| 摘要 |
An imaging lens includes four lenses arranged in order from the object side to the image side: an aperture stop, positive (refractive power) first lens having a convex object-side surface near the optical axis, second lens having a positive meniscus shape near the axis, positive third lens having a convex image-side surface near the axis, and negative fourth lens having a concave image-side surface near the axis. All lens surfaces are aspheric. The image-side aspheric surface of the fourth lens has a pole-change point off the optical axis and conditional expressions (1) and (2) are satisfied: 0.75<TLA/(2IH)<0.90  (1) 0.90<TLA/f<1.30  (2) where TLA: distance on the optical axis from the first lens's object-side surface to the image sensor's image plane without a filter between the fourth lens and image sensor IH: maximum image height f: overall optical system focal length. |
