| 摘要 |
PURPOSE:To demodulate stably a data irrespective of the fluctuation of an envelope at all by providing the first and the second differentiators, an ampli tude detector, a zero point detector and a demodulator. CONSTITUTION:A read-out signal (c) which is read out by an optical head 2 is amplified by an amplifier 3, differentiated by the first differentiator 4, and a differential signal (e) is obtained. A 2nd order differential signal (h) which has been obtained by differentiating further the differential signal (e) by the second differentiator 6 is inputted to a zero point detector 7 and compared with a voltage of zero volt, and converted to a binary-coding signal (j) which becomes '1' and '0', in case of + side and - side, respectively. The differential signal (e) is compared with a threshold voltage + or -vt by an amplitude detector 5, a binary-coding signal (f) which becomes '1' and '0', in case of + side from +vt, and - side, respectively, and a binary-coding signal (g) which becomes '1' and '0', in case of - side from -vt, and + side, respectively are obtained, and by using these signals together with said binary-coding signal (j), a data (m) is demodulated by a demodulator 8. The operation related to this demodulation is all executed by a differential system, therefore, it has no relation at all to the fluctuation of an envelope of the read-out signal (c).
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