Patent ID: 7755847

Claim:
A zoom lens system, in order from the object side to the image side, comprising a first lens unit having negative optical power, a second lens unit having positive optical power and a third lens unit having positive optical power, wherein the first lens unit, in order from the object side to the image side, consists of a first lens element that has a concave surface at least on the image side and that has negative optical power and a second lens element that has a convex surface at least on the object side and that has positive optical power, the second lens unit, in order from the object side to the image side, comprises a third lens element being one single lens element, a cemented lens element fabricated by cementing a fourth lens element and a fifth lens element having optical power of mutually different signs, and a sixth lens element being one single lens element, in zooming from a wide-angle limit to a telephoto limit, all of the first lens unit, the second lens unit and the third lens unit move along an optical axis, and the following conditions (1), (I-2) and (5) are satisfied: 5.0<αi W <20.0 (1) n 11 ≧1.9 (I-2) 0.1<( n 11 −1)·( n 12 −1)· d·f W /( r 12 ·r 21 )<0.3 (5) (wherein, 3.2<f T /f W and ω W >35) where, αi W is an incident angle of a principal ray to an image sensor at a maximum image height at a wide-angle limit (defined as positive when the principal ray is incident on a light acceptance surface of the image sensor in a state of departing from the optical axis), n 11 is a refractive index of the first lens element to the d-line, n 12 is a refractive index of the second lens element to the d-line, r 12 is a radius of curvature of the image side surface of the first lens element, r 21 is a radius of curvature of the object side surface of the second lens element, d is an optical axial distance between the image side surface of the first lens element and the object side surface of the second lens element, ω W is a half view angle (°) at a wide-angle limit, f T is a focal length of the entire system at a telephoto limit, and f W is a focal length of the entire system at a wide-angle limit.