The partial response channel, which is recently applied to high density recording, is designed based on the linear channel. Since, the high linear density signal of perpendicular magnetic recording is well represented as the superposition of the isolated pulse. PR will be suitable for perpendicular magnetic recording. Although we have found that this superposition does not precisely hold over 100 kFRPI, newly developed "bi-layered main-pole type head" is effective against this problem. As a result, we can demonstrate the 200 kFRPI data read/write with error rate of 10^<-4>.

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An inductive head for recording and a yoke type MR head for playback apply to the DCC system. It is difficult to fabricate these heads on the same substrate and to control the head properties. Therefore we have developed a new combined type thin film head. The new combined structure of our head leads to the reduction of the production process and also this head proved applicable for DCC.

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In order to increase the capacity for second generation magnet-optical disk, combination with zoned CAV and mark edge method is suitable. When adopting mark edge method to magneto-optical media a new write control method that thermal distribution on recording layer can be controlled, and pre-write testing method that can form a precise shape of mark independent on environmental temperature are developed. These technologies are applicable for zoned CAV that a clock frequency varies with a radius position. Developed read/write circuits and control method are usable for non overwrite media and also overwrite media Using these technologies it is proved that high density, 880 Mbit/in can be realized by non overwrite media.

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New method for analyzing the read signal from magneto-optical (MO) disks, which use mark-edge recording method is studied. We find that the read signal from several magnetic domains can be obtained by superposing the signal from each domain, based on the detection principle of MO. Superposing method of the step waveform of the leading and trailing edge of domain, is useful for simulating the read process of the mark-edge recording, especially in the case where width of each domain is well controlled.

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We have developed a new equalizing method using an artificial neural network to get higher density read-out and to garantee greater margin of coma and defocus. In this method. the neural network is trained to eliminate intersymbol interference and aberrations. The neural-net equalizer(NNEQ) offers advantages over the coventional linear transversal equalizer. And the NNEQ, combined with numerical aperture of 0.60 objective lens and wavelengh of 670 nm laser, allows playback of discs with quadruple density of CDs.

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