| 摘要 |
PURPOSE:To reduce noises and detection errors so as to improve the S/N in the readout of information, by providing a transmitted light quantity reducing means which reduces the quantity of transmitted light against linearly polarized light except a prescribed area including the optical axis of the linearly polarized light. CONSTITUTION:A collimate lens 6, polarization beam splitters 8 and 10, Faraday rotor 12, slit 14, and object lens 16 are provided in the incident optical path from a semiconductor laser 2 to a magneto-optical disk 4. The slit 14 is set in front of the object lens 16 so that the laser light made incident to the lens 16 can be limited to the laser light having planes of polarization normal to or parallel with the plane of incident. Therefore, the plane of polarization of the laser light does not rotate before and after the lens 16 and only Kerr rotation can be caught as the rotation of the plane of polarization. As a result, noises and detection errors can be reduced and the S/N ratio in information reading-out can be improved.
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