Michinobu Mieda

Influence of birefringence on the signal quality of magnetooptic disks using polycarbonate substrates

Magnetooptic (MO) disks using polycarbonate (PC) substrates were investigated. Birefringences of the PC disk substrates molded with different methods were measured. Signal qualities for MO disks with the PC disk substrates were also measured and the effect of the birefringence on the signal quality was estimated.

Direct Overwriting Using Magnetooptical Trilayer Medium and One Magnet

The magnetooptical trilayer medium DyFeCo/GdFeCo/GdDyFeCo which is overwritable by light intensity modulation using a single permanent magnet has been developed. The carrier-to-noise-ratio (CNR) of the medium was 46 dB and the erasability was -37 dB when a 0.65-µm-mark-length signal was written over a 1.0-µm-mark-length signal.

New disc format for land/groove recording on magnetically induced super-resolution disc

We developed a new disc format for land/groove recording. The new disc had grooves wobbled on one side to obtain address information. We examined characteristics of signals reproduced from the wobbled grooves and a suitable groove shape for a double-layered magnetically induced super-resolution disc. By the use of the new disc format, good signal quality of address information is obtained on both lands and grooves. At a groove shape with 40 nm depth and 0.7 µm track pitch, a CNR of 47 dB and a crosstalk of -32 dB were obtained at the recorded mark length of 0.55 µm in magnetic field modulation recording.

Recording and readout using clock marks premastered by groove wobbling

A new recording and readout technique for land and groove recording on a magnetic super-resolution (MSR) disk is described. The technique uses specifically premastered clock marks. To generate a stable clock signal, the clock marks are fabricated with short bursts in grooves by wobbling at a different frequency from address information. The clock marks and the address information can be separated from a track error signal. When the extracted clock signal is applied to precise recording and readout of the magneto-optical data marks, the bit error rate becomes lower than that of the conventional clock recording/readout system. Additionally, the crosstalk of the wobbled address information to the magneto-optical signal can be canceled out electronically. This new format is not only suitable for high-density recording but also convenient in the disk manufacturing process.

Thermal Direct Mastering Technique Using a Deep UV Laser

The new mastering technique directly formed patterns in an organic material by heat was developed, and a high-density ROM disc of 100 GB recording capacity could be mastered applying a deep UV laser.