| 摘要 |
PURPOSE:To obtain a lens system of large wide angle zoom ratios and good various aberrations by moving the lens system in such a manner that the spacing between an objective lens group and an intermediate lens group decreases on the long focus side and that the spacing between the intermediate lens group and an eyepiece lens group increases on the long focus side. CONSTITUTION:Specifications of the lens are set as by the equations in order to change the focal length of the entire system while maintaining an image plane position constant. Namely, the lens system consists of an objective lens group L1 having negative refracting power, an intermediate lens group L2 having positive refracting power and an eyepiece lens group L3 having negative refracting power, and the spacing between the lens group L1, L2 on the short focus side decreases on the long focus side, and the spacing between the lens groups L2, L3 on the short focus side increases on the long focus side. The relations of the lens groups L1, L2 are formed by the conditions of an ordinary two component zoom, and the relations of the lens groups L2, L3 are formed by the conditions constituting a telephoto type. Hence, the correction of aberrations and miniaturization are accomplished by the symmetry and degrees of freedom of power disposition by the eyepiece lens group L3, and the lens system of small Petzval sum is obtained. |
