Optical disc device and optical disc playback method

An optical disc device configured to play back an optical disc, comprising:

• an analog filter configured to limit a frequency bandwidth of a playback signal from the optical disc;
• an Analog-to-Digital (AD) converter configured to convert an output signal from the analog filter into a multilevel digital signal;
• an adaptive equalizer configured to equalize a waveform of the multilevel digital signal based on a predetermined partial response class and to generate an equalized playback signal;
• a maximum likelihood detector configured to generate binary data corresponding to the recorded data recorded on the optical disc based on the equalized playback signal;
• an amplitude value extractor configured to obtain an amplitude value of a signal selected from an input signal to the adaptive equalizer and an output signal from the adaptive equalizer with respect to each binary data sequence output of a code length from the maximum likelihood detector;
• and
• an adjuster configured to adjust an amount of high-frequency amplification of the analog filter such that the amplitude value of the input signal to the adaptive equalizer of each binary data sequence of code length and the amplitude value of the output signal from the adaptive equalizer of each binary data sequence of code length satisfy a predetermined relationship,
• wherein the amplitude value extractor comprises:
• a delay module to which an input signal to the adaptive equalizer is input;
• a switch configured to switch between an output signal from the adaptive equalizer and an output signal from the delay module;
• a data storage module configured to delay and hold either the output signal from the adaptive equalizer or the output signal from the delay module switched by the switch on a clock of a unit length of the code length;
• a code length detector configured to detect the code length by detecting a data change point of the binary data;
• a selection signal generator configured to determine a response length of the partial response signal based on the partial response class and to generate a selection signal from the determined response length and the code length detected by the code length detector;
• and
• a selector configured to select an amplitude value of the equalized playback signal of a sampling point corresponding to the center of the detected code length from the data storage module based on the selection signal.