| 摘要 |
PURPOSE:To suppress the generation of laser noises regardless of the variance or variation of the retardation of an optical information recording medium, by using a phase difference compensator and a control means for compensated phase difference. CONSTITUTION:The luminous flux passed through a phase difference compensator 4 receives a phase difference at the polarization component of the main axial direction of the compensator and is condensed on an information recording surface 7 formed on an optical information recording medium 6 like an optical disk, etc. having the retardation characteristics through an objective lens 5 in the form of the circular polarized light or the oval polarized light. The condensed light is reflected to be turned into the return light and passes through the lens 5 and the compensator 4 again to reach a polarized beam splitter 3. The quantity of the light fed back to a semiconductor laser 1 can be controlled to the optional value by changing the compensated phase difference of the compensator 4 in response to the amount of retardation of the medium 6. A compensation plate of Babinet Soleil is used to the compensator 4.
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