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:
Jan. 31, 1989
Filed:
Apr. 29, 1987
Daniel C Kowalski, Portola Valley, CA (US);
Dan S Bloomberg, Palo Alto, CA (US);
Xerox Corporation, Stamford, CT (US);
Abstract
A magneto-optic optical disc system which uses the magneto-optic differential data detection channel, with addition only a low pass filter, to also detect focus error. The differential data detection channel includes a pair of photodetectors, the first photodetector being located a predetermined distance within the focal length of the detector lens associated with that photodetector and the second photodetector being located beyond the focal length of the detector lens associated with that photodetector. The output of a differential amplifier receiving the photodetector outputs is the data signal and the output of a low pass filter connected to the output of the differential amplifier is the focus error signal. The dual functionality of the differential data detection channel eliminates a separate optical focus channel, and relative to separate astigmatic focus and data detection channels elmininates a quadrature detector, several optical elements, several electrical elements, and the space they occupy.