| 摘要 |
PURPOSE:To make it possible to set a rear focus conversion lens to even an objective lens having a short back focus and to make the conversion lens compact by constituting the conversion lens with a positive front group and a negative rear group and moving both groups to focus the lens and satisfying prescribed conditions. CONSTITUTION:A lens system RFC (focal length fR) set between an objective lens L0 and a camera body consists of a positive front group (f1) G1 and a negative rear group (f2) G2, and both groups are moved to focus the lens system. The front group has a negative meniscus lens, whose convex is directed to the object side, and a positive lens following this lens. In equalities (1)-(6) are satisfied when a magnifying power of the focal length in the in-focus state in the infinity, a variation in the focus range of a composite back focus Bf, and a length from the lens surface nearest to the object of the RFC to the image point due to the object lens are denoted as beta, DELTABf, and d0 respectively. |
