Patent ID: 7417936

Claim:
An optical pickup compatible with an optical information storing medium, comprising: a laser light source; an objective lens which focuses a light emitted from the laser light source on the optical information storing medium; an optical path changer which changes a proceeding path of the light emitted from the laser light source; a quarter wave plate made of a plurality of wave plates having a plurality of optic axes arranged offset from a line perpendicular to a plane of the wave plates in opposite directions so that a phase difference according to an incident angle of light is offset and corrected, the quarter wave plate changing a polarization of an incident light to make the polarization of a light reflected by the optical information storing medium and reentering the laser light source different from the light emitted from the laser light source, such that the light emitted from the laser light source is changed to circularly polarized light as it passes through the quarter wave plate, then the light reflected by the optical information storing medium is changed to a circularly polarized light orthogonal to that of the light emitted from the laser light source and passing through the quarter wave plate, such that the polarizations of the light generated from a light emitting point of the laser light source and the light reflected by the optical information storing medium and reentering the laser light source are orthogonal to each other so that a noise generated due to an interference by the light reflected by the optical information storing medium and reentering the laser light source is reduced; and a photodetector spaced apart from the optical path changer and the quarter wave plate, which receives the incident light reflected by the optical information storing medium and sequentially passing through the objective lens and the optical path changer and detects an information signal or an error signal.