| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical head device which has a large ratio of a light quantity used for detecting an information signal recorded in a disk and a track error signal according to a phase difference method to the quantity of the light reflected from the disk, and can obtain high SN ratios concerning these signals. <P>SOLUTION: The light reflected from the disk 6 is diffracted by a hologram optical element 7 and is received by a photo-detector 9. A focus error signal is detected from the negative primary diffracted light of the hologram optical element 7, and the track error signal by the phase difference method, a track error signal by a push-pull method, and the information signal recorded in the disk 6 are detected from the positive primary diffracted light of the hologram optical element 7. A diffraction efficiency of the positive primary diffracted light is higher than that of the negative primary diffracted light. <P>COPYRIGHT: (C)2004,JPO |
