Imaging lens system

Patent metadata

Field	Value
Publication number	US-9316819-B2
Application number	US-201213677556-A
Country	US
Kind code	B2
Filing date	Nov 15, 2012
Priority date	Sep 10, 2012
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

Abstract

This invention provides an imaging lens system, in order from an object side to an image side comprising: a first positive lens element having a convex object-side surface at a paraxial region and a convex image-side surface at the paraxial region; a plastic positive second lens element having a concave object-side surface at the paraxial region, a convex image-side surface at the paraxial region, and both of the object-side and image-side surfaces being aspheric; and a plastic negative third lens element having a concave object-side surface at the paraxial region, a concave at the paraxial region and convex at a peripheral region image-side surface, and both of the object-side and image-side surfaces being aspheric.

First claim

What is claimed is:

1. An imaging lens system, in order from an object side to an image side comprising:
a first lens element with positive refractive power having a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region;
a plastic second lens element with positive refractive power having a concave object-side surface at a paraxial region, a convex image-side surface at a paraxial region, and both of the object-side and image-side surfaces thereof being aspheric; and
a plastic third lens element with negative refractive power having a concave object-side surface at a paraxial region, a concave at a paraxial region and convex at a peripheral region image-side surface, and both of the object-side and image-side surfaces thereof being aspheric;
wherein the lens elements of the imaging lens system with refractive power are only the first lens element, the second lens element, and the third lens element, a curvature radius of the object-side surface of the first lens element is R1, a curvature radius of the image-side surface of the first lens element is R2, a focal length of the first lens element is f1, a focal length of the second lens element is f2, and they satisfy the following relations:
−0.5<( R 1+ R 2)/( R 1− R 2)<1.0; and

1.65< f 1/ f 2<5.0.

2. The imaging lens system according to claim 1 , wherein the imaging lens system further comprises a stop disposed between the first lens element and the second lens element, an axial distance between the stop and an image plane is SL, an axial distance between the object-side surface of the first lens element and the image plane is TTL, and they satisfy the following relation:
0.65< SL/TTL< 0.88.

3. The imaging lens system according to claim 2 , wherein the focal length of the first lens element is f1, the focal length of the second lens element is f2, and they satisfy the following relation:
2.0< f 1/ f 2<3.4.

4. The imaging lens system according to claim 3 , wherein at least one critical point is formed on the object-side surface of the third lens element.

5. The imaging lens system according to claim 3 , wherein a curvature radius of the object-side surface of the third lens element is R5, a focal length of the imaging lens system is f, and they satisfy the following relation:
−1.33< R 5/ f<− 0.55.

6. The imaging lens system according to claim 3 , wherein a central thickness of the second lens element is CT2, a focal length of the imaging lens system is f, and they satisfy the following relation:
0.28< CT 2/ f< 0.50.

7. The imaging lens system according to claim 3 , wherein the imaging lens system is used for optical wavelengths ranging from 780 nm to 950 nm.

8. The imaging lens system according to claim 1 , wherein the curvature radius of the object-side surface of the first lens element is R1, the curvature radius of the image-side surface of the first lens element is R2, and they satisfy the following relation:
−0.1<( R 1+ R 2)/( R 1− R 2)<0.8.

9. The imaging lens system according to claim 8 , wherein a curvature radius of the object-side surface of the third lens element is R5, a curvature radius of the image-side surface of the third lens element is R6, and they satisfy the following relation:
0<( R 5+ R 6)/( R 5− R 6)<0.8.

10. The imaging lens system according to claim 8 , wherein the imaging lens system further comprises a stop, and the stop is closer to the object side than a vertex on the optical axis of the image-side surface of the first lens element.

11. The imaging lens system according to claim 8 , wherein a focal length of the imaging lens system is f, the focal length of the second lens element is f2, and they satisfy the following relation:
2.0< f/f 2<3.6.

12. The imaging lens system according to claim 1 , wherein a distance in parallel with an optical axis from a point on the object-side surface of the third lens element to an axial vertex on the object-side surface of the third lens element is Sag31, a height perpendicular to the optical axis from the point on the object-side surface of the third lens element to the optical axis is Y, a derivative of the distance Sag31 with respect to the height Y is Dsag31, and Dsag31 changes from positive to negative or vice versa at least twice between a paraxial region and a peripheral region of the object-side surface of the third lens element.

13. The imaging lens system according to claim 1 , wherein the object-side surface of the first lens element is concave at a peripheral region.

14. The imaging lens system according to claim 1 , wherein an axial distance between the object-side surface of the first lens element and the image-side surface of the third lens element is Td, and it satisfies the following relation:
1.0 mm< Td< 2.70 mm.

15. An imaging lens system, in order from an object side to an image side comprising:
a first lens element with positive refractive power having a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region;
a plastic second lens element with positive refractive power having a concave object-side surface at a paraxial region, a convex image-side surface at a paraxial region, and both of the object-side and image-side surfaces thereof being aspheric; and
a plastic third lens element with negative refractive power having a concave at a paraxial region and convex at a peripheral region image-side surface, and both of an object-side surface and the image-side surface thereof being aspheric;
wherein the lens elements of the imaging lens system with refractive power are only the first lens element, the second lens element, and the third lens element, the imaging lens system is used for optical wavelengths ranging from 780 nm to 950 nm, a curvature radius of the object-side surface of the first lens element is R1, a curvature radius of the image-side surface of the first lens element is R2, a focal length of the first lens element is f1, a focal length of the second lens element is f2, and they satisfy the following relation:
−0.5<( R 1+ R 2)/( R 1− R 2)<1.0; and

2.0< f 1/ f 2<3.4.

16. The imaging lens system according to claim 15 , wherein an object-side surface of the third lens element is concave at a paraxial region.

17. The imaging lens system according to claim 15 , wherein an axial distance between the object-side surface of the first lens element and the image-side surface of the third lens element is Td, and it satisfies the following relation:
1.0 mm< Td< 2.70 mm.

18. The imaging lens system according to claim 15 , wherein a distance in parallel with an optical axis from a point on the object-side surface of the third lens element to an axial vertex on the object-side surface of the third lens element is Sag31, a height perpendicular to the optical axis from the point on the object-side surface of the third lens element to the optical axis is Y, a derivative of the distance Sag31 with respect to the height Y is Dsag31, and Dsag31 changes from positive to negative or vice versa at least twice between a paraxial region and a peripheral region of the object-side surface of the third lens element.

Assignees

• Largan Precision Co Ltd

Inventors

• Hsu Po-Lun
• Chen Wei-Yu
• Hsueh Chun-Che

Classifications

• G02B13/18 Primary

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

• G02B9/12

  having three components only · CPC title

• G02B13/0035 Primary

  having three lenses · CPC title

• G02B13/14

  for use with infrared or ultraviolet radiation ({G02B13/008, } G02B13/16 take precedence) · CPC title