| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical pickup capable of detecting tracking error signals of different systems by using a single optical pickup. <P>SOLUTION: A diffraction grating element 3 used for the optical pickup of this invention is at right angles to the optical axis 9 from semiconductor laser, and is also divided into four parts by a straight line 1 parallel to the tangential direction of an optical disk 1 and a straight line 12 parallel to the radial direction thereof, and are defined as the 1st to 4th areas in the passing direction of pit string on the surface of the optical disk 1, namely, clockwise from the upper left side on this paper. A hologram 13 formed on the 1st area and a hologram formed on the 2nd area are formed so as to have different focal points in the plane including the optical axis 9 and the straight line 12, and have different diffraction angles from each other. The same diffraction patterns as the holograms 13, 14 are alternately positioned in the divided areas 3a to 3e and 4a to 4e composing the 3rd and 4th areas, respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
