25 GB Read-Only Disk System using the Two-Dimensional Equalizer

Abstract

In order to achieve a higher density disk system, we applied a two-dimensional equalizer along with a limit equalizer to an optical disk drive system which has an objective lens with a numerical aperture of 0.85 and a thin transparent cover layer of 0.1 mm thickness. Consequently we realized the 25 GB read-only disk system with sufficient margins against disk tilt and defocus. The two-dimensional equalizer is composed of a cross-talk cancel system and a tangential adaptive equalizer, and could prevent deterioration due to inter-symbol interference and cross-talk from adjacent tracks. Using the limit equalizer could prevent deterioration due to disk noise. By measuring the jitter with the limit equalizer, which has an ability to expand the system margin almost equivalent to that of the Viterbi decoder, we could evaluate the disk quality for standardization and verification.