| 摘要 |
PURPOSE:To improve efficiency of utilizing light. CONSTITUTION:High-density double diffraction gratings 7 formed by superposing two pieces of high-density diffraction gratings on each other are so arranged on the optical path between a light source 5 and a recording medium 1 in such a manner that the exit light from this light source 5 is polarized to P polarized light. The light transmitted through the double diffraction gratings 7 is circularly polarized by a quarter-wave plate 8 and is condensed to the recording medium 1 by a condenser lens 1 so that the recording medium is irradiated with this light. The reflected light returning through the same optical path from the recording medium 1 is passed through the quarter-wave plate 8 and is polarized to S polarized light which is made incident on the double diffraction gratings 7 and is thereby diffracted. A focus error signal, track error signal and RF signal are detected from the diffracted light. |
