Sensing previously-recorded information while recording or erasing a magnetooptic storage number

A method of recording and reading information on a magnetooptical recording medium having a magnetooptical recording layer with Curie point below which magnetic remanence of said recording medium is stable and above said Curie point the magnetic remanence of said recording layer is unstable, a magneto-optical recorder-player having a laser means for irradiating a laser beam onto a beam illuminated area of said magnetooptical recording layer for gradually heating said beam illuminated area to a temperature above said Curie point, said optical recorder-player having a magnetic biasing means for providing a magnetic bias field to the recording layer at said laser beam illuminated area having a first magnetic polarity, said beam illuminated area reflecting at least a portion of said irradiated laser beam said laser beam having a rotatable linear polarization and said recording layer reflecting said layer beam to a detection means, said recording layer rotating the linear polarization of the reflected laser beam using a Kerr effect;

• comprising the steps of:
• activating said laser means to irradiate said laser beam onto the recording layer to said laser beam illuminated area of the recording layer encompassed by said magnetic bias field and having an intensity to gradually heat the beam illuminated area of the recording layer receiving the laser beam to a temperature above the Curie point;
• moving the recording medium and the laser beam relative to each other so that the laser beam scans a track on the recording layer at a rate wherein the laser beam illuminated area on the recording layer has a leading portion in which temperature remains below the Curie point and a remaining portion of the beam illuminated area having a temperature above the Curie point;
• and
• sensing said laser beam reflected from the leading portion of said laser beam illuminated area and analyzing the reflected laser beam to indicate a direction of said remanent magnetization.

A magnetooptic recorder-player having laser and optical means for shining a single laser beam onto a magnetooptic recording layer in a storage member, said recording layer having a Curie point, a plurality of tracks in the recording layer for recording data;

• the improvement including, in combination:
• mover means coupled to the storage member for relatively moving the storage member and the laser and optical means at a predetermined relative speed for causing the single laser beam to scan a track on the recording layer at said predetermined speed;
• first means in the recorder-player coupled to the laser and optical means for actuating said laser and optical means to emit said single laser beam to illuminate an area of said track during said scanning, said laser beam having an intensity sufficient for sensing any recorded information in the recording layer for heating the illuminated area in said recording layer to a temperature below said Curie point whereby a current direction of remanent magnetization in said track is sensed without reversing said remanent magnetization, said illuminated area reflecting said laser beam as a first reflected laser beam;
• second means in the recorder-player coupled to the laser and optical means for actuating said laser and optical means to emit said single laser beam with a light intensity for gradually heating said illuminated area for creating a leading portion of the illuminated area having a temperature less than said Curie point of said recording layer and creating a remaining portion of the illuminated area having a temperature in said recording layer greater than the Curie point, said leading portion reflecting said laser beam as a second reflected laser beam;
• magnetic biasing means for supplying a magnetic bias field to said illuminated area having a given magnetic polarity for biasing the magnetization direction in said remaining portion to said given magnetic polarity;
• and
• reading means operatively coupled to the laser and optical means for receiving said first and second reflected laser beams for reading information recorded in the recording layer of the storage member.