Kenjiro Kime

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.

Development of the moving magnet type two dimensional actuator in optical disk drives.

This paper presents a lens actuator of optical head in an optical disc drive. A newly developed moving magnet method is applied to a two dimensional sliding and rotary lens actuator, and radically simplified. This method is to compose a magnetic suspension in focusing and tracking direction by means of yokes and a ring-shaped magnet magnetized in four pole at unequal intervarls, and the designing method of magnetic suspension is disclosed by a detailed magnetic field analysis. It has been further confirmed by analysis and experiment that the force in an undesired direction caused by movement of the magnet can be reduced by symmetrical magnetization. As a result, in driving force, control band and other characteristics, the same performance as in the moving coil type have been recognized.