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. 16, 1980
Filed:
Dec. 26, 1978
Antonius A Van Alem, Eindhoven, NL;
Cornelis H Vos, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
Abstract
An apparatus for reading a disk-shaped record carrier, the radial scanning position being controlled with the aid of a first servo control loop, which controls a positioning member for the read element depending on a control signal which is read from the record carrier. If this control is disturbed a second servo control loop is rendered operative. This second servo control loop comprises a position indicator for supplying a position signal which is representative of the radial position of the positioning member, a memory circuit for storing the value of this position signal at the instant of failure of the first servo control loop, and a differential amplifier for applying a control signal to the positioning member, which signal corresponds to the difference between the instantaneous and the stored value of said position signal. Furthermore, there is provided a control circuit for changing-over between the first and the second servo control loop and vice versa depending on a built-in criterion.