Optical imaging system, image capturing unit and electronic device

Patent metadata

Field	Value
Publication number	US-9341815-B1
Application number	US-201514625043-A
Country	US
Kind code	B1
Filing date	Feb 18, 2015
Priority date	Jan 7, 2015
Publication date	May 17, 2016
Grant date	May 17, 2016

Abstract

An optical imaging system includes, in order from an object side to an image side, a first lens element, a second lens element and a third lens element. The first lens element with positive refractive power has an object-side surface being convex and an image-side surface being convex in a paraxial region. The second lens element with positive refractive power has an object-side surface being concave and an image-side surface being convex in a paraxial region. The third lens element with negative refractive power has an image-side surface being concave in a paraxial region thereof, wherein the image-side surface of the third lens element has at least one convex shape in an off-axis region thereof. The optical imaging system further comprises a stop between the image-side surface of the first lens element and the object-side surface of the second lens element. The lens elements are made of plastic material.

First claim

What is claimed is:

1. An optical imaging system comprising, in order from an object side to an image side:
a first lens element with positive refractive power having an object-side surface being convex in a paraxial region thereof and an image-side surface being convex in a paraxial region thereof, wherein both of the object-side surface and the image-side surface of the first lens element are aspheric, and the first lens element is made of plastic material;
a second lens element with positive refractive power having an object-side surface being concave in a paraxial region thereof and an image-side surface being convex in a paraxial region thereof, wherein both of the object-side surface and the image-side surface of the second lens element are aspheric, and the second lens element is made of plastic material; and
a third lens element with negative refractive power having an image-side surface being concave in a paraxial region thereof, wherein the image-side surface of the third lens element has at least one convex shape in an off-axis region thereof, both of an object-side surface and the image-side surface of the third lens element are aspheric, and the third lens element is made of plastic material;
wherein the optical imaging system has a total of three lens elements with refractive power which are the first lens element, the second lens element and the third lens element, the optical imaging system further comprises a stop located between the image-side surface of the first lens element and the object-side surface of the second lens element;
wherein a focal length of the first lens element is f 1 , a focal length of the second lens element is f 2 , a focal length of the third lens element is f 3 , a central thickness of the first lens element is CT 1 , a central thickness of the third lens element is CT 3 , an axial distance between the stop and the image-side surface of the third lens element is SD, 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 the following conditions are satisfied:
| f 3|< f 2< f 1;
1.55<CT1/CT3; and
0.55< SD/TD< 0.80.

2. The optical imaging system of claim 1 , wherein an axial distance between the first lens element and the second lens element is T 12 , an axial distance between the second lens element and the third lens element is T 23 , and the following condition is satisfied:
2.5< T 12/ T 23.

3. The optical imaging system of claim 2 , wherein the central thickness of the first lens element is CT 1 , the central thickness of the third lens element is CT 3 , and the following condition is satisfied:
1.80<CT1/CT3<4.50.

4. The optical imaging system of claim 2 , wherein a sum of central thicknesses of the first lens element, the second lens element and the third lens element is ΣCT, the central thickness of the first lens element is CT 1 , and the following condition is satisfied:
1.40<ΣCT/CT1<2.60.

5. The optical imaging system of claim 1 , wherein the central thickness of the first lens element is CT 1 , the central thickness of the third lens element is CT 3 , and the following condition is satisfied:
2.40<CT1/CT3<3.50.

6. The optical imaging system of claim 1 , wherein the third lens element has an object-side surface being concave in a paraxial region thereof.

7. The optical imaging system of claim 1 , wherein an Abbe number of the second lens element is V 2 , an Abbe number of the third lens element is V 3 , and the following condition is satisfied:
0.80< V 2/ V 3<1.33.

8. The optical imaging system of claim 1 , wherein the 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 the following condition is satisfied:
TD< 2.25 millimeters (mm).

9. The optical imaging system of claim 1 , wherein an Abbe number of the second lens element is V 2 , an Abbe number of the third lens element is V 3 , and the following condition is satisfied:
V 2+ V 3<70.

10. The optical imaging system of claim 1 , wherein a refractive index of the second lens element is N 2 , a refractive index of the third lens element is N 3 , and the following condition is satisfied:
3.00< N 2+ N 3<3.40.

11. The optical imaging system of claim 1 , wherein an axial distance between the object-side surface of the first lens element and an image surface is TL, an entrance pupil diameter of the optical imaging system is EPD, and the following condition is satisfied:
1.0< TL /EPD<3.4.

12. The optical imaging system of claim 1 , wherein the focal length of the first lens element is f 1 , the focal length of the second lens element is f 2 , the focal length of the third lens element is f 3 , and the following condition is satisfied:
1.25<(| f 3|/ f 2)+( f 2/ f 1)<1.85.

13. The optical imaging system of claim 12 , wherein the focal length of the first lens element is f 1 , a curvature radius of the image-side surface of the first lens element is R 2 , and the following condition is satisfied:
−1.5< f 1/ R 2<0.

14. The optical imaging system of claim 1 , wherein the optical imaging system is for being operated within a wavelength range of 750 nanometers (nm) to 1050 nm.

15. The optical imaging system of claim 1 , further comprising a filter, wherein at least one of the first lens element, the second lens element, the third lens element and the filter is made of visible-light-absorbing material.

16. An image capturing unit, comprising:
the optical imaging system of claim 1 ; and
an image sensor, wherein the image sensor is disposed on the image side of the optical imaging system.

17. An electronic device comprising:
the image capturing unit of claim 16 .

18. An optical imaging system comprising, in order from an object side to an image side:
a first lens element with positive refractive power having an object-side surface being convex in a paraxial region thereof and an image-side surface being convex in a paraxial region thereof, wherein both of the object-side surface and the image-side surface of the first lens element are aspheric, and the first lens element is made of plastic material;
a second lens element with positive refractive power having an object-side surface being concave in a paraxial region thereof and an image-side surface being convex in a paraxial region thereof, wherein both of the object-side surface and the image-side surface of the second lens element are aspheric, and the second lens element is made of plastic material; and
a third lens element with negative refractive power having an image-side surface being concave in a paraxial region thereof, wherein the image-side surface of the third lens element has at least one convex shape in an off-axis region thereof, both of an object-side surface and the image-side surface of the third lens element are aspheric, and the third lens element is made of plastic material;
wherein the optical imaging system has a total of three lens elements with refractive power which are the first lens element, the second lens element and the third lens element, the optical imaging system further comprises a filter, and at least one of the first lens element, the second lens element, the third lens element and the filter is made of visible-light-absorbing material;
wherein a focal length of the first lens element is f 1 , a focal length of the second lens element is f 2 , a focal length of the third lens element is f 3 , a central thickness of the first lens element is CT 1 , a c

Assignees

• Largan Precision Co Ltd

Inventors

• Hsueh Chun-Che
• Chen Chun-Yen
• Chen Wei-Yu

Classifications

• H04N23/54

  Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils · CPC title

• G02B9/12

  having three components only · CPC title

• G02B13/0035 Primary

  having three lenses · CPC title

• G02B13/008

  designed for infrared light · CPC title

• G02B5/208

  for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation · CPC title