Importance

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Abstract

The present invention includes a method and apparatus for reducing the effective spot size of a laser beam by selectively polarizing different regions of a light beam. By suitably dividing a beam into a plurality of regions and suitably changing the polarization of the regions in different directions, certain regions with opposite polarization cancel each other out, thereby effectively eliminating these regions from analysis by the detector. When focusing onto a high density optical disk, adjacent tracks do not see the canceled, circularly-polarized portions of the beam, but instead, only see the smaller, plane-polarized portion in the center of the beam. When reading from a high density optical disk, detectors using a known differential detection scheme similarly do not see the canceled, circularly-polarized portions of the beam, but instead, only see the smaller, plane-polarized portion in the center of the beam.

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First Claim