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:
Nov. 12, 1997
Tsutomu Matsui, Tokyo, JP;
NEC Corporation, , JP;
Abstract
According to an astigmatic difference correcting method for an optical head, a rotational optical member which is arranged between a first laser beam source having an astigmatic difference and a collimator lens to be rotatable around an optical path of a laser beam of a first wavelength emitted from the first laser beam source is rotated and adjusted. Rotation and adjustment of the rotational optical member is caused to set a minimum difference between focal positions in an X-axis direction and in a Y-axis direction which are perpendicular to the optical path of the laser beam. The laser beam in which the difference between the focusing offset positions is minimum is irradiated on an optical disk having a recording density having a bit length not more than half a laser wavelength.