| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a compact imaging lens which has a brightness of F2.4 or less and has a five-lens configuration.SOLUTION: An imaging lens 10 comprises, in order from the object side, a positive first lens L1, a negative second lens L2 having a concave surface on the image side, a third lens L3, a fourth lens L4, and a fifth lens L5 having a concave surface on the image side, the first lens L1 being the lens with the highest refractive power. An aperture stop S is located on the object side from the third lens L3. All the lenses are made of plastic materials. Both surfaces of the fourth lens L4 have aspherical shapes and have extrema at points P1, P2 respectively, while the aspherical image-side surface S52 of the fifth lens L5 has aspherical shape and has an extremum at a point P3. The imaging lens 10 satisfies the following conditional expressions: -10<ν2-ν3<25...(1), 0.08<D6/f<0.30...(2), whereν3 andν2 represent Abbe numbers of the third lens L3 and second lens L2, respectively, and D6 represents an air gap distance between the third lens L3 and fourth lens L4, while f represents a focal length of the entire system of the imaging lens 10.</p> |
