| 摘要 |
PURPOSE:To erase assuredly an optional information bit and at the same time to attain the reduction of number of component parts and miniatruziation as well as the easy control of an optical system for a photo-magnetic recorder, by providing a laser beam irradiating means for both record and erasion and a magnetic field generating means which produces an adverse magnetic field which is larger in an erasion mode than that in a record mode. CONSTITUTION:The record and erasion are carried out by a permanent magnet 9 and an optical system 8 serves as a laser beam irradiating means for a record thin film 7 consisting of a photo-magnetic disk fixed to a rotary mechanism. The direction of a magnetic field is opposite to each other between the record and erasion modes, and therefore the magnet 9 is turned by revolving shaft 10 to perform inversion of the magnetic field. In this case, the intensity of magnetic field is varied for the shaft 10 since the center of the magnet 9 is shifted. The distance between the film 7 to the end surfac of the magnet 9 is set at 17mm. and 9.2mm. for record and erasion respectively in order to obtain magnetic fields of 150Oe and 400Oe on the film 7 in record and erasion modes respectively. Thus it is possible to obtain the desired intensity of magnetic field by shifting the shaft 10 by 3.9mm. from the center of the magnet 9 since the magnet 9 has 10mm. thickness. |
