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 pluralityof hybrid type prism portions are arranged. Each hybrid type prismportion has a refraction type prism portion and a total reflectiontype prism portion. In the refraction type prism portion, a ray ofincident light Li1 of an incident angle "a" is refracted twice andgoes out as a ray of outgoing light Lo1 of an outgoing angle "f". Inthe total reflection type prism portion, a ray of incident light Li2of the incident angle "a" is refracted, totally reflected and refractedin that order and goes out as a ray of outgoing light Lo2 parallelto the ray of outgoing light Lo1.