Abstract: In a method and an apparatus for inspecting a surface of a disk, a disk that is a sample is rotated, and a light beam is applied to the sample while moving the sample in the direction perpendicular to the center axis of rotation. Light reflected and scattered from the sample in a first direction is detected to obtain a first detection signal while applying the light beam. Light reflected and scattered from the sample in a second direction is detected to obtain a second detection signal while applying the light beam. The first detection signal and the second detection signal are processed to detect a defect on the sample. A preset threshold is compared with the output level of the first detection signal or the output level of the second detection signal to determine whether the material of the disk that is the sample is a predetermined material.

Abstract: A magnetic disk certifier includes a defect detector circuit comprising a low-pass filter for extracting a low frequency component of the read-out signal, the low frequency component containing a signal component of the error, a signal generator circuit for generating a signal having a predetermined frequency lower than the frequency of the read-out signal, a synthesizer circuit for synthesizing an output signal of the low-pass filter and the signal outputted from the signal generator circuit and a comparator for generating an error signal by comparing the synthesized signal from the synthesizer circuit with a predetermined reference level.

Abstract: A magnetic disk certifier includes a defect detector circuit comprising a low-pass filter for extracting a low frequency component of the read-out signal, the low frequency component containing a signal component of the error, a signal generator circuit for generating a signal having a predetermined frequency lower than the frequency of the read-out signal, a synthesizer circuit for synthesizing an output signal of the low-pass filter and the signal outputted from the signal generator circuit and a comparator for generating an error signal by comparing the synthesized signal from the synthesizer circuit with a predetermined reference level.