| 摘要 |
PURPOSE:To improve the detecting ability for a defect part of an magneto- optical recording medium by providing a summing amplifier which detects the sum signal of information signals from 1st and 2nd photodetectors and an amplitude detecting circuit which detects the output signal of the summing amplifier exceeding a preset reference comparative amplitude value. CONSTITUTION:A recording signal from a magneto-optical recording medium 6 is read with laser light and inputted to photodetectors 11 and 11, and they are converted into electric signals, which are inputted to a differential amplifier 12 and the summing amplifier 18. Signal components detected by the photodetectors 11 and 11' are opposite in phase to each other, so almost none of them appears at the output of the summing amplifier 18. When a defect part which causes variation in reflection factor is reproduced, on the other hand, the signals detected by the photodetectors 11 and 11' are in phase with each other, so they are amplified by the summing amplifier 18 and outputted. When this exceeds the reference comparative amplitude value, a high level signal is outputted by a comparator 19 and inputted as a defect detection signal to a defect correcting circuit to correct the defect noise of a playback video signal.
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