| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a technology for performing proper focus position control by a prepit even when there is an astigmatism or the like in an optical head in an optical disk unit. <P>SOLUTION: The optical system of an optical head is constituted by having an astigmatism of a size of about 0.03λrms or less, and of an inclination to an optical axis of about 45°wherein λ is the wavelength of a recording or reproducing laser beam. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
