| 摘要 |
PURPOSE:To obtain a good autotracking control signal by specifying the thickness of a medium and the relation between the refractive index and extinction coefft. of the medium. CONSTITUTION:The medium is formed to have the thickness at which the reflectivity is maximized in a region except tracking tracks and the thickness larger than the thickness at which the reflectivity is maximized within the tracking tracks. In addition, the medium is so formed that the refractive index (n) and extinction coefft. K of the medium satisfy the relation K<=0.47n+0.28. A wide range of materials are usable without particularly limiting the same as the medium to be used, if said materials have light reflecting and absorbing properties. The good autotracking control signal of a high contrast ratio is thereby obtd. |
