Patent ID: 7791819
Filing Date: 2010-09-07
Classification: G02B

Abstract:
1. A zoom lens system comprises a negative first lens group, a positive second lens group, and a positive third lens group, in this order from an object, wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between said negative first lens group and said positive second lens group decreases, and the distance between said positive second lens group and said positive third lens group increases; wherein said negative first lens group comprises a negative first lens element, a negative second lens element having a weaker negative refractive power, and a positive third lens element, in this order from the object; and wherein said second lens element of said negative first lens group satisfies the following condition: wherein ra designates a radius of curvature of the object-side surface of said second lens element of said negative first lens group; and rb designates a radius of curvature of the image-side surface of said second lens element of said negative first lens group; and wherein said positive second lens group comprises a positive first lens element, a negative second lens element, and a positive or negative third lens element having a weaker refractive power, in this order from the object; and wherein said third lens element of said positive second lens group satisfies the following condition: −0.3<( wherein r3 designates a radius of curvature of the object-side surface of said third lens element of said positive second lens group; and r4 designates a radius of curvature of the image-side surface of said third lens element of said positive second lens group.