| 摘要 |
An optical pickup including a light source, a light focus device, a diffraction element, an optical split element, a ¼ wavelength board, a light reception device and a correction element wherein the correction element is divided into multiple areas in a surface vertical to an optical axis, each area of the multiple areas has a sub-wavelength convexo-concave structure having a pitch equal to or shorter than a wavelength of the outgoing light beam and the sub-wavelength convexo-concave structures of the multiple areas adjacent to each other have groove directions perpendicular to each other, and the filling factors of adjacent areas of the multiple areas are determined to substantially equalize effective refractive indices with regard to the polarization direction of the outgoing beam emitted from the light source and impart a phase difference of &pgr; with regard to a polarization direction perpendicular to the polarization direction of the outgoing beam.
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