| 摘要 |
PROBLEM TO BE SOLVED: To enable accurate automatic focusing even when a moving cam for focusing which enables manual focusing is used by satisfying a specific conditional expression at least at a telephoto end. SOLUTION: At least at the telephoto end, 1.00<γXR/γXO, 10.00<ΔxTR/ΔxWR <15.00, and -0.50<aF/aZ<-0.30 are satisfied. In the inequalities,γXO andγXR are the ratios dBf/dx of the fine movement quantity dBf of an image formation plane to the fine movement quantity dx of a focusing lens group along the optical axis at an infinite-distance focusing point and a short-distance focusing point. ThenΔxWR andΔxTR are the movement quantities of the focusing lens group along the optical axis which are required for focusing from an infinite distance to a short distance at the wide-angle end and telephoto end respectively. Further, aZ and aF are the rotational quantity of the moving cam for focusing corresponding to power variation from the wide-angle end to the telephoto end and the rotational quantity corresponding to power variation from an infinite-distance focusing state to a short-distance focusing state.
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