PURPOSE: To easily manufacture an eccentric Fresnel lens by taking out two parts for forming a sheet having a linear prism group of the same shape from a metallic mold, and forming the eccentric Fresnel lens from two parts, respectively by a compression molding system or an injection molding system.
CONSTITUTION: A concentric Fresnel lens sheet generating metallic mold 21 in which the center of a sheet and the center of a Fresnel lens coincide with each other is manufactured. By cutting out this metallic mold 21, metallic molds 16a, 17a for two pieces of eccentric Fresnel lens sheets are obtained. Also, it is possible to cut out two pairs of eccentric Fresnel lens metallic molds 23a and 23b, and 24a and 24b of the same shape can be cut out of one piece of concentric Fresnel lens sheet metallic mold 22. By a compression molding method for using the metallic molds obtained in such a way and a press machine, or by an injection molding method, the eccentric Fresnel lens sheet is manufactured. In such a way, the manufacture is simplified.
MINOURA NOBUO
KUREMATSU KATSUMI
YANAGI HARUYUKI
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