SINGLE FOCUS LENS FOR ELECTRONIC STILL CAMERA

摘要

PROBLEM TO BE SOLVED: To provide a single focus lens for an electronic still camera which exhibits good color reproducibility with a simple configuration and reduces ghost phenomenon by giving an infrared cut coat to a meniscus lens on the object side from a diaphragm so as to make a curvature with which the shape of its surface becomes almost vertical to the principal ray of an incident light at all viewing angles. SOLUTION: A coat surface 3 where the infrared cut coat is applied at the lens surface of a meniscus lens located on the object side from the diaphragm is made into a shape having the curvature almost vertical to the incident light at all viewing angles. More specifically, when a normal to an arbitrary point on the coat surface 3 is set to be N, it is preferable to set the shape of the coat surface 3 and the entire optical system so that the principal ray P of incident luminous flux has a deviation angleΔθa smaller than 6 deg. to the normal N at all viewing angles (Fig. (a)) and marginal light beams M in central luminous flux among incident luminous flux have a deviation angleΔθb smaller than 7 deg. to the surface normal N (Fig. (b)).