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. 13, 1987
Filed:
Jul. 22, 1983
Pioneer Electronic Corporation, Tokyo, JP;
Abstract
In a system for optically reading out information recorded on a recording medium, the focus servo device includes an object lens supported by a resilient support member and a focus servo loop. The focus loop includes a driving current generating means for generating a driving current of a cylindrical coil of a focus actuator connected to the object lens in accordance with an output signal of a pickup means which includes the object lens. The improvement is that the dc loop gain of the focus servo loop is substantially raised to infinity, so as to reduce the magnitude of the focus error signal which is required to produce the driving current of the cylindrical lens for moving the object lens against the resilient force of the support member. Further, the focus servo device is characterized by a phase retarding circuit for reducing the amount of the phase rotation at the higher frequency range so as to assure the stability of the operation of the focus servo loop.