OPTICAL DISK DISCRIMINATING CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide an optical disk discriminating circuit which can improve the stability of a detecting operation of a peak of a photo-detecting signal (pulse signal) and which can also improve the stability of an optical disk discriminating operation. SOLUTION: When the kind of an optical disk is discriminated by a depth of a data recording layer from the surface which is irradiated with a light beam, the irradiation is performed while a focus position of the light beam is varied with a constant velocity in a direction of the depth from the surface of the optical disk. A bottom level of the photo-detecting signal according to the intensity of the reflected light is clamped at a prescribed level by a bottom level clamp circuit 43. The photo-detecting signal whose bottom level is clamped is compared with a prescribed reference voltage Vref at a comparator 45, and the peak of the photo-detecting signal (pulse signal) is detected according to the comparison result. The kind of the optical disk is discriminated by measuring the difference of the detection time of the peak (pulse signal).