MAGNET HAVING CONCAVE PATTERNS AND AN OPTICAL PICKUP ACTUATOR COMPRISING THE MAGNET, PARTICULARLY WITH REGARDS TO INCREASING A MAGNETIC FLUX DENSITY CONCENTRATED ON A COIL

摘要

PURPOSE: A magnet having concave patterns and an optical pickup actuator comprising the magnet are provided to symmetrically dispose plural concave patterns where a curvature radius of an opening circle of a magnet is bigger than a curvature radius of a subsiding circle, thereby increasing a magnetic flux density reaching an available coil. CONSTITUTION: Plural concave portions(13) are symmetrically distributed on a surface of a flat magnet(11). Supposing that a curvature radius of an opening circle of the concave portions(13) is 'r' while a curvature radius of a subsiding circle is 'd', the curvature radius 'd' of the subsiding circle is smaller than the curvature radius 'r' of the opening circle. Intervals among the concave portions(13) are bigger than the curvature radius.