| 摘要 |
PURPOSE:To obtain a zoom lens of high variable power for finite distance by allowing an optical system which consists of lenses with positive, positive, negative, positive, and positive lens element in five groups successively from a subject side to meet specific requirements. CONSTITUTION:When the optical systems consisting of lens elements in five groups is varied in power from the low power side to the high power side, the 2nd lens group and the 5th lens group are positioned closer to the object side at the high power side than at the low power side, the 3rd lens group moves monotonously to the image plane side, and inequalities I -VIII hold. In the inequalities, fW is the focal length of the whole system on the low power side, f1 is the focal length of the (i)th lens group, and f1+2W is the composite focal length of the 1st and the 2nd lens groups on the low power side; and DELTAX2, DELTAX3, and DELTAX5 are the movement extents of the 2nd, the 3rd, and the 5th lens groups from the low power side to the high power side, and fT is the focal length of the whole system on the high power side. |
