Imaging lens and imaging apparatus including the imaging lens

Patent metadata

Field	Value
Publication number	US-9778460-B2
Application number	US-201615256760-A
Country	US
Kind code	B2
Filing date	Sep 6, 2016
Priority date	Sep 28, 2015
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

An imaging lens consists of three lenses of, in order from an object side, a first lens having a biconcave shape, and an object-side surface of which is aspherical, a second lens having negative refractive power and a third lens having positive refractive power with a convex surface facing an image side. The absolute value of a curvature radius of an image-side surface of the third lens is less than the absolute value of a curvature radius of an object-side surface of the third lens.

First claim

What is claimed is:

1. An imaging lens consisting of three lenses of, in order from an object side:
a first lens having a biconcave shape, and an object-side surface of which is aspherical;
a second lens having negative refractive power; and
a third lens having positive refractive power with a convex surface facing an image side,
wherein the absolute value of a curvature radius of an image-side surface of the third lens is less than the absolute value of a curvature radius of an object-side surface of the third lens.

2. The imaging lens, as defined in claim 1 , further comprising:
an aperture stop located between the second lens and the third lens.

3. The imaging lens, as defined in claim 2 , wherein the object-side surface of the first lens includes at least one inflection point at a radially inward position toward an optical axis from an intersection of the object-side surface of the first lens and a principal ray at a maximum angle of view.

4. The imaging lens, as defined in claim 1 , wherein the following conditional expression is further satisfied:
−10< L 1 f/L 1 r<− 0.1  (1), where

L1f: a paraxial curvature radius of the object-side surface of the first lens, and
L1r: a paraxial curvature radius of an image-side surface of the first lens.

5. The imaging lens, as defined in claim 1 , wherein the following conditional expression is further satisfied:
−0.9<( L 1 f+L 1 r )/( L 1 f−L 1 r )<0.9  (2), where

L1f: a paraxial curvature radius of the object-side surface of the first lens, and
L1r: a paraxial curvature radius of an image-side surface of the first lens.

6. The imaging lens, as defined in claim 1 , wherein the following conditional expression is further satisfied:
−0.2< f/f 1<−0.05  (3), where

f1: a focal length of the first lens at a wavelength of 850 nm, and
f: a focal length of an entire system at the wavelength of 850 nm.

7. The imaging lens, as defined in claim 1 , wherein the following conditional expression is further satisfied:
0.5< f 1/ f 2<5  (4), where

f1: a focal length of the first lens at a wavelength of 850 nm, and
f2: a focal length of the second lens at the wavelength of 850 nm.

8. The imaging lens, as defined in claim 1 , wherein the second lens has a meniscus shape with a convex surface facing the object side.

9. The imaging lens, as defined in claim 1 , wherein the following conditional expression is further satisfied:
0.1<( L 2 f−L 2 r )/( L 2 f+L 2 r )<1  (5), where

L2f: a paraxial curvature radius of an object-side surface of the second lens, and
L2r: a paraxial curvature radius of an image-side surface of the second lens.

10. The imaging lens, as defined in claim 1 , wherein the following conditional expression is further satisfied:
−3< d 23/ f 12<−1  (6), where

d23: a distance on an optical axis between the second lens and the third lens, and
f12: a combined focal length of the first lens and the second lens at a wavelength of 850 nm.

11. The imaging lens, as defined in claim 4 , wherein the following conditional expression is further satisfied:
−5< L 1 f/L 1 r<− 0.2  (1-1), where

L1f: a paraxial curvature radius of the object-side surface of the first lens, and
L1r: a paraxial curvature radius of an image-side surface of the first lens.

12. The imaging lens, as defined in claim 5 , wherein the following conditional expression is further satisfied:
−0.7<( L 1 f+L 1 r )/( L 1 f−L 1 r )<0.7  (2-1), where

L1f: a paraxial curvature radius of the object-side surface of the first lens, and
L1r: a paraxial curvature radius of an image-side surface of the first lens.

13. The imaging lens, as defined in claim 6 , wherein the following conditional expression is further satisfied:
−0.17< f/f 1<−0.07  (3-1), where

f1: a focal length of the first lens at a wavelength of 850 nm, and
f: a focal length of an entire system at the wavelength of 850 nm.

14. The imaging lens, as defined in claim 7 , wherein the following conditional expression is further satisfied:
0.7< f 1/ f 2<3.5  (4-1), where

f1: a focal length of the first lens at a wavelength of 850 nm, and
f2: a focal length of the second lens at the wavelength of 850 nm.

15. The imaging lens, as defined in claim 9 , wherein the following conditional expression is further satisfied:
0.5<( L 2 f−L 2 r )/( L 2 f+L 2 r )<0.98  (5-1), where

L2f: a paraxial curvature radius of an object-side surface of the second lens, and
L2r: a paraxial curvature radius of an image-side surface of the second lens.

16. The imaging lens, as defined in claim 10 , wherein the following conditional expression is further satisfied:
−2.5< d 23/ f 12<−1.2  (6-1), where

d23: a distance on an optical axis between the second lens and the third lens, and
f12: a combined focal length of the first lens and the second lens at a wavelength of 850 nm.

17. An imaging apparatus comprising:
an imaging lens, as defined in claim 1 .

Assignees

• Fujifilm Corp

Inventors

• Iwasaki Tatsuro
• Cho Michio

Classifications

• G02B27/0081 Primary

  with means for altering, e.g. enlarging, the entrance or exit pupil · CPC title

• G02B9/12 Primary

  having three components only · CPC title

• G06V10/147

  Details of sensors, e.g. sensor lenses (fingerprint or palmprint sensors G06V40/13; vascular sensors G06V40/145; eye sensors G06V40/19) · CPC title

• G06K9/00885

  Physics · mapped topic

• G02B13/002

  having at least one aspherical surface · CPC title