Overwriting photomagnetic recording apparatus having single light source and fixed-field generator

Claim 1

An overwriting recorder for use in photomagnetic recording apparatus in which a laser beam emitted from a single semiconductor laser is focused on a moving photomagnetic disk to increase the temperature of the disk and reduce the coercive force thereof for magnetizing the disk according to directions of externally applied magnetic fields thereby to record signals, said overwriting recorder comprising: a light intensity modulator for modulating said laser beam with a signal to be recorded to obtain light intensities corresponding to the recorder signal; and at least one fixed-field generator, having North and South magnetic poles which are disposed at two positions along the disk moving direction, wherein said field generator is disposed at a location displaced from a location of the focused laser beam on the disk, said generator is for applying said magnetic fields with permanently fixed intensities in mutually opposite directions to the disk at the two positions thereon, said two positions are determined by the light intensities of the modulated laser beam such that the coercive force of said disk varies with time according to the intensities of said modulated light beam and wherein overwriting of data can be achieved.