The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 08, 1993
Filed:
Sep. 26, 1989
Hitachi, Ltd., Tokyo, JP;
Abstract
A recording medium is provided with a recording film having opto-magnetic characteristics formed on the substrate, with first information being recorded in advance in the form of pit strings of a phase structure. Second information is recorded over the first information through the application of a magnetic field with polarities corresponding to the second information in the presence of the irradiation of a high-power radiation beam, without damaging the record of the first information. The first and second information are produced independently and simultaneously with a single spot in the same area by use of different signal reproduction mechanisms for the first information and second information. The first information (ROM information) is reproduced as the variation in the amount (intensity) of the reflected light from the opto-magnetic recording film, and the second information (RAM information) is reproduced by detecting the rotational angle of the reflected light, based on the Kerr effect, from the opto-magnetic film concurrently with the reproduction of the first information using a single spot.