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. 02, 1999
Filed:
Sep. 22, 1997
Toshihisa Tanaka, Yokohama, JP;
Nikon Corporation, Tokyo, JP;
Abstract
A data recording and playback device to perform focusing control on each recording layer of a multi-layer recording medium having a plurality of recording layers. The data recording and playback device includes a focus control device having a focusing movement device to set a position of a light spot, which illuminates a data recording medium having a plurality of recording layers, with respect to a direction perpendicular to the data recording medium. A focus error signal forming device forms a focus error signal based on a relative displacement of the position of the light spot set by the focusing movement device and the recording surface of the medium. A position signal forming device forms a position signal based on a displacement of the focusing movement device in a direction perpendicular to the recording medium surface, the position signal forming device having a detection range wider than that of the focus error signal forming device. A control device forms a control signal at the time of a focus jump operation to move the light spot from a recording layer to a target recording layer based chiefly on the position signal, and forms a control signal to control the focusing movement device at the time of a focusing operation to move the light spot to follow a target recording layer based chiefly on the focus error signal.