Patent ID: 7903361

Claim:
A method of detecting scratch defect in circumferential direction in a magnetic disk certifier which includes a write head and a read head and detects defects of a magnetic disk by writing test data through the write head while scanning the magnetic disk and by reading the test data through the read head, and which performs the following steps: through inspection of the magnetic disk defect data and the positions thereof on the magnetic disk are sampled, an inspection area for the sampled defect data is set which has a predetermined width in the radial direction of the magnetic disk and a length round the circle of the magnetic disk in the circumferential direction thereof or a predetermined length in the circumferential direction thereof, through setting a rectangular search frame for the defect data in the inspection area which has a certain width shorter than the predetermined width for the inspection area and a certain length shorter than the predetermined length in perpendicular direction with respect to the width, continuing defects are detected in which a plurality of defects continue in series in a region of the search frame, the search frame is successively shifted according to the continuing direction of the detected continuing defects so that the detected continuing defects are located in the region of the search frame so long as the detected continuing defects continue in the inspection area, and through detecting length or defect number of the detected continuing defects in the entire regions of the search frame before and after the shifting, the continuing defects having a length or a defect number more than a predetermined value is detected as a scratch defect in circumferential direction in the inspection area.