Optical pickup device
Number of patents in Portfolio can not be more than 2000
United States of America Patent
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Apr 22, 2003
Grant Date -
N/A
app pub date -
Jun 13, 2000
filing date -
Jun 16, 1999
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A phase difference plate (12) converts states of polarization of emergent light form a laser light source (13) and return light form an optical recording medium (5). A diffractive element (21) separates the return light from an optical axis leading from the laser light source (13) to the optical recording medium (5), and guides the return light to a photodetector (14) on the basis of a difference between the states of polarization of the emergent light and the return light. The polarization direction of emergent light from the laser light source (13) is arranged so as to be oriented in the radial direction of the optical recording medium (5) (in the direction of birefringence of the optical recording medium). The azimuth and the amount of phase of the phase difference plate (12) are set so that a peak of a signal in tensity detected by the photodetector (14) appears while an amount of birefringence of the optical recording medium changes from 0 to a quarter wavelength of the laser light when the amount of birefringence of the optical recording medium (5) is changed.
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