Toshiaki Tsuyoshi

Sector Servo Data File Optical Disk Memory

Sector servo optical disk mass data storage system was designed. In this method each track is divided into 1024 sectors. Each sector consists of the preformated servo field and data field where data are recorded. One forth wavelength depth preformated servo field contains wobbled pits array from which tracking servo signal is generated. This tracking error signal is sampled and hold in the data field. This system has advantages of its compactness of optical drives and higly improved optical stability.

Degradation of recording performance in high-speed recording

Effects of dynamic coercivity on recording performance at write frequencies of 10-250 MHz and medium velocity of 20-50 m/s were investigated. It was found that degradation of signal-to noise ratio and roll off characteristics in high-speed recording is extremely small, and degradation of nonlinear transition shift is mainly due to the rise time of the magnetic field in the write head. Moreover, overwrite characteristics degrade significantly because of dynamic coercivity effects.

Number Of Sectors And Track Offset Suppression Performance In The Composite Wobbled Tracking Optical Disk

The new tracking method named composite method is analyzed both theoretically and experimentally. It is found that this type of disk realizes high optical stability and accurate track following, which is not influenced by optical head characteristics. The composite method, a conbination of the push-pull and the wobbled tracking method, has the number of wobbled sectors in the order of 16-32. In this method, the wobbled tracking technique is used to suppress the low frequency offset component in the push-pull tracking error signal due to aging or soiling of the optical system. The relation between the number of sectors, track offset suppression performance and influence of missampling were simulated by servo simulator; the results were found to be quite consistent with the experimental results.