Patent ID: 7948684

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 comprises at least two lens elements, the second lens unit, in order from the object side to the image side, comprises a first cemented lens element fabricated by cementing two lens elements having optical power of mutually different signs and a second cemented lens element fabricated by cementing two lens elements having optical power of mutually different signs, 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 (6) are satisfied: 5.0<αi W <20.0 (1) n 11 ≧1.9 (I-2) 0.0001<( n 11 −1)·( n 12 −1)· d 2 ·f W /( r 12 ·r 21 ·f T )<0.04 (6) (here, 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 a most object side lens element in the first lens unit to the d-line, n 12 is a refractive index of a most image side lens element in the first lens unit to the d-line r 12 is a radius of curvature of the image side surface of a most object side lens element in the first lens unit, r 12 is a radius of curvature of the object side surface of a most image side lens element in the first lens unit, d is an optical axial distance between the image side surface of a most object side lens element in the first lens unit and the object side surface of a most image lens element in the first lens unit, 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.