Patent ID: 6560042
Filing Date: 2003-05-06
Classification: G02B

Abstract:
A wide-angle lens system comprising a negative first lens group, and a positive second lens group, in this order from an object,wherein said positive second lens group comprises a positive front sub-lens group and a positive rear sub-lens group, in this order from said object; wherein upon focusing from an infinite object distance to a closer object distance, a first focusing lens group comprising said first lens group and said positive front sub-lens group which are arranged to move integrally, and a second focusing lens group comprising said positive rear sub-lens group are independently moved from the image side toward the object side so that the distance between said first focusing lens group and said second focusing lens group are made shorter; and wherein said wide-angle lens system satisfies the following conditions: 0.5<H1/H2R<0.9 1.7PAV 0.5<Xan/Xbn<1.0 wherein H1 designates the radius of a bundle of axial light rays on the most object-side surface of said first lens group, when said object at an infinite photographing distance is in an in-focus state; H2R designates the radius of a bundle of axial light rays on the most object-side surface of said rear sub-lens group of said second lens group, when said object at an infinite photographing distance is in an in-focus state; nPAV designates the averaged refractive indexes of the d-line with respect to positive lens elements in said second lens group; Xan designates a distance along which said first focusing lens group is advanced, the distance of which is defined by the position of said first focusing lens group corresponding to an infinite photographing distance and the position thereof corresponding to the shortest photographing distance; and Xbn designates a distance along which said second focusing lens group is advanced, the distance of which is defined by the position of said second focusing lens group corresponding to an infinite photographing distance and the position thereof corresponding to the shortest photographing distance.