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:
Nov. 17, 1992
Filed:
Sep. 28, 1990
Alan A Fennema, Tucson, AZ (US);
Robert A Klem, Tucson, AZ (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
A focus acquisition system includes providing a focus offset and changing the offset symmetrically for each measurement cycle. The amplitudes of the readback or tracking error signal are sensed and compared. When the amplitudes of the tracking error or readback signal is different at each of the offsets, then a new measurment cycle is performed after calculating a new offset value. The process is repeated until the temporary measurement offsets result in readback amplitudes that are substantially equal. A best focus is then indicated as being a position in which small defocussing will not substantially degrade the quality of the readback signal.