| 主权项 |
1. An imaging lens comprising an aperture stop, first, second, third, fourth and fifth lens elements arranged from an object side to an image side in the given order, each of said first, second, third, fourth and fifth lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side, wherein:
said first lens element has a positive refractive power; said image-side surface of said second lens element has a concave portion in a vicinity of a periphery of said second lens element; said object-side surface of said third lens element has a concave portion in a vicinity of a periphery of said third lens element; said object-side surface of said fourth lens element has a convex portion in a vicinity of an optical axis of said imaging lens, and said image-side surface of said fourth lens element has a concave portion in a vicinity of the optical axis; and said fifth lens element is made of a plastic material, and said image-side surface thereof has a concave portion in a vicinity of the optical axis; wherein said imaging lens does not include any lens element with refractive power other than said first, second, third, fourth and fifth lens elements; where said imaging lens satisfies EFL/AC23≧5.70, ALT/CT1≦3.75 and ALT/(CT4+CT5)≧2.90, where EFL represents an effective focal length of said imaging lens, where AC23 represents a distance between said image-side surface of said second lens element and said object-side surface of said third lens element at the optical axis, where ALT represents a sum of a distance between said object-side surface and said image-side surface of said first lens element at the optical axis, the distance between said object-side surface and said image-side surface of said second lens element at the optical axis, the distance between said object-side surface and said image-side surface of said third lens element at the optical axis, a distance between said object-side surface and said image-side surface of said fourth lens element at the optical axis, and a distance between said object-side surface and said image-side surface of said fifth lens element at the optical axis, where CT1 represents the distance between said object-side surface and said image-side surface of said first lens element at the optical axis, where CT4 represents the distance between said object-side surface and said image-side surface of said fourth lens element at the optical axis, and where CT5 represents the distance between said object-side surface and said image-side surface of said fifth lens element at the optical axis. |
