OPTICAL RECORDING AND REPRODUCING DEVICE

摘要

PURPOSE:To start recording of the new information almost concurrently with the start of erasion of the old information in a rerecord mode, by using a magnetic bias adding device which generates magnetic fields of opposite directions to each other at positions of two minute light spots for record and erasion respectively. CONSTITUTION:A magnetic pole near a minute light spot 13 for erasion is magnetized to an S pole; while a magnetic pole near a minute light spot 14 is magnetized to an N pole. Thus external magnetic fields of Z and -Z directions are formed at positions of spots 13 and 14 respectively. These positions 13 and 14 in those external magnetic fields are heated up to a level higher than the Curie point defined in accordance with the characteristics of an information recording medium 1. Thus the local magnetization of the medium 1 is reset to the initial state of the Z direction by the position of the spot 13 to secure an erasion state and then inverted in the -Z direction by the position of the spot 14 to form a minute domain of about several mum with a record state. Therefore a rerecord state is obtained in response to the shift of an optical head.