JPS5778013A - Telephoto lens - Google Patents

Abstract

PURPOSE:To obtain highly efficient long focus lenses which are small in size and whose various aberration have been compensated, by a constitution that the power, refractive index, etc., of the diverging rear lens group which forms a telephoto lens together with the converging front lens group, satisfy prescribed conditions. CONSTITUTION:This small-sized telephoto lens is constituted of a converging front lens groupIand a diverging rear lens group II which consists of a positive lens D9 whose convexed side faces to the image side, a cemented negative lens composed of three pairs of a negative and a positive lenses D10 and D11, D14 and D15, D17 and D18, each of which has a convexed diverging cemented surface, and air lenses D12, D14, etc. When the composite power phiR of the rear lens group II, the composite power phiA of the lens D10 and the negative cemented lens, the power phi1 of the lens D10, the power phi2 of the cemented negative lens, the refractive index n1 of the lens D10, and the refractive indexes n2, n3, etc. of the negative and positive lenses of the cemented negative lens are selected to satisfy conditions of expressionsI-V, the curvature of field, spherical aberration, comatic aberration, chromatic aberration, etc., are excellently compensated, and thus, this telephoto lens becomes a small- sized, highly efficient, and long focus telephoto lens.