Phase Metrics, Inc.

George A Burt, Jr

Peter C Jann

Igor Iosilevsky

Joel M Libove

Kenneth H Womack

Wayne W Li

Vladimir Pogrebinsky

Vlastimil Cejna

David Ferry

A simple yet versatile non-contact optical inspection instrument and method are described for measuring the height and width of defects and contaminants on a magnetic disk surface. The instrument includes a sensor which produces an illumination beam that is modulated and then focused normally on the disk surface as a spot. The illumination spot is Doppler shifted due to the movement of the disk and the diffusely reflected light is interfered with a reference beam produced by the sensor's illumination optics. The sensor uses two collection optics channels which simultaneously detect both the specular reflected light and the diffuse scattered light produced by the disk surface. The phase shift of the specular reflected light and that of the diffusely scattered light are measured. The output signals from the sensors are processed to estimate the size and type of the defects. Another aspect of the present invention includes a demodulator which increases the frequency of an FM signal. Pulses representing the zero-crossings of the signal are generated and filtered to provide a voltage that is proportional to the frequency of the FM signal. Because the pulse train has a frequency that is significantly greater than the input frequency, a low-pass filter with both a high cut-off frequency and a gradual roll-off in frequency response may thus be used to optimize the output or demodulated signal in terms of increased bandwidth or faster response and more linear group delay.

Method and apparatus for detecting defects on a disk using

A simple yet versatile noncontact optical inspection instrument and method are described for the inspection of magnetic disk surfaces for surface defects. This instrument is capable of inspecting the disk surface at any point in the disk manufacturing process. Surface defects such as bumps, pits and scratches can be measured. Surface contaminants such as particles and stains can also be measured. The instrument is also capable of discriminating between surface defects and surface contaminants. The instrument is comprised of two identical optical sensors which are located on opposite sides of the disk. A carriage supports and translates these sensors along the disk radius while a spindle rotates the disk. Both surfaces of the disk are therefore simultaneously scanned in a spiral fashion. The sensor's illumination optics produce a monochromatic focused spot of light which is normally incident upon the disk surface. The sensor uses two collection optics channels which simultaneously detect both the specular reflected light and the diffuse scattered light produced by the disk surface. Both the angle and power of the specular reflected light are measured, while just the power of the diffuse scattered light is measured. The output signals from the sensors are processed to estimate the size of the defects and to determine the type of defect.

Apparatus and method for surface inspection by specular interferometric

A method and apparatus for detecting defects on the surface of a data recording medium. In one embodiment the present invention includes a sensor for detecting defects on the surface of a magnetic disk. The sensor generates an analog voltage signal that is representative of a surface anomaly detected on the disk surface. An analog signal processor processes the signal before it is received by a peak detecting circuit. The peak detecting circuit detects and converts a peak of the analog signal into digital data. The digital data is received and manipulated by a digital signal processor where the peak amplitude, average peak amplitude and average peak power of the defect may be calculated.

Method and apparatus for combined glide and defect analysis

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Fremont, CA, United States of America

George A Burt, Jr