Fresnel lens, screen, image displaying device, lens forming mold manufacturing method and lens manufacturing method

摘要

A Fresnel lens has a plurality of pitch areas in which a plurality of hybrid type prism portions are arranged. Each hybrid type prism portion has a refraction type prism portion and a total reflection type prism portion. In the refraction type prism portion, a ray of incident light Li1 of an incident angle “a” is refracted twice and goes out as a ray of outgoing light Lo1 of an outgoing angle “f”. In the total reflection type prism portion, a ray of incident light Li2 of the incident angle “a” is refracted, totally reflected and refracted in that order and goes out as a ray of outgoing light Lo2 parallel to the ray of outgoing light Lo1.