Apparatus for reproducing information recorded on recording medium while adjusting middle level of detected signal corresponding to the information

An apparatus for reproducing information from a recording disk by emitting a light beam onto a recording track formed on the recording disk, the information including at least first information to be reproduced and second information for controlling the reproduction of the first information, the first information being recorded on the recording track, the second information being recorded on a recording area formed on the recording disk, the recording area being located a predetermined distance out of a location of the recording track in a radial direction of the recording disk, the apparatus comprising:

• a light emitting device that emits the light beam onto the recording track and the recording area;
• a light beam detecting device that detects the light beam reflected from the recording track and the recording area, and generates detection signals;
• a sampling device that samples each of the generated detection signals;
• a level adjustment signal generating device that determines the type of the sampled detection signal based on the place from which the detected light beam is reflected, generates a level adjustment signal based on the middle level corresponding to the determined signal type, and subtracts the level adjustment signal from the sampled detection signal to produce a compensated detection signal;
• and
• a decoding device that decodes the compensated detection signal to reproduce the information,
• wherein said level adjustment signal generating device comprises:
• a middle level detection circuit that detects a minimum middle level signal when the polarity of a sampling value included in the compensated detection signal with respect to the middle level reverses between adjacent sampling values, and outputs the detected signal as a middle level sampling signal;
• an average calculating circuit for calculating averages of the middle level sampling signals supplied thereto from the middle level detection circuit and outputting average middle level signal;
• shift signal generating circuitry that generates a middle level shift signal based on the middle level corresponding to the determined signal type;
• and
• an adding device that adds the generated middle level shift signal to the average middle level signals.

An information reproducing apparatus comprising:

• a signal reader for reading signals from a recording medium, wherein the signals read from the recording medium include signals of different types each of which has a different middle level;
• an A/D converter for sampling the signals of different types read from the recording medium;
• a decoding circuit for reproducing information corresponding to the sampled signals;
• and
• middle level adjustment circuitry for adjusting the middle levels of the signals output by the A/D converter so that the middle levels of the sampled signals of different types are uniform, the middle level adjustment circuitry comprising level adjustment signal generating circuitry for generating level adjustment signals having levels that change in accordance with the signal type of the sampled signals, and signal combining circuitry for combining the level adjustment signals with the sampled signals output by the A/D converter and outputting the level-adjusted sampled signals to the decoding circuit,
• wherein the level adjustment signal generating circuitry comprises:
• a middle level detection circuit supplied with level-adjusted sampled signals for generating middle level sampling signals in response thereto;
• an average calculating circuit for calculating averages of the middle level sampling signals supplied thereto from the middle level detection circuit, and outputting average middle level signals;
• a shift signal generating circuit for generating respective shift signals for shifting the middle levels of a corresponding signal type to a common middle level;
• a selecting circuit for selecting the shift signals in accordance with the signal type of the signals read from the recording medium, and outputting the selected shift signals;
• and
• a first signal combining circuit for combining the selected shift signals output by the selecting circuit and the average middle level signals output by the average calculating circuit, and outputting the combined signals as the level adjustment signals.