PURPOSE: To electrify only a required area corresponding to a set magnification by providing plural long holes different in length on the outside peripheral part of a charging charger and turning the charging charger in accordance with movement of a lens unit of variable power conversion.

CONSTITUTION: Long holes 10a, 10b... different in length are provided on the outside peripheral part of a conductive pipe 9, and a gear 9a is provided in the end part of the pipe 9. The gear 9a is turned by an interlocking mechanism consiting of a lever 17, a slide pin 19, a supporting shaft 16, a hole part 15a of a lever 15, and a pin 18 provided on a lens holding base 3a. When a lens 3 is slid along a lens base rail 3b in the direction of an arrow B, the lever 17 is slid in the direction of an arrow F by the interlocking mechanism, and the gear 9a is turned in the direction of an arrow G to switch long holes 10a, 10b.... Thus, only the part corresponding to the width of the set magnetificaton corresponding to the position of the lens 3 is electrified with the simple structue to reduce the cost.