| 摘要 |
PURPOSE:To obtain a compact lens system, by moving the front group and the rear group so as to satisfy prescribed conditions when focusing a finite object distance, in a focusing lens system which consists of the front group and the rear group having positive and negative refractive power, respectively. CONSTITUTION:A focusing lens system is divided into the front group having positive refractive power, so as to satisfy inequalities I, II. In this state, when focusing a finite object distance, the front group and the rear group are moved in order to satisfy the inequality III. In this regard, fF, fp, DELTA, Xp and Xn in these inequalitiesI-III denote a focal distance of the whole lens system, a focal distance of the whole lens system, a focal distance of the front group, a space between the front and rear groups in the finite object, the quantity of feed of the front group, and the quantity of feed of the rear group, respectively. |
