| 摘要 |
PURPOSE:To eliminate noise components without requiring any adjustment even in case of the variance of circumstance, dirt of an optical system, or the like by controlling the gain of a variable gain amplifier so that the input signal average value of a differential amplifier is equalized in a photomagnetic reproducing device using the differential method. CONSTITUTION:The light emitted from a semiconductor laser 14 is made incident on a photomagnetic recording medium 1 by an optical system 18, and the reproduced light is inputted to a differential amplifier 25 through photoelectric converting means 19 and 20 from the optical system 18. Meanwhile, outputs of photoelectric converting means are inputted to a differential amplifier 33 through LPFs 31 and 32, and the difference (DC component) between average values of two input signals is detected, and an error detecting circuit 37 is smoothed by an integrator 36 and is converted to a DC voltage, and this voltage is supplied as an AGC signal to a variable gain amplifier 24 of the photoelectric converting means 20 to equalize two input signal levels of the differential amplifier 25. Consequently, a reproduced signal from which noise components are eliminated is outputted from the differential amplifier 25. |
