| 摘要 |
PROBLEM TO BE SOLVED: To improve the SN ratio of a tracking error signal by dividing the light reception surface of a first photo detector into a direction corresponding to the scan direction of a laser beam and a direction for orthogonally crossing it, and by increasing the quantity of return light that enters the first photo detector in proportion to that of return light that enters a second photo detector. SOLUTION: Return light enters the inside of a prism 34 from the slant of the prism 34, and reflection is repeated in the inside for receiving light from light reception surfaces 33A and 33B. For the return light, the quantity of light is transmitted by the lower surface of the prism 34 by 80% and is received by the light reception surface 33A, the remaining 20% quantity of light is reflected by an upper surface and enters the lower surface, and the quantity of light is transmitted by 100% and is received by the light reception surface 33B. As a result, in an optical integrated element 24, the drastically larger return light enters the light reception surface 33A at a front side being used to generate a tracking error signal by the DPD method as compared with the light reception surface 33B at a rear side. |
