Patent ID: 7927520

Claim:
A method of manufacturing an optical sheet that includes a transparent base, a plurality of light focusing elements that are formed on a first surface of the base, a photosensitive resin layer that is formed on a second surface of the base which opposes the first surface, and a plurality of openings that are formed in the photosensitive resin layer, the method comprising: forming the photosensitive resin layer on the second surface; placing a photomask that has a light shielding pattern over at least one of the plurality of light focusing elements; applying parallel light at a first angle with respect to a normal of the base through the photomask and focusing the light using the at least one of the plurality of light focusing elements; applying parallel light at a second angle with respect to the normal of the base through the photomask and focusing the light using the at least one of the plurality of light focusing elements, the second angle being different from the first angle; forming the plurality of openings in the photosensitive resin layer at the positions where the parallel light at the first and second angles is focused on the resin layer by the at least one of the plurality of light focusing elements, wherein focus areas formed by the at least one of the plurality of light focusing elements at the positions in the photosensitive resin layer are deviated from a central axis of the light shielding pattern to a longitudinal direction of the light shielding pattern.