Patent ID: 8208356

Claim:
An apparatus for optically checking defects in magnetic disks, comprising: a table device capable of holding a magnetic disk to be checked and rotating and shifting the disk; an illuminating device that irradiates a surface of the magnetic disk held by the table device with a laser beam; a specular reflection detecting device that detects a specular reflection out of reflected beams from the surface of the magnetic disk irradiated with a laser beam by the illuminating device; a scattered light detecting device that detects scattered light out of reflected beams from the surface of the magnetic disk irradiated with a laser beam by the illuminating device; a processing device that processes detection signals obtained by detection of the specular reflection by the specular reflection detecting optical device and detection signals obtained by detection of the scattered beams by the scattered beam detecting optical device to extract any defect on the magnetic disk; an output device that outputs results of processing by the processing device; and a control device that controls the table device, the illuminating device, the specular reflection detecting device, the scattered light detecting device and the processing device, wherein the specular reflection detecting device has a detector having a detecting face on which a plurality of pixels are arrayed, the control device, when causing the magnetic disk to make one turn by controlling the table device, consecutively shifts the magnetic disk in a radial direction so as to make a checkup area of the magnetic disk to be detected by the detector of the detecting device adjoin in the radial direction the checkup area of one turn before, and the processing device figures out the position of each defect by using, in addition to an output signal from each of the pixels having detected the specular reflection from the checkup area of the magnetic disk, also the output signals of some pixels out of the plurality of pixels having detected a specular reflection from the checkup area of one turn before and the checkup area of one turn after, both adjoining in the radial direction, and determines the type of the defect.