| 摘要 |
PURPOSE:To eliminate the influence of the meander of a substrate which protects a recording film and to make focusing and tracking highly precisely by coating on the substrate protecting a recoding film a substance whose reflective index is larger than that of the substrate. CONSTITUTION:A laser light 4, passing through a glass substrate 2, is reflected by a recording layer 1 and returned to an optical head. The reflective index of the substrate 2 without a coating material 3 is assumed as n1 and the meander of the surface as l1, and when a substance 3 of the reflective index of n2 is coated on the surface, the meander of the surface is reduced to (d). The reflective index of the substance 3 is selected so that the optical distances of the raised part and the lower part of the surface winding be equal. Thus, the variance in optical distance caused by the meander of the substrate is reduced with the thin coating without raised in precision of the substrate surface. |
