Non-true-circular optical disk

Abstract

A non-true-circular optical disk includes a disk substrate which internally touches a hypothetical true-circle corresponding to an outer periphery of a true-circular optical disk of a certain standard size. The disk substrate has a non-true-circular contour corresponding to a configuration shaped such that at least one cut-out portion is formed at an outer periphery of the hypothetical true-circle to thereby enhance a design. The disk substrate includes at least one inscribed outer peripheral edge internally touching the hypothetical true-circle. The aforementioned at least one inscribed outer peripheral edge includes a plurality of positioning points meeting a geometrical positional relationship by which a rotational center of the disk substrate coincides with a center of the hypothetical true-circle and a movement of the rotational center relative to the center of the hypothetical true-circle is prevented in a state that the at least one inscribed outer peripheral edge internally touches the hypothetical true-circle.

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