Patent ID: 8345524

Claim:
An information readout apparatus comprising: an offset corrector that performs a HPF (high-pass filter) operation that controls an offset of a readout signal so that a DC level of the readout signal assumes a zero amplitude reference, and a level-correction operation that controls an offset of the readout signal so that a DC level of a shortest period signal included in the readout signal assumes a zero amplitude reference, while switching therebetween; a maximum-likelihood detector that identifies binary data from the readout signal for which the offset is corrected by said offset corrector; a defect judgment unit that detects a disturbance of the readout signal based on a change of an envelope of the readout signal; and a gate-signal generator that generates a switching signal for switching operation of said offset corrector based on a detection result of the waveform disturbance by said defect judgment unit, wherein said offset corrector comprises: a subtractor that corrects an offset deviation from the readout signal; an error-signal generator that generates an error signal, which is used in said level-correction operation, based on an input data of said most-likelihood detector and the binary data detected by said most-likelihood detector; a selector that selects and delivers the output of said subtractor or said error signal depending on said switching signal; and an integrator that integrates the output signal of said selector, to feed back the integrated result to said subtractor.