Masahisa Shinoda

Optical pick-up for DVD

The optical pick-up for DVD with CD compatibility is discussed. DVD players or DVD-ROM drives are strongly required to have the conpatibility with conventional CD for the comrcialization of DVD. However, the difference of the substrate thickness between DVD and CD causes the different spherical aberration and prevents the laser beam from being focused into a diffraction limt spot size with only one objective lens. Several types of optical pick-ups for overcoming this problg and the twin lens type optical pick-up which is one of these solutions, are introduced.

Analysis of Behavior of Focusing Error Signals in Astigmatic Method in the Scheme of Land–Groove Recording

We present the behavior of focusing error signals in a land-groove-type optical disk by theoretical analysis. A gain difference between focusing error signals from a land and a groove occurs because the focusing error signal from the land does not coincide with that from the groove. We also report the dependence of the gain difference on some factors, which are related to the intensity distribution of a laser beam. The physical format of digital versatile disk random access memory is used as a land-groove-type optical disk model. The simulation results show that coma aberration that distorts the intensity distribution unidirectionally causes a large gain difference.

Track error detection system with dual phase difference for super-resolution optical ROM disc

This paper presents a track error (TE) detection system for a readout of a higher-density super-resolution optical disc beyond Blu-ray Disc™, unaccompanied by its complication, based on a differential phase detection method. An improvement of quality of TE signal with this system is described on a numerical simulation using experimentally acquired a readout signal of the super-resolution optical disc.