Patent ID: 8908278

Claim:
A composite optical sheet, comprising: a lower sheet and an upper sheet, wherein the upper sheet and the lower sheet each includes a transparent flat plate-shaped body and a plurality of lenses arranged on a surface of the body to form a regular pattern, in which a distance between any one center of a lens and a center of a neighboring lens is more than 1 μm but less than 30 μm, wherein a ratio of a lens diameter of the lower sheet relative to that of the upper sheet is more than 2 but less than 1,000, wherein a concavely curved portion is formed at a discrete space formed between lenses of the plurality of lenses of the lower sheet in a body direction, wherein the concavely curved portion is a circle or an oval tangent to the body of the optical sheet and to the lens, and wherein a diameter of the circle or a length of a major axis and a length of a minor axis is more than 0.1 μm but less than 1,000 μm.