METHOD FOR DETECTING DEFECT OF MEDIUM IN MAGNETIC RECORDING MEDIUM

摘要

PURPOSE:To attain highly accurate detection of defect by detecting a noise pulse existing in the vicinity of a reproduced signal pulse of a recording medium subject to magnetization processing including DC erasure of unsaturated type. CONSTITUTION:A head 61 and a recording/erasure circuit 62 impresses a DC magnetic field sufficient larger than the coercive force of a magnetic disk medium 60 its recording direction and to measure the average level of the reproduced output by a means level measuring instrument 64 at the first stage. A DC magnetic field smaller than the saturation magnetic field of the medium 60 is impressed at the succeeding 2nd stage to impress unsaturated DC erasure, the noise mean level is measured and compared with the 1st stage measured value to apply the unsaturated DC erasure while varying the erasure magnetic field so that the noise mean level measured value is maximized. Since the noise pulse having a prescribed ratio or over is detected by the pulse noise detection circuit 65 with respect to the measured noise mean level in the 1st state corresponding to the defect in existence near the reproduced signal pulse of the medium 60 in this state, the detect of the magnetic recording medium is detected with high accuracy.