| 摘要 |
A magneto-optical head device includes a semiconductor laser, an objective lens system, a diffractive element, photodetectors, and an analyzer. The diffractive element has diffraction efficiency dependent on a polarization direction of incident light. The photodetectors receive the light reflected from a magneto-optical disk and diffracted at the diffractive element. The analyzer splits at least a part of the diffracted light from the diffractive element into two polarized components orthogonal to each other. The diffractive element has characteristics with which the polarized component in a predetermined direction in the incident light is partially diffracted and the polarized component orthogonal thereto is substantially totally diffracted. The diffractive element is disposed such that the polarization direction of the light emitted from the semiconductor laser coincides with the predetermined direction, and the analyzer is disposed such that the two polarized components split by the analyzer make an angle of about 45 DEG with respect to the polarization direction of the light emitted from the semiconductor laser. The amounts of the main polarization component beams that reach the two photodetectors can be made substantially equal with each other and the common-mode noise elimination ratio during the differential detection operation can be raised. Also, the ratio of the magneto-optical signal component that reaches the photodetectors used for magneto-optical signal detection can be raised.
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