Magneto optical overwriting methods using a single optical head designed for a two-beam overwrite

Claim 1

A method for overwriting information in a magneto-optical memory layer, comprising the steps of: a) providing a magneto-optical memory substrate with the magneto-optical recording layer having a perpendicular magnetization direction characteristic coated thereon, the magneto-optical recording layer having information tracks, each of which carries previously selectively recorded magnetic domains; b) providing a first optical system including a first laser and an object lens for irradiating the magneto-optical recording layer with an erasing light beam, and a second optical system including a second laser and the object lens for irradiating the magneto-optical recording layer with a writing light beam; c) irradiating the erasing light beam onto one information track of the information tracks, regardless of the presence or absence of written information in the information tracks, the erasing light beam having a power sufficient to erase the written information but not sufficient for writing information in the information track; and d) selectively irradiating the writing light beam in accordance with information to be overwritten into the erased information track of the information tracks, the writing light beam having a power sufficient for writing information into the information track, the erasing and writing light beams being focused through the objective lens on the information tracks closely adjacent to each other such that a distance between light beam spots formed on the information track by the erasing and writing light beams is approximately 10 μm to 50 μm.

Claim 2

A method for overwriting information in a magneto-optical memory layer, comprising the steps of: a) providing a magneto-optical memory substrate with the magneto-optical recording layer having a perpendicular magnetization direction characteristic coated thereon, the magneto-optical recording layer having information tracks, each of which carries previously selectively recorded magnetic domains; b) providing a first optical system including a first laser and an object lens for irradiating the magneto-optical recording layer with an erasing light beam, and a second optical system including a second laser and the object lens for irradiating the magneto-optical recording layer with a writing light beam; c) irradiating the erasing light beam onto one information track of the information tracks, regardless of the presence or absence of written information in the information tracks, the erasing light beam having a power sufficient to erase the written information but not sufficient for writing information in the information track; and d) selectively irradiating the writing light beam in accordance with information to be overwritten into the erased information track of the information tracks, the writing light beam having a power sufficient for writing information into the information track, the erasing and writing light beams being focused through the objective lens on the information tracks closely adjacent to each other such that a distance between light beam spots formed on the information track by the erasing and writing light beams is approximately 10 μm to 50 μm.