| 摘要 |
PURPOSE:To always put surely the brake by adding a signal obtained by envelope detection of a reproduced information signal and the output signal of an LPF of the reproduced information signal so that one signal having a higher level is taken out selectively as the output and using this output as a signal indicating the position of an optical beam to a track. CONSTITUTION:A waveform detecting circuit 50 consists of an envelope detecting circuit 51, a low-pass filter 52, and an adding circuit which adds an output signal RE of the envelope detecting circuit 51 and an output signal RL of the low-pass filter 52 so that one signal having a higher level is taken out selectively as the output. In this adding circuit, collectors and emitters of two transistors TRs 54 and 55 are connected commonly respectively, and these commonly connected emitters are connected to a resistance 56, and the signal RE is supplied to the base of TR54, and the signal RL is supplied to the base of the TR55, and the output is taken out from commonly connected emitters. An output signal RT of the waveform detecting circuit 50 and a tracking error signal TE are supplied to a signal generating circuit 60 to generate a pulse signal BP for brake. |
