| 摘要 |
PURPOSE:To make the recording density high and uniform as the whole while holding the S/N of a reproduced signal in a prescribed value or more, by dividing the recording face of a disc to plural regions in the direction of radius and making the width of recording tracks narrower in regions on the outside circumferential side and making that wider in regions on the inside circumferential side. CONSTITUTION:The S/N of the reproduced signal is proportional to Wlambda (track width X minimum recording wavelength). Since the disc is rotated in a constant angular speed, the minimum value of the S/N of the reproduced signal is determined by the recording wavelength of the innermost track; and since the recording wavelength of tracks per one circle is longer on the outside circumferential side, the S/N of the reproduced signal is higher than required on the outside circumferential side. A width W1 of a recording track 2 is set to a half of a width W2 of a recording track 3, and the pitch of the recording track in the part of a region S1 is set to a half of that of the part of a region S2. Thus, W1lambda1 in the region S1 on the outsie circumferential side and W2lambda2 in the region S2 on the inside circumferential side are coincident with each other approximately when boundaries between regions S1 and S2 are determined properly, and therefore, the recording capacity is increased, namely, the recording time is extended as a whole by a length corresponding to doubling of the recording density in the region S1. Further, the S/N is held in a prescribed value or more. |
