| 摘要 |
An optical pickup device has a near-field optical system having a numerical aperture of NA>1; a first light source emitting a first light having a first wavelength; a second light source emitting a second light having a second wavelength; an optical system multiplexing the first light and second light and irradiating the multiplexed light onto an optical recording medium having at least two recording layers; a first photodetector detecting the first light returned from the recording medium a second photodetector detecting the second light returned from the recording medium; a controller obtaining a signal corresponding to distance between the near-field optical system and the recording medium based on the returned second light, and obtaining a reproducing signal and a tracking signal of the recording medium and a focus signal corresponding to the recording layer based on the returned first light; and a focus position adjustment mechanism moving a focus position of the first light under control of the focus signal.
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