| 摘要 |
PURPOSE: To provide a zoom lens system capable of carrying out precise autofocusing and manual focusing, by setting a ratio between a power variation turning degree from a wind angle side to a telescopic side and a focusing turning degree from the indefinite distance side to the near distance side so that the sensitivity of a focusing lens group with respect to displacement of an image forming point satisfies a specific condition. CONSTITUTION: A conditioning expression: 1.0<γx R/γx O<-0.7 is satisfied on at least the telescopic side, and the ratio between a turning degree aZ of a focusing moving cam corresponding to a power change from the wide angle side to the telescopic side and a turning degree a, thereof from the indefinite focusing condition to the near distance focusing condition satisfies a conditioning expression: -1.0<aF/aZ<0.7, and accordingly, a conditioning expression 0.3<γa R/γa O<0.7 is satisfied at least on the wide angle end side and on the telescopic end side, whereγx O andγa O, andγx R andγa R are a ratio between an X-axial microdisplacement of a focusing lens group and a microdisplacement of an image forming plane, and a ratio between an angular microdisplacement of the focusing moving cam g2 F and a microdisplacement of the image forming plane at an indefinite focal point and at a near distance focal point, respectively.
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