Patent ID: 7120104

Claim:
An equalizer of an optical recording/reproducing apparatus comprising: a feedforward (FF) unit having a feedforward filter for removing pre-cursor from inter-symbol interference of an input signal and outputting a FF output signal; a feedback (FB) unit having a feedback filter for predicting post-cursor of the inter-symbol interference and outputting a result of the prediction in a FB output signal; a first adder and a second adder, each for adding the output signal from the FF unit and the output signal from the FB unit, to remove the inter-symbol interference, and respectively outputting a first output signal and a second output signal; a slicer for deciding a level of the first output signal from the first adder to be a predetermined level and feeding back a predetermined level signal to the FB unit; and a signal detection unit for outputting the second output signal having the inter-symbol interference removed by the second adder as a predetermined signal, using at least one of a trellis structure method and a tree structure method.