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:
Sep. 10, 1985
Filed:
Mar. 10, 1983
Masuo Oku, Kamakura, JP;
Masami Yamashita, Yokohama, JP;
Yoshio Miura, Yokohama, JP;
Motoyuki Suzuki, Yokohama, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A focus servo system for an optical video disc player. A pair of signals generated by two pairs of photo-cells are supplied to an adder and a differential amplifier, an output signal of the adder is supplied to a first comparator and an output signal of the differential amplifier is supplied to a second comparator. When an output signal of the adder reaches a reference voltage of the first comparator, a focus servo pull-in range is detected. Thereafter, when an output signal of the differential amplifier reaches a reference voltage of the second comparator, a stable operation condition of the focus servo system is detected and a servo system loop is closed so that a malfunction is prevented.