Imaging lens
A compact, small F-value imaging lens with a wide field of view which corrects aberrations properly. Its elements are arranged in order from an object side to an image side: an aperture stop, a positive first lens having convex surfaces on the object and image sides, a negative second lens having a concave image-side surface, a meniscus positive third lens having a convex image-side surface, and a negative double-sided aspheric fourth lens having a concave image-side surface. With an F-value smaller than 2.4, it satisfies conditional expressions (1) to (3): 0.8< ih/f <0.95 (1) TLA /2 ih <0.9 (2) −4.0< r 3/ r 4<6.0 (3) where ih: maximum image height f: focal length of the imaging lens overall optical system TLA: total track length r3: curvature radius of the second lens object-side surface r4: curvature radius of the second lens image-side surface.
1. An imaging lens in which elements are arranged in order from an object side to an image side, comprising:
an aperture stop;
a first lens with positive refractive power having a convex surface on the object side and the image side;
a second lens with negative refractive power having a concave surface on the image side;
a third lens with positive refractive power as a meniscus lens having a convex surface on the image side; and
a fourth lens with negative refractive power as a double-sided aspheric lens having a concave surface on the image side,
wherein an F-value is smaller than 2.4; and
conditional expressions (1) (2 b ), and (3) below are satisfied:
0.8< ih/f< 0.95 (1)
TLA/ 2 ih< 0.78 (2 b )
−4.0< r 3/ r 4<6.0 (3)
where
ih: maximum image height
f: focal length of an overall optical system of the imaging lens
TLA: distance on an optical axis from an object-side surface of an optical element located nearest to an object to an image plane without a filter or the like
r 3 : curvature radius of the object-side surface of the second lens
r 4 : curvature radius of the image-side surface of the second lens.
2. The imaging lens according to claim 1 ,
wherein a conditional expression (4) below is satisfied:
1.1< f 1/ f 3<1.6 (4)
where
f 1 : focal length of the first lens
f 3 : focal length of the third lens.
3. The imaging lens according to claim 1 ,
wherein a conditional expression (5) below is satisfied:
2.0< f 2/ f 4<4.0 (5)
where
f 2 : focal length of the second lens
f 4 : focal length of the fourth lens.
4. The imaging lens according to claim 1 ,
wherein a conditional expression (6) below is satisfied:
−4.5< r 3/ f< 5.5 (6)
where
r 3 : curvature radius of the object-side surface of the second lens
f: focal length of an overall optical system of the imaging lens.
5. The imaging lens according to claim 1 ,
wherein a conditional expression (7) below is satisfied:
2.8< r 5/ r 6<5.0 (7)
where
r 5 : curvature radius of the object-side surface of the third lens
r 6 : curvature radius of the image-side surface of the third lens.
6. The imaging lens according to claim 1 ,
wherein a conditional expression (8) below is satisfied:
−0.05< f 12/ f 34<0.80 (8)
where
f 12 : composite focal length of the first lens and the second lens
f 34 : composite focal length of the third lens and the fourth lens.