| 摘要 |
PURPOSE:To shorten the closest object distance without increasing overall length by making the object distance of the case when the focusing lens group is extended most <=25 times the focal length in a zoom lens system of which the focusing lens group is the rear group of the zoom system. CONSTITUTION:In a zoom system of which a focusing lens group 3 is the rear group of a zoom system (1-3) and focusing is accomplished by driving of the whole or part thereof, the lens group 1 is 5.5mm. ahead of a conventional system when telephoto side T. The lens group 3 is also retreated 8.2mm. on shifting to the telephto side T from the position at the end of the wide side W by zoom operation in an infinite subject distance. At this time, the rate D of extension of the lens group is 18.2mm. and the rate of extension on the wide side is 10mm. with respect to a subject distance 1.5m. D is <=25 times the focal length. Thereby, the closest object distance is shortened without increasing the overall length. |
