Kouichirou Wakabayashi

Crosstalk reduced by new types of optical filtering

It is found that there is the region in the exit pupil of the objective lens where waveform polarity of crosstalk from adjacent tracks is inverted from that of total crosstalk. Additionally, the regions that contribute to the total signal of fine mark pattern are separated into two regions with a gap remaining along the radial direction of the disk. Shading or polarity inversion in the region neither this signal region nor inverted crosstalk region reduces the crosstalk from adjacent tracks without reducing the signal of a fine mark patterns.

High-density recording by two-dimensional signal processing

To make higher density on optical disk, a new recording method- 2D recording-which can increase the track-density rather than the linear density was proposed. The performance of this method on increasing density is estimated by the simulation and confirmed by measuring the read-out signal. Consequently, it is clarified that this method can attain more than twice the areal density independently and realize the density of 2.2Gbit/in2 which is 8 times as large as that of first generation using 680 nm laser diode.