| 摘要 |
PURPOSE:To obtain an excellent S/N ratio and detect an error signal regarding focusing and a track efficiently by optimizing the transmission efficiency of an incident polarization-directional component to a disk. CONSTITUTION:A beam splitter 40 separates reflected light from an photomagnetic disk 40 having a track guide groove into spectral components, which are guided to an optical path different from that of incident light from a semiconductor 401. Then, a beam splitter 408 splits a light beam guided to another optical path into two; one is used to detect an error signal for focusing and track matching, and the other is used by a polarizing prism 411 for differential detection. Then, the transmission efficiency of photomagnetic disk incidence-directional components of the splitters 404 and 408 is limited to make a dominant noise in an in-use frequency band into a shot noise, obtaining the excellent S/N ratio. |
