Lens tube for variable focal-length lens - contains cam ring in threaded engagement with inner thread of stationary tube, with linear movement guide rotatable relatively to cam ring

摘要

The linear movement guide is movable in common with the cam ring in the direction of the optical axis. At least three movable lens groups are guided in the direction of the optical axis with the linear movement guide. A first lens assembly (18) for the first object-side lens group (L1) is in threaded engagement with a further thread (13c) of the cam ring. Several cam tracks (13d,13e) are provided on the cam ring for drive of the lens groups (L3) following the first (L1). The first lens assembly (18) has an outer thread and the cam ring has an inner thread (13c). A guide arrangement is provided on the linear movement guide (14) for determining a position in which the inner thread of the cam ring comes into engagement in a peripheral direction with the outer thread of the first lens assembly. USE/ADVANTAGE - A lens tube which can be assembled easily by having a simple construction.