| 摘要 |
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.
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