Patent ID: 8576680

Claim:
A circuit for generating a signal for controlling reproduction of data recorded on an optical disc, comprising: an amplifier to amplify an electric signal corresponding to an intensity of a reflected light from an optical disc; a first detection circuit to detect an upper envelope of an output signal from the amplifier, and to output an upper envelope signal; a second detection circuit to detect a lower envelope of an output signal from the amplifier, and to output a lower envelope signal; a first A/D converter to convert the upper envelope signal into a first digital signal; a second A/D converter to convert the lower envelope signal into a second digital signal; and a digital signal processing circuit to perform calculation processing of the first and the second digital signals, and to output a signal for controlling reproduction of data recorded on the optical disc, wherein the digital signal processing circuit is provided with: an inverter to reverse the polarity of the second digital signal, and to output a third digital signal; a first low pass filter to transmit a low-frequency component of the third digital signal; a first subtracter to subtract the output signal of the low pass filter from the third digital signal; and a polarity data extraction circuit to extract polarity data from the output signal of the first subtracter, and to output a track crossing detection signal as the signal for controlling reproduction.