
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 15/144109 arranged +--+
• CPC Class Codes: G02B 15/173 arranged +-+
• CPC Class Codes: G02B 27/646 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

Abstract

A zoom-lens substantially consists of a positive-first-lens-group, fixed during magnification-change, a negative-second-lens-group, which moves from object-side toward image-side during magnification change from wide-angle-end to telephoto-end, a negative-third-lens-group, which corrects movement of an image-plane during magnification-change, and a positive-fourth-lens-group, which is fixed during magnification-change and includes a stop, in this order from object-side. The first-lens-group substantially consists of a negative-1a-th-lens-group, fixed during focusing, a positive-1b-th-lens-group, which moves during focusing, and a positive-1c-th-lens-group, fixed during focusing, in this order from object-side. The second-lens-group substantially consists of a negative-2a-th-lens-group and a positive-2b-th-lens-group, and a distance therebetween is changed during magnification-change. The third-lens-group moves in such a manner that a distance from the fourth-lens-group at telephoto-end is narrower than a distance from the fourth-lens-group at wide-angle-end. Predetermined conditional-formulas about a length from a most-object-side surface in the first-lens-group to the stop, a focal-length at wide-angle-end and a focal-length of the 1b-th-lens-group are satisfied.

Claims

1. A zoom lens substantially consisting of:

a first lens group having positive refractive power, and which is fixed during magnification change;

a second lens group having negative refractive power, and which moves from an object side toward an image side while magnification is changed from a wide angle end to a telephoto end;

a third lens group having negative refractive power, and which corrects movement of an image plane during magnification change; and

a fourth lens group having positive refractive power, and which is fixed during magnification change and includes a stop, in this order from the object side,

wherein the first lens group substantially consists of a 1a-th lens group having negative refractive power, and which is fixed during focusing, a 1b-th lens group having positive refractive power, and which moves during focusing, and a 1c-th lens group having positive refractive power, and which is fixed during focusing, in this order from the object side, and

wherein the second lens group substantially consists of a 2a-th lens group having negative refractive power and a 2b-th lens group having positive refractive power in this order from the object side, and a distance between the 2a-th lens group and the 2b-th lens group is changed during magnification change, and

wherein the third lens group moves in such a manner that a distance from the fourth lens group at the telephoto end is narrower than a distance from the fourth lens group at the wide angle end, and

wherein the following conditional formulas (1) and (2) are satisfied;

5.0<

L/fw<

15.0 

 

(1); and

0.050<

fw/f1b<

0.200 

 

(2), where

L;

a length from a most-object-side surface in the first lens group to the stop,

fw;

a focal length at the wide angle end, and

f1b;

a focal length of the 1b-th lens group.

2. The zoom lens, as defined in claim 1, wherein the following conditional formula (1-1) is satisfied:

7.0<

L/fw<

12.0 

 

(1-1), where

L;

a length from a most-object-side surface in the first lens group to the stop, and

fw;

a focal length at the wide angle end.

3. The zoom lens, as defined in claim 1, wherein the following conditional formula (1-2) is satisfied:

8.0<

L/fw<

10.0 

 

(1-2), where

L;

a length from a most-object-side surface in the first lens group to the stop, and

fw;

a focal length at the wide angle end.

4. The zoom lens, as defined in claim 1, wherein a point at which a distance between the 2a-th lens group and the 2b-th lens group is wider than a distance between the 2a-th lens group and the 2b-th lens group at the wide angle end is included in focal length between the wide angle end and the telephoto end.

5. The zoom lens, as defined in claim 1, wherein the following conditional formula (2-1) is satisfied:

0.060<

fw/f1b<

0.150 

 

(2-1), where

fw;

a focal length at the wide angle end, and

f1b;

a focal length of the 1b-th lens group.

6. The zoom lens, as defined in claim 1, wherein the following conditional formula (2-2) is satisfied:

0.070<

fw/f1b<

0.100 

 

(2-2), where

fw;

a focal length at the wide angle end, and

f1b;

a focal length of the 1b-th lens group.

7. The zoom lens, as defined in claim 1, wherein the 1a-th lens group substantially consists of a 1a1-st lens having a negative meniscus lens shape with its convex surface facing the object side, a 1a2-nd lens with its convex surface facing the object side, and the absolute value of the curvature radius of the convex surface of the 1a2-nd lens being smaller than the absolute value of the curvature radius of the other surface of the 1a2-nd lens, and the 1a2-nd lens including an aspherical surface shaped in such a manner that positive refractive power becomes stronger as a distance from an optical axis increases, and a cemented lens of a 1a3-rd lens having negative refractive power, and a concave surface of which faces the object side, and the absolute value of the curvature radius of the concave surface being smaller than the absolute value of the curvature radius of the other surface of the 1a3-rd lens, and a 1a4-th lens having positive refractive power, and a convex surface of which faces the image side, and the absolute value of the curvature radius of the convex surface of the 1a4-th lens being smaller than the absolute value of the curvature radius of the other surface of the 1a4-th lens, in this order from the object side.

8. The zoom lens, as defined in claim 7, wherein the following conditional formula (3) is satisfied:

0.00<

θ

gF1a4−

θ

gF1a3 

 

(3), where

θ

gF1a4;

a partial dispersion ratio of the 1a4-th lens with respect to g-line and F-line, and

θ

gF1a3;

a partial dispersion ratio of the 1a3-rd lens with respect to g-line and F-line.

9. The zoom lens, as defined in claim 1, wherein the 1b-th lens group substantially consists of a cemented lens of a 1b1-st lens having negative refractive power, and a cemented surface of which is convex toward the object side, and a 1b2-nd lens having positive refractive power.

10. The zoom lens, as defined in claim 1, wherein the 2a-th lens group substantially consists of a 2a1-st lens having a negative meniscus lens shape with its convex surface facing the object side and a 2a2-nd lens having a biconcave shape in this order from the object side, and

wherein the 2b-th lens group substantially consists of a cemented lens of a 2bp-th lens having a biconvex shape and a 2bn-th lens having negative refractive power, and a concave surface of which faces the object side, and the absolute value of the curvature radius of the concave surface of the 2bn-th lens being smaller than the absolute value of the curvature radius of the other surface of the 2bn-th lens, in this order from the object side.

11. The zoom lens, as defined in claim 10, wherein the following conditional formula (4) is satisfied:

1.75<

N2a 

 

(4), where

N2a;

an average refractive index of the 2a-th lens group.

12. The zoom lens, as defined in claim 10, wherein the following conditional formula (4-1) is satisfied:

1.83<

N2a 

 

(4-1), where

N2a;

an average refractive index of the 2a-th lens group.

13. The zoom lens, as defined in claim 10, wherein the following conditional formula (5) is satisfied:

20.0<

ν

2bn−

ν

2bp 

 

(5), where

ν

2bn;

an Abbe number of the 2bn-th lens, and

ν

2bp;

an Abbe number of the 2bp-th lens.

14. The zoom lens, as defined in claim 1, wherein the third lens group substantially consists of a cemented lens of a 3n-th lens having a biconcave shape and a 3p-th lens having positive refractive power, and a convex surface of which faces the object side, in this order from the object side.

15. The zoom lens, as defined in claim 14, wherein the following conditional formula (6) is satisfied:

30.0<

ν

3n−

ν

3p 

 

(6), where

ν

3p;

an Abbe number of 3p-th lens L3p, and

ν

3n;

an Abbe number of 3n-th lens L3n.

16. The zoom lens, as defined in claim 14, wherein the following conditional formula (6-1) is satisfied:

40.0<

ν

3n−

ν

3p 

 

(6-1), where

ν

3p;

an Abbe number of 3p-th lens L3p, and

ν

3n;

an Abbe number of 3n-th lens L3n.

17. An imaging apparatus comprising:

the zoom lens, as defined in claim 1, mounted thereon.