GB881944A - Improvements in or relating to optical objectives - Google Patents

Abstract

881,944. Optical objectives. TAYLOR, TAYLOR & HOBSON Ltd. June 19, 1958 [Aug. 16, 1957], No. 25927/57. Class 97(1). A 5-component objective comprises a simple collective front component, two simple collective rear components, and two meniscus doublet components, having all their surfaces (including the internal contact surfaces) concave towards the diaphragm in the air space between them, the numerical sum of the radii of the two surfaces bounding said air space lying between 1.33 and 2.0 times the axial length of such air space, whilst the radii of curvature of the internal contact surfaces in the front and rear doublet meniscus components respectively lie between F and 4.33 F; and between F and 10.0 F, where F is the equivalent focal length, the power of the rear surface of the rear doublet meniscus component lying between 5 and 10 times the reciprocal of the sum of the equivalent focal lengths of the two simple collective rear components the mean refractive indices of the material of the rear element of the front meniscus doublet component being less than that of the front element of such component by between 0.05 and 0.13, and also being less than the arithmetic mean of the mean refractive indices of the materials of the front' elements of the two meniscus doublet components, whilst the mean refractive indices of' the materials of the two elements of the rear doublet meniscus component differ from one another by less than 0.04. Optical data are given for four examples of the objective illustrated. Specifications 881,942 and 881,943 are referred to.