MAGNETO-OPTICAL RECORDING AND REPRODUCING DEVICE HAVING DOUBLE BEAM SPLITTER

摘要

PURPOSE:To increase the efficiency of light source power in a record/erasion mode and at the same time to obtain the high intensity of a reproduction signal in a reproduction mode, by using a beam splitter which has the polarized reflection factor or transmittance suited to the reproduction and record/erasion modes respectively. CONSTITUTION:A light source L1 for recording/erasion laser beam having a wavelength lambda1 (=780nm) is provided together with a light source L2 for reproduction laser beam of a wavelength lambda2 (=830nm) which is set in parallel to the source L1, a double wavelength DBS and a signal photodetecting system N. The DBS is produced by forming a multi-layer dielectric film ML of TiO2 and SiO2 on the sloping surface of a glass prism G and then adhering the same prism G close to the film ML. The reflection factor is set at >=70% to the wavelength lambda1 and at <=50% to the lambda2 respectively. Thus the DBS has a high output/input light intensity ratio to the polarized beam of lambda1 and a low ratio of said intensity to the polarized beam lambda2 respectively.