Patent ID: 7619834
Filing Date: 2009-11-17
Classification: G02B

Abstract:
1. A zoom lens system comprising: a first lens unit having a negative refractive power; at least one lens unit having a positive refractive power; and an optical element composed of a material that satisfies the following condition: where θ N =(Ng N −NF N )/(NF N −NC N ) and ν N is the Abbe number of the material, and Ng N , NF N , and NC N are the refractive indices of the material for the g-line, F-line, and the C-line, respectively, wherein the first lens unit, an aperture stop, and the at least one lens unit are arranged in this order from an object side to an image side, wherein the zoom lens system performs zooming while changing the distance between the first and the at least one lens unit, and wherein the zoom lens system satisfies the following conditions: where f N is the focal length of the optical element, Lt is the distance from the aperture stop to the optical element in a telephoto end state, Tt is the overall length of the zoom lens system in the telephoto end state, fw is the focal length in a wide-angle end state, and ft is the focal length in the telephoto end state.