| 摘要 |
PURPOSE:To stabilize a servo circuit and to increase the amplitude of an HF signal by setting the depth of a pre-groove (guide groove) at 20-30nm in order to increase the reflection factor. CONSTITUTION:A postscript type optical disk 2 is produced by forming the thin film 12 of tellurium, aluminum, etc., on the surface of a transparent disk substrate 10 with the thickness of several 10nm. Then the disk 12 is used in a single plate style. The pre-grooves 16' are formed with 20-30nm depth and the film 12 on these pre-grooves 16' is burnt out by the laser light. Thus pits 18 are obtained. Thus the depth of the pre-groove is reduced and therefore the reflection factor, the detecting sensitivity set by a 3-beam method after recording and the focus gains are increased. Thus the load of a servo circuit is reduced and at the same time the level of an HF signal is increased together with the improved S/N. |
