| 摘要 |
PURPOSE:To detect the split light without using a polarizer, etc. and to enable optical reading of information with good S/N, by making opposite the direction of polarization of >=2 light flux parts symmetrical to an optical axis and separately detecting the light fluxes. CONSTITUTION:A laser light flux via a relay lens 22 is reflected by a beam splitter 23 to be a linear polarized light and becomes a light flux which is split into two symmetrically with respect to an optical axis at 1/2 wavelength plates 24B, 24A where the transmitted light is polarized oppositely to each other. The light fluxes become reflected light fluxes in which the polarized plane is changed in accordance with the information on a magnetic disc 26 and separately detected at detectors 27A, 27B via the 1/2 wavelength plates 24A, 24B and beam splitter 23 to read in the information according to differential amplification. Through the optical constitution consisting of the beam splitter splitting the reflected light into two, which is unnecessary for a polarizer every split reflection light and simple and easy for the adjustment, the optical reading of information can be made in an excellent manner with 7<S/N light amount loss. |
