主权项 |
1. An imaging lens comprising a first lens element, a second lens element, a third lens element, a fourth lens element and a fifth lens element arranged in order from an object side to an image side along an optical axis of said imaging lens, each of said first lens element, said second lens element, said third lens element, said fourth lens element and said fifth lens element having a refractive power, 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 the optical axis, and a convex portion in a vicinity of a periphery of said second lens element; said image-side surface of said third lens element has a concave portion in a vicinity of the optical axis, and a convex portion in a vicinity of a periphery of said third lens element; said object-side surface of said fifth lens element has a concave portion in a vicinity of a periphery of said fifth lens element; said imaging lens does not include any lens element with a refractive power other than said first lens element, said second lens element, said third lens element, said fourth lens element and said fifth lens element; and said imaging lens satisfies TTL/T5≦9.8 and TTL/T1≦11.00, where TTL represents a distance at the optical axis between said object-side surface of said first lens element and an image plane at the image side, T1 represents a thickness of said first lens element at the optical axis, T5 represents a thickness of said fifth lens element at the optical axis; and said imaging lens further satisfies BFL/Gaa≧1.50, where BFL represents a distance at the optical axis between said image-side surface of said fifth lens element and the image plane at the image side, and Gaa represents a sum of four air gap lengths among said first lens element, said second lens element, said third lens element, said fourth lens element and said fifth lens elements at the optical axis. |