Optical disc device and optical disc playback method

Abstract

According to one embodiment, a device includes a filter which limits a frequency bandwidth of a reproduced signal from an optical disc, an AD conversion module which converts an output signal from the filter into a multilevel digital signal, an equalizing module for equalizing a waveform of the multilevel digital signal based on a predetermined partial response class and generating an equalizing playback signal, a detection module for generating binary data corresponding to data recorded on the optical disc based on the equalizing playback signal, a module for determining an amplitude value of each of an input signal to and an output signal from the equalizing module with respect to each binary data sequence output from the detection module, and a module for adjusting a high-frequency amplification amount of the filter such that an amplitude value before waveform equalization and an amplitude value after waveform equalization satisfy a predetermined relationship.

1 . An optical disc device configured to play back an optical disc comprising data recorded by Partial Response Maximum Likelihood (PRML) method, 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 detection module configured to generate binary data corresponding to the recorded data on the optical disc based on the equalized playback signal;   an amplitude value extraction module configured to determine an amplitude value of an input signal and an amplitude value of an output signal from the adaptive equalizer with respect to a code length of a sequence of the binary data from the maximum likelihood detection module; and   a filter configured to adjusting an amplification amount in a high-frequency region of the analog filter in such a manner that the amplitude value of the input signal to the adaptive equalizer of the code length of the binary data sequence and the amplitude value of the output signal from the adaptive equalizer of the code length binary data sequence satisfy a predetermined relationship.   
   
   
       2 . The optical disc device of  claim 1 , wherein the amplitude value extraction module comprises:
 a delay module configured to accept an input signal to the adaptive equalizer as an input signal;   a switch configured to switch between an output signal from the adaptive equalizer and an output signal from the delay module;   a buffer 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 using a unit length of the code length as a clock cycle;   a code length detection module 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 detection module; and   a selection module configured to select an amplitude value of the equalized playback signal from the data holder based on the selection signal at a sampling point corresponding to the center of the detected code length.   
   
   
       3 . The optical disc device of  claim 2 , further comprising an average value calculator configured to calculate an average of two amplitude values sampled at two sampling points of either a corresponding output signal from the adaptive equalizer or an output signal from the delay module. 
   
   
       4 . The optical disc device as in any one of  claims 1 - 3 , wherein the filter comprises a sub module configured to adjust the high-frequency amplification amount of the analog filter in such a manner that amplitude values of signals of a plurality of code lengths satisfy a predetermined relationship. 
   
   
       5 . The optical disc drive as in any one of  claims 1 - 3 , wherein the filter is configured to adjust the amplification amount in the high-frequency region of the analog filter in such a manner that a ratio between the amplitude value of the input signal to the adaptive equalizer and the amplitude value of the output signal from the adaptive equalizer is substantially equal to a predetermined value. 
   
   
       6 . An optical disc playback method of Partial Response Maximum Likelihood (PRML), comprising:
 setting a transfer characteristic of an analog filter to a predetermined value;   playing a playback signal from the optical disc and determining an amplitude value before adaptive equalization;   playing a playback signal from the optical disc and determining an amplitude value after adaptive equalization;   determining whether amplitude values of a pattern before and after adaptive equalization satisfy a predetermined relationship; and   adjusting an amplification amount in a high-frequency region of the analog filter when the amplitude values of the pattern before and after adaptive equalization fail to satisfy the predetermined relationship.   
   
   
       7 . The optical disc playback method of  claim 6 , further comprising
 determining amplitude values of patterns of a plurality of code lengths of a playback signal before adaptive equalization in the determining the amplitude value before adaptive equalization,   determining amplitude values of patterns of a plurality of code lengths of a playback signal after adaptive equalization in the determining of the amplitude value after adaptive equalization, and   pattern-by-pattern adjusting of an amplification amount in a high-frequency region of the analog filter in such a manner that amplitude values of a signal of a plurality of patterns before and after adaptive equalization satisfy a predetermined relationship.   
   
   
       8 . The optical disc playback method as in any one of  claims 6  and  7 , further comprising:
 adjusting an amplification amount in a high-frequency region of the analog filter in such a manner that a ratio between an amplification amount of an input signal to the adaptive equalizer and an amplitude value of an output signal from the adaptive equalizer is substantially equal to a predetermined value.