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:
Jul. 04, 1995
Filed:
Feb. 16, 1994
John E Bish, Tucson, AZ (US);
David E Call, Hollister, CA (US);
Glen A Jaquette, Tucson, AZ (US);
Judson A McDowell, Tucson, AZ (US);
Arturo A Mojica, Tucson, AZ (US);
Lawrence D Tipton, Tucson, AZ (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
The present invention provides a method and an apparatus to accurately and consistently distinguish blank sectors from written sectors on optical media despite drive and media variations. A readback envelope threshold is established each time optical media is mounted into an optical drive. In one embodiment, the gain of readback amplifiers are set to a first level, the optical head seeks to and reads a sector or set of sectors on the optical disk known to have information recorded thereon and a first readback envelope generated. The gain off the readback preamplifier is then set to a second level, the optical head seeks to and reads another sector or set of sectors known to have information recorded thereon and a second readback envelope generated. The readback threshold is calculated from the amplitudes of the first and second envelopes. Once the threshold has been calculated for a disk, the drive can scan for a blank sector by comparing the amplitude of the sector's readback envelope with the threshold: if the amplitude is less than the threshold and no other written format feature is readily indicated, the sector can be classified as being blank and it is safe to write to the sector.