Patent ID: 7599272
Filing Date: 2009-10-06
Classification: G11B

Abstract:
1. A multi-level information method of recording or reproducing multi-level information by virtually setting cells at constant intervals on a track of an optical information medium wherein information is recorded or reproduced with a light spot and by varying an information pit width in a direction of the track or an information pit area, comprising the steps of: detecting a reproduced signal by radiating a light spot onto the track; detecting a cell border value by sampling the reproduced signal when the center of the light spot falls on a border between one cell and its following cell; judging multi-level information of the following cell based on the cell border value; and detecting a cell center value by sampling the reproduced signal when the center of the light spot falls on the center of a cell, wherein, in the judging step, multi-level information of a cell is judged based on both of the cell border value and the cell center value; wherein, in the judging step, a candidate value based on the cell border value and a candidate value based on the cell center value are determined to judge final multi-level information from a plurality of candidate values; and wherein, in the judging step, when a first candidate value obtained from the cell center value is given as “a” a second candidate value is given as “b”, and a third candidate value obtained from the cell border value is given as “x” in the judging step if “a”=x, “a” is judged as multi-level information of the following cell if “a”=“x”.