Imaging lens and imaging apparatus equipped with the same

Patent metadata

Field	Value
Publication number	US-9615008-B2
Application number	US-201514732908-A
Country	US
Kind code	B2
Filing date	Jun 8, 2015
Priority date	Dec 26, 2012
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

An imaging lens consists of a front group having a positive refractive power, a stop, and a rear group having a positive refractive power. The front group is composed of a front group negative lens group constituted by two or more negative lenses and a front group positive lens group constituted by a plurality of lenses with a positive lens being disposed on the most object side to have a positive refractive power, in order from the object side. The rear group includes at least one negative lens. When the Abbe number of the most object side positive lens in the front group positive lens group with respect to the d-line is taken as νp, the imaging lens satisfies a conditional expression (1): νp<30.

First claim

What is claimed is:

1. An imaging lens, consisting of a front group having a positive refractive power, a stop, and a rear group having a positive refractive power, in order from the object side, wherein:
the front group is composed of a front group negative lens group composed of two negative lenses and a front group positive lens group having a positive refractive power, in order from the object side;
the front group positive lens group is composed of a positive lens, a negative lens, and a positive lens, in order from the object side;
the rear group is composed of a positive lens, a negative lens, and a positive lens, in order from the object side; and
when the Abbe number of the most object side positive lens in the front group positive lens group with respect to the d-line is taken as νp, the imaging lens satisfies a conditional expression (1) given below:
νp<30   (1).

2. An imaging lens, consisting of a front group having a positive refractive power, a stop, and a rear group having a positive refractive power, in order from the object side, wherein:
the front group is composed of a front group negative lens group constituted by two or more negative lenses and a front group positive lens group constituted by a plurality of lenses with a positive lens being disposed on the most object side to have a positive refractive power, in order from the object side;
the rear group includes at least one negative lens; and
when the Abbe number of the most object side positive lens in the front group positive lens group with respect to the d-line is taken as νp, and the Abbe number of a negative lens with respect to the d-line, which is the smallest of those of negative lenses included in the rear group with respect to the d-line, is taken as νn, the imaging lens satisfies conditional expressions (1) and (2) given below:
νp<30   (1)

νn<23   (2).

3. The imaging lens of claim 1 , wherein, when the focal length of the entire system is taken as f and the focal length of the front group is taken as fA, the imaging lens satisfies a conditional expression (3) given below:
0.3< f/fA< 1.2   (3).

4. The imaging lens of claim 1 , wherein, when the focal length of the front group is taken as fA and the focal length of the rear group is taken as fB, the imaging lens satisfies a conditional expression (4) given below:
0.1< fA/fB< 1.2   (4).

5. The imaging lens of claim 1 , wherein, when the radii of curvature of the object side surface and the image side surface of the most object side positive lens in the front group positive lens group are taken as Rp1 and Rp2 respectively, the imaging lens satisfies a conditional expression (5) given below:
0.1<( Rp 1− Rp 2)/( Rp 1 +Rp 2)<4.5   (5).

6. The imaging lens of claim 1 , wherein, when the air space between the front group negative lens group and the front group positive lens group on the optical axis is taken as Dnp, and the focal length of the entire system is taken as f, the imaging lens satisfies a conditional expression (6) given below:
0.1 <Dnp/f< 0.8   (6).

7. The imaging lens of claim 2 , wherein the front group positive lens group is composed of a positive lens, a negative lens, and a positive lens, in order from the object side.

8. The imaging lens of claim 2 , wherein:
the front group negative lens group is composed of two negative lenses;
the front group positive lens group is composed of a positive lens, a negative lens, and a positive lens, in order from the object side; and
the rear group is composed of a positive lens, a negative lens, and a positive lens, in order from the object side.

9. The imaging lens of claim 1 , wherein at least one of the most image side lens in the front group negative lens group, the most image side lens in the front group positive lens group, and the most image side lens in the rear group is an aspherical lens.

10. The imaging lens of claim 1 , wherein the imaging lens satisfies a conditional expression (1′) given below:
νp<25   (1′).

11. The imaging lens of claim 1 , wherein the imaging lens satisfies a conditional expression (1″) given below:
νp<23   (1″).

12. The imaging lens of claim 2 , wherein the imaging lens satisfies a conditional expression (2′) given below:
νn<20   (2′).

13. The imaging lens of claim 3 , wherein the imaging lens satisfies a conditional expression (3′) given below:
0.4< f/fA< 1.0   (3′).

14. The imaging lens of claim 4 , wherein the imaging lens satisfies a conditional expression (4′) given below:
0.2< fA/fB< 1.0   (4′).

15. The imaging lens of claim 5 , wherein the imaging lens satisfies a conditional expression (5′) given below:
0.15<( Rp 1 −Rp 2)/( Rp 1+ Rp 2)<4.1   (5′).

16. The imaging lens of claim 6 , wherein the imaging lens satisfies a conditional expression (6′) given below:
0.2< Dnp/f< 0.6   (6′).

17. An imaging apparatus equipped with the imaging lens of claim 1 .

18. An imaging apparatus equipped with the imaging lens of claim 2 .

Assignees

• Fujifilm Corp

Inventors

• Sun Ping

Classifications

• G02B13/04 Primary

  Reversed telephoto objectives · CPC title

• G02B13/18 Primary

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

• H04N5/2254 Primary

  Electricity · mapped topic