Lens assembly of optical imaging system
A lens assembly of optical imaging system includes a first lens element, a second lens element, and a third lens element. The first lens element with positive refractive power has a convex object-side surface near an optical axis. The second lens element with negative refractive power has a concave object-side surface near the optical axis, and is made of plastic. The object-side surface and the image-side surface of the second lens element are aspheric. The third lens element with negative refractive power has an image-side surface being concave near the optical axis and convex away from the optical axis, and is made of plastic. The object-side surface and the image-side surface of the third lens element are aspheric.
1. A lens assembly of 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 near an optical axis being convex;
a second lens element with negative refractive power having an object-side surface near the optical axis being concave, which is made of plastic and has both of the object-side surface and an image-side surface being aspheric; and
a third lens element with negative refractive power having an image-side surface being concave near the optical axis and convex away from the optical axis, which is made of plastic and has both of an object-side surface and the image-side surface being aspheric;
the lens assembly of optical imaging system satisfying the following conditions:
0.7<( V 1 −V 2 )/( V 1 −V 3 )<1.5;
30< V 2 +V 3 <65;
0.70< V 3 /V 2 ≦1.10; and
−0.22< f/f 2 <0,
wherein V 1 is an Abbe number of the first lens element, V 2 is an Abbe number of the second lens element, V 3 is an Abbe number of the third lens element, f is a focal length of the lens assembly of optical imaging system, and f 2 is a focal length of the second lens element.
2. The lens assembly of optical imaging system according to claim 1 , wherein the image-side surface of the second lens element is convex near the optical axis and the object-side surface of the third lens element is convex near the optical axis.
3. The lens assembly of optical imaging system according to claim 2 , wherein the lens assembly of optical imaging system satisfies the following condition:
35< V 2 +V 3 <55,
wherein V 2 is the Abbe number of the second lens element, and V 3 is the Abbe number of the third lens element.
4. The lens assembly of optical imaging system according to claim 3 , wherein the first lens element has an image-side surface and the lens assembly of optical imaging system satisfies the following condition:
−1.0< R 1 /R 2 <0.20,
wherein R 1 is a curvature radius of the object-side surface of the first lens element, and R 2 is a curvature radius of the image-side surface of the first lens element.
5. The lens assembly of optical imaging system according to claim 4 , wherein the lens assembly of optical imaging system satisfies the following condition:
0.08< f 2 /f 3 <2.0,
wherein f 2 is the focal length of the second lens element, and f 3 is a focal length of the third lens element.
6. The lens assembly of optical imaging system according to claim 3 , wherein the first lens element has an image-side surface being concave near the optical axis, and the lens assembly of optical imaging system comprises a stop and satisfies the following condition:
0.93< SL/TTL< 1.05,
wherein SL is an axial distance between the stop and an image plane, and TTL is an axial distance between the object-side surface of the first lens element and the image plane.
7. The lens assembly of optical imaging system according to claim 6 , wherein the image-side surface of the first lens element is convex away from the optical axis.
8. The lens assembly of optical imaging system according to claim 7 , wherein the lens assembly of optical imaging system satisfies the following condition:
0.5< T 12 /T 23 <2.0,
wherein T 12 is an axial distance between the first lens element and the second lens element, and T 23 is an axial distance between the second lens element and the third lens element.
9. The lens assembly of optical imaging system according to claim 6 , wherein the lens assembly of optical imaging system satisfies the following condition:
0< R 1 /R 2 <0.10,
wherein R 1 is a curvature radius of the object-side surface of the first lens element, and R 2 is a curvature radius of the image-side surface of the first lens element.
10. The lens assembly of optical imaging system according to claim 3 , wherein the second lens element has an inclination toward the image side at an end part of a peripheral region within an effective radius of the image-side surface of the second lens element.
11. The lens assembly of optical imaging system according to claim 3 , wherein the lens assembly of optical imaging system satisfies the following condition:
40< V 2 +V 3 <49,
wherein V 2 is the Abbe number of the second lens element, and V 3 is the Abbe number of the third lens element.
12. The lens assembly of optical imaging system according to claim 3 , wherein the lens assembly of optical imaging system satisfies the following conditions:
N 1 <N 2 ;
N 1 <N 3 ;
1.60< N 2 ; and
1.60< N 3 ,
wherein N 1 is an index of refraction of the first lens element, N 2 is an index of refraction of the second lens element, and N 3 is an index of refraction of the third lens element.
13. A lens assembly of 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 near an optical axis being convex;
a second lens element with negative refractive power having an object-side surface near the optical axis being concave, which is made of plastic and has the object-side surface and an image-side surface being aspheric; and
a third lens element with negative refractive power having an image-side surface being concave near the optical axis and convex away from the optical axis, which is made of plastic and has an object-side surface and the image-side surface being aspheric, wherein the object-side surface of the third lens element is convex near the optical axis;
the lens assembly of optical imaging system satisfying the following conditions:
0.7<( V 1 −V 2 )/( V 1 −V 3 )<1.5;
30< V 2 +V 3 <65;
−0.45< f/f 2 <0; and
0.70< V 3 /V 2 ≦1.10,
wherein V 1 is an Abbe number of the first lens element, V 2 is an Abbe number of the second lens element, V 3 is an Abbe number of the third lens element, f is a focal length of the lens assembly of optical imaging system, and f 2 is a focal length of the second lens element.
14. The lens assembly of optical imaging system according to claim 13 , wherein the image-side surface of the second lens element is convex near the optical axis.
15. The lens assembly of optical imaging system according to claim 14 , wherein the lens assembly of optical imaging system satisfies the following condition:
35< V 2 +V 3 <55,
wherein V 2 is the Abbe number of the second lens element, and V 3 is the Abbe number of the third lens element.
16. The lens assembly of optical imaging system according to claim 15 , wherein the first lens element has an image-side surface and the lens assembly of optical imaging system satisfies the following condition:
−0.8< R 1 /R 2 <0.2,
wherein R 1 is a curvature radius of the object-side surface of the first lens element, and R 2 is a curvature radius of the image-side surface of the first lens element.
17. The lens assembly of optical imaging system according to claim 16 , wherein the second lens element has an inclination toward the image side at an end part of a peripheral region within an effective radius of the image-side surface of the second lens element.
18. The lens assembly of optical imaging system according to claim 17 , wherein the lens assembly of optical imaging system satisfies the following condition:
40< V 2 +V 3 <49,
wherein V 2 is the Abbe number of the second lens element, and V 3 is the Abbe number of the third lens element.
19. The lens assembly of optical imaging system according to claim 17 , wherein the lens assembly of optical imaging system satisfies the following condition:
−0.30< f/f 2 <0,
wherein f is the focal length of the lens assembly of optical imaging system, and f 2 is the focal length of the second lens element.
20. The lens assembly of optical imaging system according to claim 19 , wherein the lens assembly of optical imaging system satisfies the following condition:
0.5< T 12 /T 23 <2.0,
wherein T 12 is an axial distance between the first lens element and the second lens element, and T 23 is an axial distance between the second lens element and the third lens element.
21. The lens assembly of optical imaging system according to claim 15 , wherein the first lens element has an image-side surface being concave near the optical axis and convex away from the optical axis.
22. The lens assembly of optical imaging system according to claim 21 , wherein the lens assembly of optical imaging system satisfies the following condition:
0.08< f 2 /f 3 <2.0,
wherein f 2 is the focal length of the second lens element, and f 3 is a focal length of the third lens element.
23. The lens assembly of optical imaging system according to claim 15 , wherein the lens assembly of optical imaging system satisfies the following condition:
0.7<( V 1 −V 2 )/( V 1 −V 3 )≦1.25,
wherein V 1 is the Abbe number of the first lens element, V 2 is the Abbe number of the second lens element, and V 3 is the Abbe number of the third lens element.