Imaging lens and imaging apparatus equipped with the imaging lens

Patent metadata

Field	Value
Publication number	US-9709778-B2
Application number	US-201514864260-A
Country	US
Kind code	B2
Filing date	Sep 24, 2015
Priority date	Mar 27, 2013
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

An imaging lens is constituted by, in order from the object side to the image side: a negative front group; a stop; and a positive rear group. The front group is constituted by, in order from the object side to the image side, a front group negative lens group, constituted by at least two negative lenses, and a front group positive lens group including one negative lens and one positive lens, in which a positive lens is provided most toward the object side. The rear group includes one negative lens and one positive lens. Conditional Formula (1) below is satisfied:

Nan +0.01·ν an <2.15  (1)
wherein Nan and νan respectively are the refractive index with respect to the d line and the Abbe's number with respect to the d line of the negative lens provided most toward the image side within the front group positive lens group.

First claim

What is claimed is:

1. An imaging lens consisting of, in order from the object side to the image side:
a front group having a negative refractive power;
a stop; and
a rear group having a positive refractive power;
the front group consisting of, in order from the object side to the image side, a front group negative lens group having a negative refractive power, constituted by two negative lenses, and a front group positive lens group having a positive refractive power, including one positive lens and one negative lens, in which a positive lens is provided most toward the object side;
the rear group consisting of, in order from the object side to the image side, a positive lens, a first cemented lens formed by cementing a positive lens and a negative lens together, and a second cemented lens formed by cementing a positive lens and a negative lens together; and
Conditional Formula (1) below being satisfied:
Nan +(0.01×ν an )<2.15  (1)

wherein Nan is the refractive index of the negative lens provided most toward the image side within the front group positive lens group with respect to the d line, and νan is the Abbe's number of the negative lens provided most toward the image side within the front group positive lens group with respect to the d line.

2. The imaging lens as defined in claim 1 , in which Conditional Formula (2) below is satisfied:
−1.0 <faN/f<− 0.5  (2)

wherein faN is the focal length of the front group negative lens group, and f is the focal length of the entire lens system.

3. The imaging lens as defined in claim 2 , in which Conditional Formula (2′) below is satisfied:
−0.9 <faN/f<− 0.6  (2′).

4. The imaging lens as defined in claim 1 , in which Conditional Formula (3) below is satisfied:
0.05< Dab/f< 1.55  (3)

wherein Dab is the air distance along the optical axis between the front group and the rear group, and f is the focal length of the entire lens system.

5. The imaging lens as defined in claim 4 , in which Conditional Formula (3′) below is satisfied:
0.10< Dab/f< 1.00  (3′).

6. The imaging lens as defined in claim 5 , in which Conditional Formula (3″) below is satisfied:
0.10< Dab/f< 0.55  (3″).

7. The imaging lens as defined in claim 1 , in which Conditional Formula (4) below is satisfied:
ν bp> 55  (4)

wherein νbp is the Abbe's number of the positive lens most toward the object side in the rear group with respect to the d line.

8. The imaging lens as defined in claim 7 , in which Conditional Formula (4′) is satisfied:
Nbp> 60  (4′).

9. The imaging lens as defined in claim 1 , wherein
the front group negative lens group consists of two negative meniscus lenses having convex surfaces toward the object side.

10. The imaging lens as defined in claim 1 , in which Conditional Formula (1′) below is satisfied:
Nan +(0.01×ν an )<2.05  (1′).

11. An imaging apparatus comprising the imaging lens as defined in claim 1 .

Assignees

• Fujifilm Corp

Inventors

• Sun Ping

Classifications

• G02B15/177

  having a negative front lens or group of lenses · CPC title

• G02B27/0025

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

• G02B5/005

  Diaphragms (for cameras G03B9/02) · CPC title

• G02B13/04 Primary

  Reversed telephoto objectives · CPC title

• G02B9/64

  having more than six components · CPC title