| 摘要 |
PURPOSE:To improve greatly utilization effect of light with less elements by using a means for deciding on whether an individual angle to an S component of a polarization beam splitter is generated or not by magnetic Kerr effect together with the polarization beam splitter. CONSTITUTION:On an optical path between an optical system 20 and a vertical magnetic recording body, e.g. magnetic disk 27, the polarization beam splitter 28, a polarization plane rotating means 29, a quarter-wavelength plate 30, and an objective lens 31 are arranged in order and a photodetector 33 is provided to photodetector a light beam from the polarization beam splitter 28 through a unidirectional lens 32, thus constituting this invented device. The light beam from the means 29 is made into a circular polarized beam through the quarter- wavelength plate 30 and the beam is passed through the objective lens 31 and also reflected totally by a surface of the magnetic disk 27 containing vertical magnetic record uner the magnetic Kerr effect to obtain an elliptic polarized light beam. After the beam passes through the polarization plane rotating means 29, side surfaces of the beam coincide with S components of the polarization beam splitter completely to perform extremely excellent reflection, and the beam reaches the photodetector. |
