| 摘要 |
A lens tube for a high vari-focal ratio zoom lens is arranged to individually effect movement of a plurality of lens groups for the purpose of zooming, and to integrally move a plurality of lens groups of the purpose of focusing, and arranged so that a double helicoid mechanism for driving the first lens group is provided on a member constituting the lens tube, the lens tube being arranged so that operation of a zooming mechanism serves to move a focusing mechanism, for the purpose of compensation, by means of the helicoid mechanism mentioned above, and a cam mechanism provided on other members constituting the lens tube.
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