Imaging lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-9645364-B2
Application number	US-201615070690-A
Country	US
Kind code	B2
Filing date	Mar 15, 2016
Priority date	Mar 31, 2015
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

An imaging lens consists of, in order from the object side, a front group having a negative refractive power, a stop, and a rear group having a positive refractive power. The front group consist of a front-group negative lens group that consists of three negative lenses and has a negative refractive power, and a front-group positive lens group that includes one positive lens and one negative lens and has a positive refractive power, where the negative lens is disposed at the most image-side position. The rear group includes two positive lenses and two negative lenses. The imaging lens satisfies condition expression (1): 0.95<−fAn/f<2, where fAn is a focal length of the front-group negative lens group, and f is a focal length of the entire system.

First claim

What is claimed is:

1. An imaging lens consisting of, in order from the object side, a front group having a negative refractive power, a stop, and a rear group having a positive refractive power,
wherein the front group consists of, in order from the object side, a front-group negative lens group having a negative refractive power and a front-group positive lens group having a positive refractive power,
the front-group negative lens group consists of three negative lenses,
the front-group positive lens group includes one positive lens and one negative lens that is disposed at the most image-side position of the front-group positive lens group,
the rear group includes two positive lenses and two negative lenses, and
the condition expression (1) below is satisfied:
0.95<− fAn/f< 2   (1),

where fAn is a focal length of the front-group negative lens group, and f is a focal length of the entire system.

2. The imaging lens as claimed in claim 1 , wherein the condition expression (2) below is satisfied:
0.7<− fA/fB< 10   (2),

where fA is a focal length of the front group, and fB is a focal length of the rear group.

3. The imaging lens as claimed in claim 2 , wherein the condition expression (2-1) below is satisfied:
0.75<− fA/fB< 9   (2-1).

4. The imaging lens as claimed in claim 1 , wherein the condition expression (3) below is satisfied:
0.3< f/fB< 0.6   (3),

where fB is a focal length of the rear group.

5. The imaging lens as claimed in claim 4 , wherein the condition expression (3-1) below is satisfied:
0.305< f/fB< 0.5   (3-1).

6. The imaging lens as claimed in claim 1 , wherein the condition expressions (4) and (5) below are satisfied:
55<νd3<96 (4), and
0.003<ΔθgF3<0.05   (5),

where νd3 is an Abbe number with respect to the d-line of the most image-side negative lens of the front-group negative lens group, and ΔθgF3 is an anomalous dispersion property of the most image-side negative lens of the front-group negative lens group.

7. The imaging lens as claimed in claim 6 , wherein the condition expression (4-1) below is satisfied:
60<νd3<70   (4-1).

8. The imaging lens as claimed in claim 6 , wherein the condition expression (5-1) below is satisfied:
0.004<ΔθgF3<0.006   (5-1).

9. The imaging lens as claimed in claim 1 , wherein each of the first and the second lenses from the object side of the front-group negative lens group is a negative meniscus lens with the convex surface toward the object side.

10. The imaging lens as claimed in claim 1 , wherein the rear group includes a cemented lens formed by, in order from the object side, a negative lens and a biconvex positive lens that are cemented together.

11. The imaging lens as claimed in claim 1 , wherein the rear group includes at least one cemented lens, wherein the most object-side cemented lens of the at least one cemented lens included in the rear group is formed by, in order from the object side, a positive lens and a negative lens that are cemented together, and has the cemented surface that is a convex surface toward the image side.

12. The imaging lens as claimed in claim 1 , wherein the condition expression (1-1) below is satisfied:
1<− fAn/f< 1.5   (1-1).

13. An imaging apparatus comprises the imaging lens as claimed in claim 1 .

Assignees

• Fujifilm Corp

Inventors

• Okada Kazuyoshi
• Sun Ping

Classifications

• G02B13/06 Primary

  Panoramic objectives; So-called "sky lenses" {including panoramic objectives having reflecting surfaces} · CPC title

• G02B13/0045 Primary

  having five or more lenses · CPC title

• G02B13/006

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