| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a zoom lens capable of favorably compensating a distance fluctuation in a field curvature across a wide projection range from close to infinity, and having a favorable optical performance. <P>SOLUTION: The zoom lens includes: a first lens unit disposed closest to an enlargement side and comprising first A and first B lens sub units; and a variable power lens unit disposed at a reduction side with respect to the first lens unit. During focusing, the first A lens sub unit is immobile, and the first B lens sub unit moves towards the reduction side for focusing from the infinity side towards the close side. The zoom lens satisfies the following conditions: -2000<f<SB POS="POST">1B</SB>/f<SB POS="POST">1</SB><-1.0-30<SF<-0.2, where f<SB POS="POST">1B</SB>is a focal length of the first B lens sub unit, and f<SB POS="POST">1</SB>is a focal length of the entire first lens unit. When curvature radii of the lens surface closest to the reduction side and the lens surface closest to the enlargement side of the first B lens sub unit are defined as RR and RF respectively, SF=(RR+RF)/(RR-RF). <P>COPYRIGHT: (C)2013,JPO&INPIT |
