| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical head, an optical disk unit, and its driving method, which prevent electric offset of a generated error signal without gain switching with respect to several kinds of optical disks different by standards. SOLUTION: The optical head is provided at least a semiconductor laser 1, an incidence optical system which leads an emitted luminous flux to an optical disk 7, a polarizing beam splitter 3 which separates a reflected luminous flux of the optical disk, a liquid crystal element 11 which changes the direction of polarization of the separated reflected luminous flux, a polarizing beam splitter 12 which changes the transmission quantity in accordance with the direction of polarization, and a photodetector, and the voltage of the liquid crystal element is turned on and off to switch the direction of polarization of the emitted luminous flux of the liquid crystal element, and a ratio of the quantity of light transmitted through the polarizing beam splitter is switched between optical disk reproducing operation and recording operation to suppress the offset of the generated error signal without gain switching of an electric circuit with respect to plural kinds of optical disks. |
