Imaging lens, camera, and portable information terminal device

Patent metadata

Field	Value
Publication number	US-10948683-B2
Application number	US-201816142230-A
Country	US
Kind code	B2
Filing date	Sep 26, 2018
Priority date	Nov 22, 2017
Publication date	Mar 16, 2021
Grant date	Mar 16, 2021

Abstract

An imaging lens includes a front lens group, an aperture stop, and a rear lens group arranged in that order from an object side to an image side. An object-side lens closest to an object within the front lens group and an image-side lens closest to an image within the rear lens group are configured to form only three air lenses therebetween. The air lens is an air gap between an image-side surface of an object-side lens and an object-side surface of an image-side lens. The object-side lens and the image-side lens is adjacent to each other in an optical axis of the imaging lens. The three air lenses include an object-side air lens, an image-side air lens, and an intermediate air lens. The object-side air lens and the image-side air lens is biconvex, and the intermediate air lens is biconcave.

First claim

What is claimed is:

1. An imaging lens, comprising:
a front lens group having positive refractive power;
an aperture stop; and
a rear lens group having positive refractive power,
wherein the front lens group, the aperture stop, and the rear lens group are being arranged in that order from an object side to an image side,
wherein an object-side lens closest to an object within the front lens group and an image-side lens closest to an image within the rear lens group are configured so as to form only three air lenses therebetween, each air lens being an air gap between an image-side surface of an object-side lens and an object-side surface of an image-side lens, the object-side lens and the image-side lens being adjacent to each other in an optical axis of the imaging lens, and
wherein the three air lenses include an object-side air lens disposed closest to the object, an image-side air lens disposed closest to the image, and an intermediate air lens disposed between the object-side air lens and the image-side air lens, the object-side air lens and the image-side air lens being biconvex, and the intermediate air lens being biconcave.

2. The imaging lens according to claim 1 ,
wherein the front lens group includes the object-side air lens,
the rear lens group includes the image-side air lens,
the intermediate air lens is formed between the front lens group and the rear lens group, and
the aperture stop is disposed within the intermediate air lens.

3. The imaging lens according to claim 2 , herein the object-side lens closest to the object in the front lens group has negative refractive power.

4. The imaging lens according to claim 3 ,
wherein the front lens group includes:
a first negative lens disposed closest to the object, the first negative lens having a concave surface facing the image side; and
a second negative lens next to the first negative lens, on the image side relative to the first negative lens, the second negative lens having a concave surface facing the object side,

wherein the object-side air lens is formed between the first negative lens and the second negative lens,
wherein the rear lens group includes:
a meniscus lens disposed closest to the image side, the meniscus lens having a concave surface facing the object side; and
a third negative lens being disposed next to the meniscus lens, on the object side relative to the meniscus lens, the third negative lens having a concave surface facing the object side,

wherein the image-side air lens is formed between the meniscus lens and the third negative lens,
wherein the meniscus lens is one of a single lens and a meniscus cemented lens having a concave surface facing the object side, and
wherein conditional expression [10] below is satisfied:
−0.4< fFF/fRR< 0.6  [10]

where fFF denotes a focal length of the first negative lens, and II denotes a focal length of the meniscus lens.

5. The imaging lens according to claim 1 ,
wherein the front lens group includes three or four lenses, and
the rear lens group includes three or four lenses.

6. The imaging lens according to claim 1 ,
wherein conditional expressions [1] and [2] below are satisfied:
−0.6<( r 1 o+r 2 o )/( r 1 o−r 2 o )<0.2  [1]

−0.6<( r 1 i+r 2 i )/( r 1 i−r 2 i )<0.2  [2]

where
r1o denotes a radius of curvature of the object-side surface of the object-side air lens,
r2o denotes a radius of curvature of the image-side surface of the object-side air lens,
r1i denotes a radius of curvature of the object-side surface of the image-side air lens, and
r2i denotes a radius of curvature of the image-side surface of the image-side air lens.

7. The imaging lens according to claim 1 , wherein conditional expression [3] below is satisfied:
0.0<( r 1 m+r 2 m )/( r 1 m−r 2 m )<1.0  [3]

where
r1m denotes a radius of curvature of the object-side surface of the intermediate air lens, and
r2m denotes a radius of curvature of the image-side surface of the intermediate air lens.

8. The imaging lens according to claim 1 , wherein conditional expression [4] below is satisfied:
0.8< fF/fR< 3.0  [4]

where
fF denotes a focal length of the front lens group, and
fR denotes a focal length of the rear lens group.

9. The imaging lens according to claim 1 , wherein conditional expressions [5] and [6] below are satisfied:
0.7< Y′/f< 0.95  [5]

0.6<tan(θ P max)<0.95  [6]

where
Y′ denotes a maximum image height,
f denotes a focal length of the imaging lens as a whole when the imaging lens is focused on an object at infinity, and
θPmax denotes an angle at which a chief ray reaching the maximum image height hits an image plane.

10. The imaging lens according to claim 1 , wherein conditional expression [7] below is satisfied:
1.3< L/f< 1.9  [7]

where
L denotes a distance between an image plane and a surface closest to the object in the imaging lens when the imaging lens is focused on an object at infinity, and
f denotes a focal length of the imaging lens as a whole when the imaging lens is focused on the object at infinity.

11. The imaging lens according to claim 1 , wherein conditional expression [8] below is satisfied:
0.6< DT/f< 1.1  [8]

where
DT denotes a distance between a surface closest to the object and a surface closest to the image, and
f denotes a focal length of the imaging lens as a whole when the imaging lens is focused on an object at infinity.

12. The imaging lens according to claim 1 , wherein conditional expression [9] below is satisfied:
−4.0< f 1/ f<− 2.2  [9]

where
f1 denotes a focal length of a lens closest to the object in the front lens group, the lens having negative refractive power, and
f denotes a focal length of the imaging lens as a whole when the imaging lens is focused on an object at infinity.

13. A camera mounted with the imaging lens according to claim 1 that serves as an imaging optical system.

14. A portable information terminal device comprising a camera device mounted with the imaging lens according to claim 1 that serves an imaging optical system.

15. The imaging lens of claim 1 , wherein, for each air lens, the air gap occurs, in a direction of an optical axis of the imaging lens, between at least one point on the image-side surface of the object-side lens and a corresponding point on the object-side surface of the image-side lens.

Assignees

• Ohashi Kazuyasu
• Ricoh Co Ltd

Inventors

• Ohashi Kazuyasu

Classifications

• H04N23/55

  Optical parts specially adapted for electronic image sensors; Mounting thereof · CPC title

• G02B9/58 Primary

  arranged - + + - · CPC title

• G02B27/0037

  with diffracting elements (G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876) · CPC title

• G02B7/04

  with mechanism for focusing or varying magnification · CPC title

• G02B7/021 Primary

  for more than one lens · CPC title