| 摘要 |
PURPOSE:To attain highly accurate control by using a signal being the result of sampling and detecting a regenerative signal outputted from a differential amplifier when an area with a magneto-optical information signal not recorded thereupon is reproduced as a signal used for automatic control. CONSTITUTION:A luminous flux 2 from a semiconductor laser 1 is led onto an information track of a magneto-optical disk 7 having a data area pinched by a servo area not having a magnetic domain and a servo area. A reproduced luminous flux 9 is separated into the S polarized light component 12 and the P polarized light component 13 by a polarized light beam splitter 11 and they are led to photoelectric conversion elements 14, 15. They are converted into voltage signals 18, 22 and inputted to a fixed again circuit 19 and a variable gain circuit 23. Signals 24, 25 are inputted to a subtraction circuit 27 being a differential amplifier, from which a sum signal 28 and a difference signal 29 are outputted. The signal 29 is inputted to a gain control signal generating circuit 33, from which a gain control signal 34 is generated. The signal 34 is inputted to the circuit 23, which operates to make the gain of the signals 25, 24 equal to each other. Since the difference signal is detected from the servo area whose magnetizing state is always constant, the control is surely operated without being affected by the recording state of the information signal. |
