The present invention is an imaging lens in which various aberrations are satisfactorily corrected, the optical length is short, and a sufficient back focus is secured. The imaging lens is constituted by arranging a first lens L 1 , an aperture diaphragm S 1 , a second lens L 2 , and a third lens L 3 in succession from the object side to the image side.
1. An imaging lens comprising a first lens L 1 , an aperture diaphragm S 1 , a second lens L 2 , and a third lens L 3 , and constituted such that said first lens L 1 , said aperture diaphragm S 1 , said second lens L 2 , and said third lens L 3 are arranged in succession from the object side to the image side,
wherein said first lens L 1 is a resin lens having a positive refractive power and a meniscus shape in which the convex surface faces the object side,
said second lens L 2 is a resin lens having a positive refractive power and a meniscus shape in which the convex surface faces the image side, and
said third lens L 3 is a resin lens having a negative refractive power,
both surfaces of said first lens L 1 being aspherical, both surfaces of said second lens L 2 being aspherical, and at least one surface of said third lens L 3 being aspherical, and
said imaging lens satisfying the following conditions,
0.40 <r 1 /r 2 <0.65 (1)
0.08 <D 2 /f <0.1 (2)
0.2 <D 3 /f <0.3 (3)
1.0 <d/f <1.5 (4)
0.4 <b f /f <0.6 (5)
where
f is the focal length of the entire lens system,
r 1 is the radius of curvature of the object-side surface of the first lens L 1 in the vicinity of the optical axis,
r 2 is the radius of curvature of the image-side surface of the first lens L 1 in the vicinity of the optical axis,
D 2 is the interval between the first lens L 1 and second lens L 2 ,
D 3 is the thickness at the center of the second lens L 2 ,
d is the distance from the object-side surface of the first lens L 1 to the imaging surface, and
b f is the distance from the image-side surface of the third lens to the imaging surface.
2. The imaging lens according to claim 1 , wherein said first lens L 1 , said second lens L 2 , and said third lens L 3 are formed from a material having an Abbe number within a range of thirty to sixty.
3. The imaging lens according to claim 1 , wherein said first lens L 1 , said second lens L 2 , and said third lens L 3 are formed using a cycloolefin plastic as a material.