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:
Aug. 08, 2000
Filed:
Nov. 26, 1997
Toshihisa Tanaka, Yokohama, JP;
Hiroshi Arai, Yokohama, JP;
Nikon Corporation, Tokyo, JP;
Abstract
A focus control device to perform focus control for a multi-layer recording medium having a plurality of recording layers. The focus control device includes an illuminating device to illuminate an information recording medium having a plurality of recording layers with a converged light beam, a focusing device to set a focus position of the converged light beam in a direction perpendicular to the recording medium surface, and a tracking device to set an illumination position of the converged light beam in a radial direction on the medium. A control unit controls the focusing device and tracking device to perform a seek operation to move the illumination position of the light beam to a target track of a target recording layer. The control unit controls the focusing device and the tracking device to change from a track following control state to a movement control state in which the illumination position of the light beam is moved in the radial direction of the medium while the focus position of the light beam is moved in the direction perpendicular to the medium to move to a target recording layer and track. The control unit returns the focusing device and tracking device to a track following control state when the illumination position of the light beam is in the neighborhood of the target track of the target recording layer.