| 摘要 |
PURPOSE:To detect correctly a negative feedback area even when the disk is different by composing so that a slice level to detect a negative feedback area can automatically keep up with the change of a signal level due to a reflecting ratio of the disk and a variance of a modulation factor. CONSTITUTION:By adding an output of peak level detectors 3 and 4, namely, levels M and N with an adder 17 of resistances 36 and 37, a slice level is made, this is impressed to a positive input of a comparator 5, on the other hand, an output of a peak level detecting device 2, namely, R is inputted to a negative input,and only when the level of an envelope R is lower than the slice level P, a high level is outputted to the output of the comparator, and a waveform (c) can be obtained. For the output of spots B and C for the servo a tracking error signal (b) is obtained through photoelectric converting devices 6 and 7, and a differential amplifier 8. Here, by signals (b) and (c), when the signal (c) is a high level, a negative feedback area of a tracking error signal (b) can be detected. Thus, since the slice level to detect the negative feedback area automatically follows even when the disk is different, the negative feedback area can be correctly detected. |
