Imaging lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-2016274336-A1
Application number	US-201615067791-A
Country	US
Kind code	A1
Filing date	Mar 11, 2016
Priority date	Mar 16, 2015
Publication date	Sep 22, 2016
Grant date	—

Abstract

An imaging lens is constituted by, 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; and a third lens group having a positive refractive power. The second lens group has at least one positive lens and at least one negative lens. The second lens group moves along the optical axis from the object side to the image side while the first lens group and the third lens group are fixed with respect to an image formation plane to change focus from an object at infinity to an object at a proximal distance. Predetermined Conditional Formulae (1) and (2) are satisfied.

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 second lens group having a negative refractive power; and a third lens group having a positive refractive power; the second lens group having at least one positive lens and at least one negative lens; the second lens group moving along the optical axis from the object side to the image side while the first lens group and the third lens group are fixed with respect to an image formation plane to change focus from an object at infinity to an object at a proximal distance; and Conditional Formulae (1) and (2) below being satisfied:
15<vd_G 2 p<22   (1)

1.0< TL/f< 1.6   (2)

wherein vd_G 2 p is the Abbe's number with respect to the d line of the material of the at least one positive lens within the second lens group, TL is the distance along the optical axis from the lens surface most toward the object side within the first lens group to the image formation plane with back focus as an air converted distance, and f is the focal length of the entire lens system in a state focused on an object at infinity.

2 . 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 second lens group having a negative refractive power; and a third lens group having a positive refractive power; the second lens group having at least one positive lens and at least one negative lens; the entire lens system consisting of at most twelve lenses; the second lens group moving along the optical axis from the object side to the image side while the first lens group and the third lens group are fixed with respect to an image formation plane to change focus from an object at infinity to an object at a proximal distance; and Conditional Formula (1) below being satisfied:
15<vd_G 2 p<22   (1)

wherein vd_G 2 p is the Abbe's number with respect to the d line of the material of the at least one positive lens within the second lens group.

3 . 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 second lens group having a negative refractive power; and a third lens group having a positive refractive power; an aperture stop being positioned at the object side of the second lens group; the second lens group having at least one positive lens and at least one negative lens; the second lens group moving along the optical axis from the object side to the image side while the first lens group and the third lens group are fixed with respect to an image formation plane to change focus from an object at infinity to an object at a proximal distance; and Conditional Formula (1) below being satisfied:
15<vd_G 2 p<22   (1)

wherein vd_G 2 p is the Abbe's number with respect to the d line of the material of the at least one positive lens within the second lens group.

4 . An imaging lens as defined in claim 1 , wherein:
the second lens group consists of a single positive lens and a single negative lens.

5 . An imaging lens as defined in claim 4 , in which Conditional Formula (3) below is satisfied:
48<vd_G 2 n<78   (3)
wherein vd_G 2 n is the Abbe's number with respect to the d line of the material of the negative lens within the second lens group.

6 . An imaging lens as defined in claim 4 , wherein:
the second lens group consists of a cemented lens formed by cementing a single positive lens and a single negative lens together.

7 . An imaging lens as defined in claim 1 , wherein:
the first lens group to has at least two positive lenses; and Conditional Formula (4) below is satisfied:
58<vd_G 1 pa   (4)

wherein vd_G 1 pa is the average Abbe's number with respect to the d line of the materials of the positive lenses within the first lens group.

8 . An imaging lens as defined in claim 1 , wherein
the first lens group to has at least two positive lenses that satisfy both of Conditional Formulae (5) and (6) below:
60<vd_G 1 p   (5)

0.004< θgF _G 1 p+0.00162 vd _ G 1 p− 0.6415   (6)

wherein vd_G 1 p is the Abbe's number with respect to the d line of the materials of the positive lenses within the first lens group, and θgF_G 1 p is the partial dispersion ratio between the g line and the F line of the positive lenses within the first lens group.

9 . An imaging lens as defined in claim 1 , wherein:
the third lens group has at least one positive lens that satisfies both of Conditional Formulae (7) and (8) below:
60<vd_G 3 p   (7)

0.004< θgF _G 3 p+0.00162 vd _G 3 p−0.6415   (8)

wherein vd_G 3 p is the Abbe's number with respect to the d line of the material of the at least one positive lens within the third lens group, and θgF_G 3 p is the partial dispersion ratio between the g line and the F line of the positive lens within the third lens group.

10 . An imaging lens as defined in claim 1 , wherein:
the first lens group has at least one negative lens that satisfies Conditional Formula (9) below:
30<vd_G 1 n<40   (9)

wherein vd_G 1 n is the Abbe's number with respect to the d line of the material of the at least one negative lens within the first lens group.

11 . An imaging lens as defined in claim 1 , wherein:
the first lens group has at least three positive lenses and at least one negative lens.

12 . An imaging lens as defined in claim 1 , wherein:
the first lens group consists of three positive lenses and one negative lens.

13 . An imaging lens as defined in claim 1 , wherein:
the third lens group has at least two positive lenses and at least two negative lenses; and the third lens group as a whole consists of at most five lenses.

14 . An imaging lens as defined in claim 1 , wherein:
the third lens group has a lens component having a negative refractive power at the most image side within the third lens group.

15 . An imaging lens as defined in claim 14 , wherein:
the third lens group has a single lens having a negative refractive power at the most image side within the third lens group; and the single lens satisfies Conditional Formula (10) below:
40<vd_G 3 nr   (10)

wherein vd_G 3 nr is the Abbe's number with respect to the d line of the single lens having a negative refractive power positioned most toward the image side within the third lens group.

16 . An imaging lens as defined in claim 14 , wherein:
the third lens group has a single lens having a negative refractive power at the most image side within the third lens group, and a single lens having a positive refractive power positioned adjacent to the single lens having a negative refractive power at the object side thereof.

17 . An imaging lens as defined in claim 1 , in which Conditional Formula (11) below is satisfied:
0.3< |f 2 |/f< 0.8   (11)
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.

18 . An imaging lens as defined in claim 1 , wherein:
an aperture stop is positioned at the image side of the lens surface most toward the object side within the first lens group; and a filter, of which the transmissivity decreases as the distance from the optical axis increases, is positioned adjacent to the aperture stop at one of the object side and the image side thereof.

19 . An imaging apparatus equipped with an imaging lens as defined in cl

Assignees

• Fujifilm Corp

Inventors

• Kawamura Daiki

Classifications

• G02B13/02 Primary

  Telephoto objectives, i.e. systems of the type + - in which the distance from the front vertex to the image plane is less than the equivalent focal length · CPC title

• G02B27/0025

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

• G02B13/0015

  characterised by the lens design · CPC title

• G02B13/006

  at least one element being a compound optical element, e.g. cemented elements · CPC title

• G02B15/173 Primary

  arranged +-+ · CPC title