Imaging lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-9739976-B2
Application number	US-201514948861-A
Country	US
Kind code	B2
Filing date	Nov 23, 2015
Priority date	Nov 25, 2014
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

An imaging lens includes, in order from the object side: a positive first lens group; a stop; a positive second lens group; and a negative third lens group. The first lens group includes, in order from the object side, at least one positive single lens, at least one cemented lens, at least one negative single lens, and a negative meniscus single lens. The second lens group includes, in order from the object side, a cemented lens and a biconvex lens. The third lens group includes, in order from the object side, a negative meniscus lens, at least one negative lens, and at least one positive lens. Focusing from infinity to a close distance is performed by moving the first lens group, the stop, and the second lens group while the third lens group is fixed with respect to an imaging surface.

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 positive refractive power; and
a third lens group having a negative refractive power;
the first lens group consisting of, in order from the object side to the image side, one or more positive single lenses, one or more cemented lenses, one or more negative single lenses, and a negative meniscus single lens having a concave surface toward the image side;
the second lens group consisting of, in order from the object side to the image side, a cemented lens formed by cementing a negative lens and a biconvex lens, provided in this order from the object side to the image side, together, and a biconvex lens;
the third lens group consisting of, in order from the object side to the image side, a negative meniscus lens having a concave surface toward the image side, one or more negative lenses, and one or more positive lenses; and
focusing operations to change focus from an object at infinity to an object at a close distance being performed by moving the first lens group, the stop, and the second lens group toward the object side while the third lens group is fixed with respect to an imaging surface.

2. An imaging lens as defined in claim 1 , in which Conditional Formula (1) below is satisfied:
0<− f/f 3<0.28  (1)

wherein f is the focal length of the entire lens system, and f3 is the focal length of the third lens group.

3. An imaging lens as defined in claim 1 , in which Conditional Formula (2) is satisfied:
0<− f 12/ f 3<0.225  (2)

wherein f12 is the combined focal length of the first lens group and a second lens group when focused on an object at infinity, and f3 is the focal length of the third lens group.

4. An imaging lens as defined in claim 1 , in which Conditional Formula (3) below is satisfied:
0<( R 2 f−R 2 r )/( R 2 f+R 2 r )<0.15  (3)

wherein R2f is the radius of curvature of the surface toward the object side of the negative meniscus single lens within the first lens group, and R2r is the radius of curvature of the surface toward the image side of the negative meniscus single lens within the first lens group.

5. An imaging lens as defined in claim 1 , in which Conditional Formula (4) below is satisfied:
0.18< L 2/ R 2 f< 1.0  (4)

wherein L2 is the central thickness of the negative meniscus single lens within the first lens group, and R2f is the radius of curvature of the surface toward the object side of the negative meniscus single lens within the first lens group.

6. An imaging lens as defined in claim 1 , wherein:
a positive lens positioned most toward the image side within the second lens group is designated as a second positive lens; and
Conditional Formula (5) below is satisfied:
0.1<( R 1 r−R 1 f )/( R 1 r+R 1 f )<4.0  (5)

wherein R1r is the radius of curvature of the surface toward the image side of a negative single lens adjacent to the negative meniscus single lens within the first lens group at the object side thereof, and R1f is the radius of curvature of the surface toward the object side of the negative single lens adjacent to the negative meniscus single lens within the first lens group at the object side thereof.

7. An imaging lens as defined in claim 1 , wherein:
a cemented lens formed by cementing a negative lens having a concave surface toward the image side and a positive lens, provided in this order from the object side to the image side, together is provided adjacent to a single negative lens within the first lens group at the object side thereof.

8. An imaging lens as defined in claim 1 , in which Conditional Formula (6) below is satisfied:
0.1<( R 3 r−R 3 f )/( R 3 r+R 3 f )<1.65  (6)

wherein R3r is the radius of curvature of the surface toward the image side of a positive lens provided most toward the image side within the third lens group, and R3f is the radius of curvature of the surface toward the object side of the positive lens provided most toward the image side within the third lens group.

9. An imaging lens as defined in claim 1 , wherein:
the second lens group consists of, in order from the object side to the image side, a cemented lens formed by cementing a biconcave lens and the biconvex lens, provided in this order from the object side to the image side, together, and the biconvex lens.

10. An imaging lens as defined in claim 1 , wherein:
the first lens group, the stop, and the second lens group move integrally during focusing operations.

11. An imaging lens as defined in claim 1 , wherein:
the first lens group and the second lens group move toward the object side such that the distance therebetween becomes greater when changing focus from an object at infinity to an object at a close distance.

12. An imaging lens as defined in claim 1 , in which Conditional Formula (1-1) below is satisfied:
0.01<− f/f 3<0.26  (1-1)

wherein f is the focal length of the entire lens system, and f3 is the focal length of the third lens group.

13. An imaging lens as defined in claim 1 , in which Conditional Formula (2-1) below is satisfied:
0.005<− f 12/ f 3<0.22  (2-1)

wherein f12 is the combined focal length of the first lens group and a second lens group when focused on an object at infinity, and f3 is the focal length of the third lens group.

14. An imaging lens as defined in claim 1 , in which Conditional Formula (3-1) below is satisfied:
0.05<( R 2 f−R 2 r )/( R 2 f+R 2 r )<0.14  (3-1)

wherein R2f is the radius of curvature of the surface toward the object side of the negative meniscus single lens within the first lens group, and R2r is the radius of curvature of the surface toward the image side of the negative meniscus single lens within the first lens group.

15. An imaging lens as defined in claim 1 , in which Conditional Formula (4-1) below is satisfied:
0.2< L 2/ R 2 f< 0.6  (4-1)

wherein L2 is the central thickness of the negative meniscus single lens within the first lens group, and R2f is the radius of curvature of the surface toward the object side of the negative meniscus single lens within the first lens group.

16. An imaging lens as defined in claim 1 , in which Conditional Formula (5-1) below is satisfied:
0.5<( R 1 r−R 1 f )/( R 1 r+R 1 f )<3.0  (5-1)

wherein R1r is the radius of curvature of the surface toward the image side of a negative single lens adjacent to the negative meniscus single lens within the first lens group at the object side thereof, and R1f is the radius of curvature of the surface toward the object side of the negative single lens adjacent to the negative meniscus single lens within the first lens group at the object side thereof.

17. An imaging lens as defined in claim 1 , in which Conditional Formula (6-1) below is satisfied:
0.2<( R 3 r−R 3 f )/( R 3 r+R 3 f )<1.6  (6-1)

wherein R3r is the radius of curvature of the surface toward the image side of a positive lens provided most toward the image side within the third lens group, and R3f is the radius of curvature of the surface toward the object side of the positive lens provided most toward the image side within the third lens group.

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

Assignees

• Fujifilm Corp

Inventors

• Sun Ping

Classifications

• G02B13/02

  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

• G02B9/64 Primary

  having more than six components · CPC title