| 摘要 |
PURPOSE:To enable the high resolution lens to be manufactured inexpensively from a minimum number of lenses by so constituting the lens that it consists of two lens systems having aspherical face on the second face. CONSTITUTION:Refractive indices of two lenses 1 and 2 are let to be n1, n2 respectively and the focal length of the lens 1 is let to be f1. The first face thereof is made a convex face of a strong radius r1 of curvature and the second face a convex or concave aspherical lens. The front of the lens 2 is made a spherical face of a strong radius r3 of curvature and the back face a gentle convex or concave aspherical lens. Further the air spacing between the lenses 1 and 2 is let to be d2 and the combined focal length of the lenses to be f. With such constitution, condition formulas I thru IV are satisfied, whereby the second face is so constituted as to be the aspherical face whose vertex is approximated by a spherical face and which includes at least up to the terms proportional to the fourth power of incident height. |
