| 摘要 |
PURPOSE:To obtain a recording reproducing signal and a track address signal with high quality by forming a guide track with prescribed depth and width to a base of an optical memory element to improve the shape of the guide track and the shape of a track address pit. CONSTITUTION:A tracking servo (TS) signal is at maximum with d=lambda/8n and a track address signal (TN) is at maximum with d=lambda/4n, where (h) is the width of a guide track or a track address of an optical memory element, (d) is the depth of them, lambda is the operating light wavelength and (n) is a refractive index at the guide track forming part. In order to improve the S/N of an information signal, the (h) is deeper than the lambda/8n. The noise at lambda/48n<=d<=lambda/12n is nearly 0.03-0.5 time the case with lambda/8n and the quality of the TN and TS signals. The TS signal is maximum with h=0.5.lambda/NA (NA is the numerical aperture of an objective lens), but in order to reduce the noise, the relation of 0.5.lambda/NA<=h <=0.7.lambda/NA is selected. |
