Zoom lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-2016154222-A1
Application number	US-201514953098-A
Country	US
Kind code	A1
Filing date	Nov 27, 2015
Priority date	Dec 2, 2014
Publication date	Jun 2, 2016
Grant date	—

Abstract

A zoom lens is constituted by, in order from the object side: a positive first lens group; a negative second lens group; a positive third lens group; a negative fourth lens group; and a positive fifth lens group. The distance between the first and second lens groups constantly increases, the distance between the second and third lens groups constantly decreases, the distance between the third and fourth lens groups constantly changes, and the distance between the fourth and fifth lens groups constantly increases when changing magnification from the wide angle end to the telephoto end. The first lens group is constituted by three lenses, which are negative, positive, and positive in order from the object side. The second lens group is constituted by five lenses, which are negative, negative, positive, positive, and negative in order from the object side. The fifth lens group is constituted by a single lens component.

First claim

What is claimed is:

1 . A zoom lens consisting of, in order from the object side to the image side:
a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; a fourth lens group having a negative refractive power; and a fifth lens group having a positive refractive power; the distance between the first lens group and the second lens group constantly increasing, the distance between the second lens group and the third lens group constantly decreasing, the distance between the third lens group and the fourth lens group constantly changing, and the distance between the fourth lens group and the fifth lens group constantly increasing when changing magnification from the wide angle end to the telephoto end; the first lens group consisting of, in order from the object side to the image side, a 1-1 negative lens, a 1-2 positive lens, and a 1-3 positive lens; the second lens group consisting of, in order from the object side to the image side, a 2-1 negative meniscus lens having a concave surface toward the image side, a 2-2 negative lens, a 2-3 positive lens, a 2-4 positive lens, and a 2-5 negative lens; and the fifth lens group consisting of a single lens component.

2 . A zoom lens as defined in claim 1 , in which Conditional Formula (1) below is satisfied:
−0.9<( L 11 f−L 12 r )/( L 11 f+L 12 r )<−0.1  (1)
wherein L11f is the paraxial radius of curvature of the surface of the 1-1 negative lens toward the object side, and L12r is the paraxial radius of curvature of the surface of the 1-2 positive lens toward the image side.

3 . A zoom lens as defined in claim 1 , wherein:
the third lens group consists of four positive lenses, two negative lenses, and an aperture stop.

4 . A zoom lens as defined in claim 1 , wherein:
the third lens group consists of, in order from the object side to the image side, a 3-1 positive lens, an aperture stop, a 3-2 cemented lens having a positive combined refractive power, a 3-3 cemented lens having a negative combined refractive power, and a 3-4 positive lens.

5 . A zoom lens as defined in claim 4 , wherein:
the 3-2 cemented lens is formed by cementing a negative lens and a biconvex lens, provided in this order from the object side to the image side, together.

6 . A zoom lens as defined in claim 4 , wherein:
the 3-3 cemented lens is formed by cementing a positive lens having a convex surface toward the image side and a biconcave lens, provided in this order from the object side to the image side, together.

7 . A zoom lens as defined in claim 1 , in which Conditional Formula (2) below is satisfied:
0.15< f 2/ L 22 f< 1  (2)
wherein f2 is the paraxial focal length of the second lens group with respect to the d line, and L22f is the paraxial radius of curvature of the surface of the 2-2 negative lens toward the object side.

8 . A zoom lens as defined in claim 1 , in which Conditional Formula (3) below is satisfied:
0.6< f 2/ f 21<1.3  (3)
wherein f2 is the paraxial focal length of the second lens group with respect to the d line, and f21 is the paraxial focal length of the 2-1 negative lens with respect to the d line.

9 . A zoom lens as defined in claim 4 , in which Conditional Formula (4) below is satisfied:
0.7< f 3/ f 34<1.6  (4)
wherein f3 is the paraxial focal length of the third lens group with respect to the d line, and f34 is the paraxial focal length of the 3-4 positive lens with respect to the d line.

10 . A zoom lens as defined in claim 4 , in which Conditional Formula (5) below is satisfied:
0.2< f 3/ f 31<1.5  (5)
wherein f3 is the paraxial focal length of the third lens group with respect to the d line, and f31 is the paraxial focal length of the 3-1 positive lens with respect to the d line.

11 . A zoom lens as defined in claim 1 , wherein:
the fifth lens group is fixed with respect to an imaging surface when changing magnification.

12 . A zoom lens as defined in claim 1 , wherein:
the fifth lens group consists of a single lens; and Conditional Formula (6) below is satisfied:
15<ν d 5<40  (6)

wherein νd5 is the Abbe's number of the single lens with respect to the d line.

13 . A zoom lens as defined in claim 4 , in which Conditional Formula (7) below is satisfied:
20<ν d 31<40  (7)
wherein νd31 is the Abbe's number of the 3-1 positive lens with respect to the d line.

14 . A zoom lens as defined in claim 1 , wherein:
only the fourth lens group is moved to perform focusing operations.

15 . A zoom lens as defined in claim 1 , in which Conditional Formula (1-1) below is satisfied:
−0.5<( L 11 f−L 12 r )/( L 11 f+L 12 r )<−0.12  (1-1)
wherein L11f is the paraxial radius of curvature of the surface of the 1-1 negative lens toward the object side, and L12r is the paraxial radius of curvature of the surface of the 1-2 positive lens toward the image side.

16 . A zoom lens as defined in claim 1 , in which Conditional Formula (3-1) below is satisfied:
0.7< f 2/ f 21<1.1  (3-1)
wherein f2 is the paraxial focal length of the second lens group with respect to the d line, and f21 is the paraxial focal length of the 2-1 negative lens with respect to the d line.

17 . A zoom lens as defined in claim 9 , in which Conditional Formula (4-1) below is satisfied:
0.9< f 31 f 34<1.5  (4-1)
wherein f3 is the paraxial focal length of the third lens group with respect to the d line, and f34 is the paraxial focal length of the 3-4 positive lens with respect to the d line.

18 . A zoom lens as defined in claim 1 , wherein:
the fifth lens group consists of a single lens; and Conditional Formula (6-1) below is satisfied:
16<ν d 5<38  (6-1)

wherein νd5 is the Abbe's number of the single lens with respect to the d line.

19 . A zoom lens as defined in claim 13 , in which Conditional Formula (7-1) below is satisfied:
25<ν d 31<35  (7-1)
wherein νd31 is the Abbe's number of the 3-1 positive lens with respect to the d line.

20 . An imaging apparatus equipped with the zoom lens as defined in claim 1 .

Assignees

• Fujifilm Corp

Inventors

• Noda Taiga
• Tomioka Ryoko
• Cho Michio

Classifications

• G02B15/20

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

• G02B15/16 Primary

  with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group (G02B15/22 takes precedence) · 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

• G02B15/14

  by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective · CPC title

• G02B27/0025

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