Masaaki Matsumaru

Combined adaptive controlled PRML signal processing for high-density optical disk

The combined adaptive controlled PRML signal processing was newly developed. The new method is a combination of the adaptive controlled FIR filter and the adaptive controlled Viterbi decoder. The adaptive controlled Viterbi decoder was operated under the condition that the Viterbi decoder is controlled such that the unity gain is kept. We report the simulation results, which are evaluated using signal asymmetry margin and tangential tilt margin to verify the effectiveness of this method expanding the margins. The combined adaptive controlled PRML signal processor is effective for these signal tolerances. Furthermore, the experimental results confirm the simulated effectiveness for expanding the tangential tilt margin. Consequently, a new method of combined adaptive controlled PRML signal processing is effective in reducing the deteriorations of data detection for high-density optical disk.

Transition Mechanism of WOx Available for Optical Disc by Laser Irradiation

WOx thin films are one of the candidates for the recording layer of write-once optical discs and the inorganic photoresist material used in heat-mode mastering. We have investigated the transformation mechanism of WOx during laser irradiation. As a result, we observed changes in the volume and crystallinity of WOx film. We conclude from various analyses that the solubility of WOx film in alkali solution may sensitively depend on the atomic ordering determined by deposition conditions or laser exposure conditions.

High-Density and High-Carrier-to-Noise-Ratio Optical Disk Mastering

A scanning tunneling microscope (STM) was used to observe the surface profile of an optical disk and to quantitatively evaluate the lithography conditions in the mastering process. A high-density and high-carrier-to-noise-ratio (C/N) optical disk was achieved using precise data concerned with the relations among the mastering process, the profile of the masters, and the readout signal.

Combined Adaptive Controlled Partial Response and Maximum Likelihood Signal Processing for High-Density Optical Disks

The partial response and maximum likelihood (PRML) signal processing method is effective for fabricating high-density optical disks because it allows inter-symbol interference in decoding. However, some deterioration factors, namely impulse response fluctuations and signal level fluctuations, still exist even though PRML signal processing is adopted. A combined adaptive controlled PRML signal processing method is proposed to surmount the problem of these two deterioration factors simultaneously. The key points of the combined adaptive controlled PRML signal processing are that the gain of the Viterbi decoder is unity and the expected signal takes into account the reference levels controlled in the adaptive controlled Viterbi decoder. The effectiveness of such processing is confirmed using simulated reproduced signals and actual reproduced signals. The characteristics in terms of the tangential tilt of the disk and the signal asymmetry are ameliorated by adopting the combined adaptive controlled PRML signal processing method.