Patent ID: 9541734
Date: 2017-01-10
CPC Classifications: G02B

Claim:
1. An optical imaging lens, sequentially from an object side to an image side along an optical axis, comprising first, second, third, and fourth lens elements, each of said first, second, third, and fourth lens elements having refracting power, an object-side surface facing toward the object side, an image-side surface facing toward the image side, and a central thickness defined along an optical axis, wherein: said first lens element has negative refracting power, said object-side surface of said first lens element comprises a convex portion in a vicinity of a periphery of the-first lens element, said image-side surface of said first lens element comprises a concave portion in a vicinity of the optical axis and a concave portion in a vicinity of a periphery of the-first lens element; said second lens element has positive refracting power, said object-side surface of said second lens element comprises a convex portion in a vicinity of the optical axis and a convex portion in a vicinity of a periphery of the second lens element; said third lens element has negative refracting power, said object-side surface of said third lens element comprises a concave portion in a vicinity of the optical axis and a concave portion in a vicinity of a periphery of the third lens element, said image-side surface of said third lens element comprises a convex portion in a vicinity of the optical axis and a convex portion in a vicinity of a periphery of the third lens element; said fourth lens element has positive refracting power, said object-side surface of said fourth lens element comprises a convex portion in a vicinity of the optical axis, said image-side surface of said fourth lens element comprises a concave portion in a vicinity of the optical axis; a back focal length of the optical imaging lens, which is defined as the distance from the image-side surface of the fourth lens element to an image plane along the optical axis, is represented by BFL, an air gap between the third lens element and the fourth lens element along the optical axis is represented by G34, a central thickness of the third lens element is represented by T3, and T3, BFL and G34 satisfy the equations: BFL/G34≦13.0 and BFL/T3≦5.0; the optical imaging lens comprises no other lenses having refracting power beyond the four lens elements.