Patent ID: 8409686

Claim:
An optical recording medium comprising: three or more information recording layers; a plurality of intermediate layer disposed between adjacent information recording layers and having a refractive index; a cover layer disposed between a light incident surface and an information recording layer being the closest from the light incident surface and having a refractive index, wherein the refractive index of the plurality of intermediate layers is greater than the refractive index of the cover layer; a verified thickness H k at a reference refractive index n is defined by the equation H k =T k ×[tan {arcsin(NA/n k )}/tan {arcsin(NA/n)}], where n k is a refractive index of an intermediate layer being the k th farthest from a light incident surface, T k is a physical thickness of that intermediate layer, H k can realize the same optical path length as that of the k th intermediate layer, and NA is a numerical aperture of an optical system for the optical recording medium; a verified thickness H c at a reference refractive index n is defined by the equation H c =T c ×[tan {arcsin(NA/n c )}/tan {arcsin(NA/n)}], where n c is a refractive index of the cover layer, T c is a physical thickness of that cover layer, H c can realize the same optical path length as that of the cover layer, and NA is a numerical aperture of an optical system for the optical recording medium; and the verified thickness of H c of the cover layer is larger than the total verified thickness ΣH k of all intermediate layers.