Imaging lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-2016356986-A1
Application number	US-201615157713-A
Country	US
Kind code	A1
Filing date	May 18, 2016
Priority date	Jun 8, 2015
Publication date	Dec 8, 2016
Grant date	—

Abstract

An imaging lens is constituted by, in order from the object side to the image side: a positive first lens group; a stop; a negative second lens group; and a positive third lens group. Only the second lens group moves in the direction of the optical axis to perform focusing operations. The second lens group is constituted by one or two positive lenses and one negative lens. The third lens group is constituted by, in order from the object side to the image side, two or three positive lenses and one negative lens.

First claim

What is claimed is:

1 . An imaging lens consisting of, in order from the object side to the image side:
a first lens group having a positive refractive power; a stop; a second lens group having a negative refractive power; and a third lens group having a positive refractive power; only the second lens group moving in the direction of the optical axis to perform focusing operations; the second lens group consisting of one or two positive lenses and one negative lens; and the third lens group consisting of, in order from the object side to the image side, two or three positive lenses and one negative lens.

2 . An imaging lens as defined in claim 1 , in which Conditional Formula (14) below is satisfied:
0.6 <f 3/ f< 1.2   (14)
wherein f3 is the focal length of the third lens group, and f is the focal length of the entire lens system in a state focused on an object at infinity.

3 . An imaging lens as defined in claim 1 , in which Conditional Formula (8) below is satisfied:
0.4 <−f 2/ f< 1.3   (8)
wherein f2 is the focal length of the second lens group, and f is the focal length of the entire lens system in a state focused on an object at infinity.

4 . An imaging lens as defined in claim 1 , in which Conditional Formula (15) below is satisfied:
0.5 <f 1/ f 3<1.2   (15)
wherein f1 is the focal length of the first lens group, and f3 is the focal length of the third lens group.

5 . An imaging lens as defined in claim 1 , in which Conditional Formulae (10) and (11) below are satisfied:
1.65<NG2n<2.2   (10)
28<νG2n< 60   (11)
wherein NG2n is the refractive index with respect to the d line of the negative lens within the second lens group, and νG2n is the Abbe's number with respect to the d line of the negative lens within the second lens group.

6 . An imaging lens as defined in claim 1 , in which Conditional Formula (12) below is satisfied:
−0.3<( RG 2 nf+RG 2 nr )/( RG 2 nf−RG 2 nr )<1.8   (12)
wherein RG2nf is the radius of curvature of the surface toward the object side of the negative lens within the second lens group, and RG2nr is the radius of curvature of the surface toward the image side of the negative lens within the second lens group.

7 . An imaging lens as defined in claim 1 , in which Conditional Formula (16) below is satisfied:
−0.5<( RG 3 nf+RG 3 nr )/( RG 3 nf−RG 3 nr )<10   (16)
wherein RG3nf is the radius of curvature of the surface toward the object side of the negative lens within the third lens group, and RG3nr is the radius of curvature of the surface toward the image side of the negative lens within the third lens group.

8 . An imaging lens as defined in claim 1 , wherein:
the negative lens within the third lens group is a meniscus lens having a concave surface toward the image side.

9 . An imaging lens as defined in claim 1 , wherein:
the first lens group consists of eight or fewer lenses.

10 . An imaging lens as defined in claim 2 , in which Conditional Formula (14-1) below is satisfied:
0.7 <f 3/ f< 1.1   (14-1)

11 . An imaging lens as defined in claim 3 , in which Conditional Formula (8-1) below is satisfied:
0.5 <−f 2/ f <1.2   (8-1)

12 . An imaging lens as defined in claim 4 , in which Conditional Formula (15-1) below is satisfied:
0.6 <f 1/ f 3<1.1   (15-1)

13 . An imaging lens as defined in claim 5 , in which Conditional Formula (10-1) is satisfied:
1.7<NG2n<2.1   (10-1)

14 . An imaging lens as defined in claim 5 , in which Conditional Formula (11-1) is satisfied:
30<νG2n<55   (11-1)

15 . An imaging lens as defined in claim 6 , in which Conditional Formula (12-1) below is satisfied:
−0.2<( RG 2 nf+RG 2 nr )/( RG 2 nf−RG 2 nr )<1.5   (12-1)

16 . An imaging lens as defined in claim 7 , in which Conditional Formula (16-1) below is satisfied:
−0.3<( RG 3 nf+RG 3 nr )/( RG 3 nf−RG 3 nr )<9   (16-1)

17 . An imaging apparatus equipped with an imaging lens as defined in claim 1 .

Assignees

• Fujifilm Corp

Inventors

• Sun Ping

Classifications

• G02B13/18

  with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)} · CPC title

• G02B13/0035

  having three lenses · CPC title

• G02B9/12

  having three components only · CPC title

• G02B13/16

  for use in conjunction with image converters or intensifiers {, or for use with projectors, e.g. objectives for projection TV} · 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