Imaging lens

Patent metadata

Field	Value
Publication number	US-10209485-B2
Application number	US-201615389267-A
Country	US
Kind code	B2
Filing date	Dec 22, 2016
Priority date	Dec 25, 2015
Publication date	Feb 19, 2019
Grant date	Feb 19, 2019

Abstract

There is provided an imaging lens which is low-profile, has a small f-value, and obtains wide field of view which aberrations are properly corrected, in order from an object side to an image side, comprising a first lens having positive refractive power and a convex surface on an object side near an optical axis, a second lens having negative refractive power and a concave surface on the object side near the optical axis, a third lens having positive refractive power and a convex surface on the image side as a double-sided aspheric lens and a fourth lens having negative refractive power and a concave surface on an image side near the optical axis as a double-sided aspheric lens, wherein a conditional expression (1) below is satisfied:

8.5< ih/f <1.0  (1)
where f denotes the focal length of the overall optical system, and ih denotes maximum image height.

First claim

What is claimed is:

1. An imaging lens, in order from an object side to an image side, comprising:
a first lens having a meniscus shape with positive refractive power and a convex surface on the object side near an optical axis;
a second lens having negative refractive power and a concave surface on the object side near the optical axis;
a third lens having positive refractive power and a convex surface on the image side as a double-sided aspheric lens; and
a fourth lens having a meniscus shape with negative refractive power and a concave surface on the image side near the optical axis as a double-sided aspheric lens, wherein:
conditional expressions (1), (7), (10), (11a), and (13) below are satisfied:
0.85< ih/f< 1.0  (1)

0.14< |r 1 /r 2|<0.7  (7)

−0.9< f 4/ f<− 0.6  (10)

−1.5< r 5/ f<− 0.6  (11a)

9.0<( T 1/ f )*100<16.0  (13)

where f denotes a focal length of an overall optical system, ih denotes maximum image height, r1 denotes a curvature radius near the optical axis on an object-side surface of the first lens, r2 denotes a curvature radius near the optical axis on an image-side surface of the first lens, f4 denotes a focal length of the fourth lens, r5 denotes a curvature radius near the optical axis of an object-side surface of the third lens, and T1 denotes a distance on the optical axis from the image-side surface of the first lens to an object-side surface of the second lens.

2. The imaging lens according to claim 1 , wherein a conditional expression (2) below is satisfied:
Fno≤ 2.4  (2)

where Fno denotes a F-number.

3. The imaging lens according to claim 2 , wherein a conditional expression (3) below is satisfied:
0.1< |r 3/ r 4|<0.6  (3)

where r3 denotes a curvature radius near an optical axis of the object-side surface of the second lens, and r4 denotes a curvature radius near the optical axis of an image-side surface of the second lens.

4. The imaging lens according to claim 3 , wherein a conditional expression (4) below is satisfied:
1.2<( r 7+ r 8)/( r 7 −r 8)<2.5  (4)

where r7 denotes a curvature radius near an optical axis of an object-side surface of the fourth lens, and r8 denotes a curvature radius near the optical axis of an image-side surface of the fourth lens.

5. The imaging lens according to claim 4 , wherein a conditional expression (5) below is satisfied:
0.15<|Sag4/ D 2|<0.4  (5)

where Sag4 denotes an amount of Sag at a maximum effective diameter on the image-side surface of the second lens, and D2 denotes a thickness on the optical axis of the second lens.

6. The imaging lens according to claim 4 , wherein a conditional expression (6) below is satisfied:
0.02<|Sag5/ D 3|<0.13  (6)

where Sag5 denotes an amount of Sag at maximum effective diameter on the object-side surface of the third lens, and D3 denotes a thickness on the optical axis of the third lens.

7. The imaging lens according to claim 3 , wherein a conditional expression (8) below is satisfied:
−7.5< f 2/ f<− 2.0  (8)

where f2 denotes a focal length of the second lens.

8. The imaging lens according to claim 2 , wherein a conditional expression (9) below is satisfied:
0.3< f 3/ f< 1.2  (9)

where f3 denotes a focal length of the third lens.

9. The imaging lens according to claim 2 , wherein a refractive power of the third lens is most strong among a refractive power of the first lens, the second lens, the third lens, and the fourth lens.

10. The imaging lens according to claim 2 , wherein a conditional expression (12) below is satisfied:
0.035< T 3/ D 3<0.2  (12)

where T3 denotes a distance on the optical axis from an image-side surface of the third lens to an object-side surface of the fourth lens, and D3 denotes a thickness on the optical axis of the third lens.

11. The imaging lens according to claim 1 , wherein a conditional expression (14) below is satisfied:
0.55<TTL/2 ih< 0.85  (14)

where TTL is a total track length.

Assignees

• Kantatsu Co Ltd

Inventors

• Yuza Shingo
• Kamada Kenichi

Classifications

• G02B13/004 Primary

  having four lenses · CPC title

• G02B13/18

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

• G02B13/22

  Telecentric objectives or lens systems · CPC title

• G02B9/34

  having four components only · CPC title

• G02B13/06

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