GB881942A - Improvements in or relating to optical objectives - Google Patents

Abstract

881,942. Optical objectives. TAYLOR, TAYLOR & HOBSON Ltd. Nov. 26, 1957 ,[Dec. 4, 1956], No. 37032/56. Class 97(1). In an optical objective comprising from front to rear a simple positive lens, two compound meniscus components concave towards a diaphragm therebetween, and two simple positive lenses, the sum of the radii of the facing surfaces of the compound components is between 1.33 and 2.33 times the length of the air space separating them, the 'thickness of the front compound component is between 0.1F and 0.16F and the thickness of the rear compound component is between 0.08F and 0.14F, F being the equivalent focal length of the objective. The compound components are as shown preferably doublets. The radius R 8 is preferably between 0.2F and 0.4F and the lower of this surface lies between 8 and 12 times the reciprocal of the sum of the focal lengths of the two positive lenses at the rear. The difference in refractive index between the two elements of the rear doublet may be less than 0.04 whilst the cemented surface of this doublet is concave to the front and has a radius R 7 between 0.5F and 2F. The index difference in the front doublet is between 0.06 and 0.12 and the radius of the cemented surface R 4 , which is convex to the front, lies between 1.5F and 5F. Optical data are given for one example of the objective shown.