| 摘要 |
A front component of a varifocal camera objective, axially shiftable for focusing purposes, is provided with a lens mount held by an axially extending guide rod which is slidably received in an inner annular flange and an end wall of a lens barrel. The guide rod has a rear extremity provided with male threads engaged by a drive nut held captive in the end wall, the nut being provided with outer gear teeth meshing on the one hand with a pinion, driven by a reversible electric motor via a slipping clutch, and on the other hand with a toothed wheel on the shaft of a milled setting wheel which projects fron the camera housing. An ancillary rod, parallel to the driven guide rod but shorter than the latter, slides only in the annular flange and has its rear end gripped by a bracing ring also engaging the driven guide rod to form a cage.
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