JPS6425113A - Finite system large aperture single lens - Google Patents

Abstract

PURPOSE:To compensate the spherical aberration, sine condition, astigmatism, and comatic aberration of a single lens greatly and excellently over a wide visual field by forming both convex surfaces of the single lens aspherically, and employing a term of high order of the height from the optical axis up to specific power as their aspherical surface coefficients. CONSTITUTION:A biconvex lens form a reduced image of a body at an infinite distance and an equation I holds for the distance (x) of a point on the aspherical surface from the contact plane at the lens surface peak point, the height (h) from the optical axis, the curvature C of the aspherical surface peak point, the constant (k) of ellipticity, and the coefficient A2i of the aspherical surfaces. Namely, the coefficient of the aspherical surfaces contains the term of high order of the height (h) from the optical axis up to 18th power, and consequently excellent aberrations are obtained. An inequality II shows the range of the refracting power of the object-side surface of the single lens, an inequality III shows a flat image plane having no astigmatism, and an inequality IV shows a range where a decrease in performance due to the parallel eccentricity of the both lens surfaces can be precluded under said conditions, where (f) is the focal length of the single lens surface, r1 the radius of peak curvature of the object-side lens surface, (d) the center thickness of the single lens, and (n) the refractive index of the material of the single lens.