| 摘要 |
PURPOSE:To adjust a focus position so that the detection sensitivity of either tracking or RF signal is optimized preferentially by increasing the detection sensitivity of a tracking error signal according to the decrease in the amplitude level of the RF signal. CONSTITUTION:The output terminal of an RF signal generating circuit 19 is connected to the input terminal of an envelope detecting circuit 25. This detecting circuit 25 detects variation in the amplitude level of an input signal, i.e. envelope signal to generate and output a correcting voltage V4 corresponding to the envelope signal, and the output terminal of this envelope detecting circuit 25 is connected to the output terminal of a focus adjusting circuit 23 through a resistance R2. Thus, the detection sensitivity of the tracking error signal is increased and the focus position of a light beam is adjusted so that the detection sensitivity of either tracking or RF signal is optimized preferentially. |
