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Optic Electrical Measuring of Surface Planeness

IP.com Disclosure Number: IPCOM000091431D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Wolf, H: AUTHOR [+2]

Abstract

Surface 0 of an uncoated or coated rotating magnetic disk has height variations Delta h caused by irregularities of the surface. Variations Delta h are measured by radially scanning the surface 0 by a light beam having a thin but broad cross-section which is parallel to the surface. The light beam is produced by a light section microscope, made by Zeiss-West Germany, a slit diaphragm B, and is projected onto surface 0 at an angle of 45 Degrees and is again reflected by such surface at an angle of 45 Degrees. If the height of the scanned surface is changed, e.g., by the amount of Delta h to 0', the reflected light beam is shifted in parallel direction as shown by the dotted line. The reflected light beam then enters not the microscope ocular directly, but an additional measuring device via two parallel mirrors S1. and S2.

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Optic Electrical Measuring of Surface Planeness

Surface 0 of an uncoated or coated rotating magnetic disk has height variations Delta h caused by irregularities of the surface. Variations Delta h are measured by radially scanning the surface 0 by a light beam having a thin but broad cross-section which is parallel to the surface. The light beam is produced by a light section microscope, made by Zeiss-West Germany, a slit diaphragm B, and is projected onto surface 0 at an angle of 45 Degrees and is again reflected by such surface at an angle of 45 Degrees. If the height of the scanned surface is changed, e.g., by the amount of Delta h to 0', the reflected light beam is shifted in parallel direction as shown by the dotted line. The reflected light beam then enters not the microscope ocular directly, but an additional measuring device via two parallel mirrors S1. and S2.

The additional measuring device is one-part only and consists of opaque mirror S1, triangular diaphragm B1' or a wedge-shaped filter B1, ground-glass plate M1, a lens and a photomultiplier P1. The parallel shift of the reflected light beam of constant width and thickness is converted, by B1' or B1, into a proportional changing of the light intensity and this intensity is again converted by P1, into a corresponding voltage change. The latter is proportional to the changing height of surface 0. This change of the light intensity of the light beam upon its parallel shifting is caused by B1' with variable aperture width, by changing the width of the light beam, or by gray wedge B1 of constant width but wedge-like changing thickness by changing the light absorption. B1 has the advantage that nonuniform brightness of the light beam due to non-uniform illumination of B does not have the conseque...