Imaging lens system
An imaging lens system includes, arranged in succession from an object side to an image side, an aperture stop S, a first lens L 1 having a positive refractive power, a second lens L 2 having a negative refractive power, a third lens L 3 having a positive refractive power, a fourth lens L 4 having a positive refractive power, and a fifth lens L 5 having a negative refractive power. 0.70≦f 1 /f≦0.85; −1.15≦(R 1 +R 2 )/(R 1 −R 2 )≦−1.00; −0.55≦(R 3 +R 4 )/(R 3 −R 4 )≦−0.20; 0.09≦d 8 /f≦0.15; f/f 1 is respectively a focal length of the lens system LA or lens L 1 ; R 1 /R 2 is respectively a curvature radius of the object/image side of the lens L 1 ; R 3 /R 4 is a curvature radius of the object/image side of the lens L 2 ; d 8 is an axial distance between the image side of the lens L 4 to the object side of the lens L 5.
1. An imaging lens system LA comprising, arranged in succession from an object side to an image side:
a first lens L 1 having a positive refractive power,
a second lens L 2 having a negative refractive power,
a third lens L 3 having a positive refractive power,
a fourth lens L 4 having a positive refractive power,
and a fifth lens L 5 having a negative refractive power,
wherein the following conditions (1)˜(4) are satisfied:
0.70≦ f 1/ f≦ 0.85 (1)
−1.15≦( R 1+ R 2)/( R 1− R 2)≦−1.00 (2)
−0.55≦( R 3+ R 4)/( R 3− R 4)≦−0.22 (3)
0.09≦ d 8/ f≦ 0.15 (4)
where,
f is a focal length of the imaging lens system LA;
f 1 is a focal length of the first lens L 1 ;
R 1 is a curvature radius of the object side of the first lens L 1 ;
R 2 is a curvature radius of the image side of the first lens L 1 .
R 3 is a curvature radius of the object side of the second lens L 2 ;
R 4 is a curvature radius of the image side of the second lens L 2 ;
d 8 is an axial distance between the image side of the fourth lens L 4 to the object side of fifth lens L 5 .
2. The imaging lens system LA as claimed in claim 1 further satisfying the following condition (5):
0.12≦ d 6/ f≦ 0.15 (5)
Where:
f is the focal length of the imaging lens system LA;
d 6 is an axial distance between the image side surface of the third lens L 3 and the object side surface of the fourth lens L 4 .
3. The imaging lens system LA as claimed in claim 1 further satisfying the following condition (6):
−2.50≦ f 2/ f≦− 1.00 (6)
Where:
f is the focal length of the imaging lens system LA;
f 2 is a focal length of the second lens L 2 .
4. The imaging lens system LA as claimed in claim 1 further satisfying the following conditions (7)-(8):
f 3/ f≧ 50.00 (7)
( R 5+ R 6)/( R 5− R 6)≦−8.00 (8)
Where:
f is the focal length of the imaging lens system LA;
f 3 is a focal length of the third lens L 3 ;
R 5 is a curvature radius of the object side the third lens L 3 ;
R 6 is a curvature radius of the image side of the third lens L 3 .