| 摘要 |
PURPOSE:To improve a tracking characteristic to provide specified quality of signals and to improve the quality of the resultant reproduced image by changing pregrooves for tracking in such a manner that said grooves are deeper from an inside peripheral side toward an outside peripheral side. CONSTITUTION:An intermediate layer 12 and a recording layer 13 are successively provided to a substrate 11 formed with the pregrooves for tracking on the surface. The pregrooves are so formed that the depth thereof changes to d1, d2...dn-1, dn from the center of a revolving shaft. The depth thereof is so set as to increase continuously from the inside peripheral side toward the outside peripheral side like d1<d2<...<dn-1<dn. The depth of the tracking guide grooves formed after the formation of the layers 12, 13 is thereby made uniform from the inside peripheral side up to the outside peripheral side, by which the high tracking accuracy is obtd. and the uniform quality of the signals is obtd. The image of the resultant reproduced image is thus improved. |
