| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens system which can make precision focusing while reducing backlash influences as much as possible. SOLUTION: The zoom lens system of this invention consists of a main frame, a first and second cams provided free to turn in the direction of the center axis X of the main frame, a first and second drivers to turn the first and second cams respectively around the center axis X, and a lens frame. Since the first and second drivers determine different drive forces and speed reduction rates for the first and second cams having spiral angles different from each other to drive them independently for focusing at different speeds, this zoom lens system can make high-precision focusing by reducing backlashes and maintaining the focusing precision at the same time. COPYRIGHT: (C)2006,JPO&NCIPI
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