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. 29, 1983
Filed:
Jun. 29, 1981
William E Barnette, Levittown, PA (US);
Robert W Jebens, Skillman, NJ (US);
RCA Corporation, New York, NY (US);
Abstract
A focus servo system for optical disc record/playback apparatus includes three current drivers for maintaining the distance between an objective lens and an information surface of the disc substantially constant. One driver is a DC to low frequency amplifier which can drive the transducer over its full range to the mechanical stops. The second current driver is a DC to high frequency amplifier whose output at DC is limited to drive the transducer approximately twice the expected disc runout. At higher frequencies, the output is such that the displacement of the transducer does not exceed the displacement corresponding to DC value. In operation, the low frequency driver adjusts the DC operating point of the high frequency driver so that its output averages to approximately zero, thus decreasing the drive requirements of the high frequency driver. The third driver is a DC current source which sets the static operating point of the transducer.