| 摘要 |
PURPOSE:To prevent the deterioration in performance due to temperature changes or secular changes by splitting reflected or regenerated light from a magneto-optical medium into two optical paths, converting its current difference directly to eliminate in-phase noise components. CONSTITUTION:A regenerated information signal from a magneto-optical medium is split into two optical paths depending on the difference from the polarized face and the amplification factor of an avalanche photodiode 32 is adjusted by a reverse bias voltage control circuit 35 to make two DC components equal to each other thereby eliminating the in-phase noise components. Since the differential amplifier 12 is constituted to extract the output in response to the difference of the DC component, automatic control for bringing the output of differential amplifier 12 to zero is attained.
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