Patent ID: 7639434

Claim:
A compound imaging lens comprising: a first lens, a second lens, and a third lens disposed sequentially in this order, the first lens disposed toward an object, and the third lens disposed toward an image surface; wherein the first lens has a meniscus shape, a positive refraction, and a convex surface, the convex surface facing the object; the second lens has a meniscus shape, a positive refraction, and a concave surface, the concave surface facing the object; the third lens has a convex-type shape facing the object, and a concave-type aspherical shape facing the image surface, the concave-type aspherical shape configured to provide a negative refraction in a radially central portion and a positive refraction in a radially peripheral portion; and three conditions: 0.5H<T0<0.7H (1) 2<φ r 4/φ<2.5 (2) and 0.15<φ r 5/φ<0.3 (3) are satisfied, where H is defined as an effective radius of the surface of the third lens facing the image surface, T0 is defined as a distance between a point on a normal line and an optical axis, the normal line being parallel to the optical axis and normal to the surface of the third lens facing the image surface, φ is defined as a combined refractive power of the first lens, the second lens, and the third lens, φr4 is defined as a refractive power of a surface of the second lens facing the image surface, and φr5 is defined as a refractive power of the surface of the third lens facing the object.