| 摘要 |
A lens holding barrel is fitted in a fixed barrel in a manner that the lens holding barrel is slidable in optical axis direction. A cam ring is rotatably fitted on outer periphery of the fixed lens. Front regulating members are formed on front end of the fixed barrel, and rear regulating member are formed on rear end of the fixed barrel. Three cutouts are formed on inner surface of the cam ring at even intervals, and cams are formed between these cutouts. Vertical walls are formed at both ends of each cam. The cam ring is fitted onto the fixed barrel after the each front regulating member is faced to the each cutout. After that, the cam ring is positioned between the front regulating member and the rear regulating member by rotation of the cam ring. When the cam ring is rotated in a predetermined range, each cam pushes a cam projection against the biasing of the biasing ring, to move the lens holding barrel in the optical axis direction. If the cam ring is rotated beyond the predetermined range, the cam projection contacts the vertical wall to prevent further rotation of the cam ring. The cam ring cannot be rotated to a position where the front regulation member faces the cutout, after fitted on the fixed barrel.
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