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:
Dec. 06, 1994
Filed:
Dec. 28, 1992
Franciscus J Greidanus, Yorktown Heights, NY (US);
Johannes H Spruit, Eindhoven, NL;
Bernardus A Jacobs, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
Abstract
A method and apparatus for writing and reading information in the form of a pattern of magnetic domains in an information layer of a record carrier. An optical scanning beam is focused to a diffraction-limited radiation spot, and a magnetic field is generated by a coil supplied with an energizing current the amplitude of which is modulated by the information signal to be recorded. The magnetic field is thereby modulated, and produces magnetic domains in the information layer such that each domain has a variable number of sub-domains and consequently a variable magnetization ratio, as determined by the information signal. This permits recording at an information density exceeding that corresponding to the size of the radiation spot.