Patent ID: 6552988
Filing Date: 2003-04-22
Classification: G11B

Abstract:
An apparatus for generating a plurality of types of detection signals corresponding to information recorded on a recording medium by detecting a light beam reflected from the recording medium, and for reproducing the information by decoding the detection signals, the detection signals each having a different middle level corresponding to its signal type, the apparatus comprising:a light emitting device that emits the light beam to the recording medium; a light beam detecting device that detects the light beam reflected from the recording medium, and that generates the 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, generates a level adjustment signal based on the middle level that corresponds to the determined signal type, and subtracts the level adjustment signal from the sampled detection signal to produce a compensated detection signal; 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 signals; 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.