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Measuring Disk Windrows

IP.com Disclosure Number: IPCOM000039563D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Rabedeau, ME: AUTHOR

Abstract

Windrows on magnetic disks are measured by utilizing the fact that windrows diffract laser light into a characteristic pattern. Windrows are relatively long, narrow cracks in the magnetic coating of particulate data storage disks. As shown in Fig. 1, the areas on the screen labeled clouds of laser light are long, narrow nebulous areas of faint illumination. Outside of these areas, which are situated radially with respect to the disk and with respect to the point at which the laser beam intercepts the disk, the illumination due to non- windrow scattering from the disk is of lower intensity. The apparatus shown in Fig. 2 capitalized on the distinctive diffraction pattern exhibited by disks that are afflicted with windrows.

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Measuring Disk Windrows

Windrows on magnetic disks are measured by utilizing the fact that windrows diffract laser light into a characteristic pattern. Windrows are relatively long, narrow cracks in the magnetic coating of particulate data storage disks. As shown in Fig. 1, the areas on the screen labeled clouds of laser light are long, narrow nebulous areas of faint illumination. Outside of these areas, which are situated radially with respect to the disk and with respect to the point at which the laser beam intercepts the disk, the illumination due to non- windrow scattering from the disk is of lower intensity. The apparatus shown in Fig. 2 capitalized on the distinctive diffraction pattern exhibited by disks that are afflicted with windrows. Two detectors, A and B, are located radially and circumferentially, respectively, relative to the point at which the laser beam intercepts the disk. The A detector is illuminated by the windrow light, while the B detector is illuminated by light that is scattered by disk features other than windrows. The output of the instrument is approximately proportional to the percent of disk surface area that is covered by windrows.

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