OPTICAL DISK UNIT, VIDEO REPRODUCING DEVICE USING OPTICAL DISK UNIT, SERVER, CAR NAVIGATION SYSTEM, INTEGRATED CIRCUIT, AND RECORDING/REPRODUCING METHOD

摘要

An optical disk unit is provided with an optical head (1) comprising a light source (21), a condensing optical system including an objective lens (28) for receiving a light beam emitted from the light source and forming a minute spot on a multilayered optical recording medium, a photodetector (201) for receiving the light beam reflected by the multilayered optical recording medium and outputting an electrical signal according to the light intensity, and a coma aberration correcting element (26) for correcting the comma aberration of the condensing optical system, and a processing circuit (3) for controlling the condensing optical system and the coma aberration correcting element, wherein the processing circuit controls the condensing optical system and the coma aberration correcting element in such a manner that the correction of the coma aberration from a value suitable for a first recording layer to a predetermined value specified with respect to a second recording layer is started before the movement of the focal position of the minute spot from the first recording layer to the second recording layer is completed.