Radial tilt adjustment method with Partial Response Signal-to-Noise Ratio (PRSNR) was newly developed. This method is able to adjust radial tilt rapidly, because the method uses the detected signal with polarity to radial tilt. Furthermore, the method has the accuracy of adjustment within ±0.1 degree, which is enough for HD DVD.
High density land/groove recording, using partial response maximum likelihood (PRML) technology, which corrects errors in the readout signal for exploiting readout channel characteristics, has been developed. By this detection method, both land area and groove area can be used for data storage tracks without a crosstalk cancellation technique. Applying this method with a red laser, 8 times the storage capacity, compared with the conventional method, has been achieved.
High track density magneto-optical recording, using a crosstalk canceller which eliminates crosstalk from two adjacent tracks, has been developed. By this recording method, both land area and groove area can be used for data storage tracks, and twice the track density, cornpared with the conventional method, has been achieved. Applying this crosstalk canceller also realizes intersymbol interference compensation.
A magnetic field modulation overwrite technique has been developed for magneto-optical (MO) disks using an active head-to-disk spacing control method, that detects the distance between the magnetic head and the recording layer and holds it constant. This method achieves magnetic field modulation overwrite for MO disks, that solves headcrash problem, makes it easy to remove disks and provides constant recording characteristics, even for large axial deflection disks.