Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1998-06-26
1999-11-02
Font, Frank G.
Optics: measuring and testing
By polarized light examination
With light attenuation
356237, 356371, 356426, 250572, G01B 1124, G01B 1130, G01N 2100, G01N 2188
Patent
active
059780916
ABSTRACT:
An apparatus for measuring the height and diameter of laser-zone texture bumps on a rigid magnetic disk substrate is disclosed. The apparatus has a disk holder for supporting and rotating the substrate, and an optical beam-source assembly for directing a focused laser beam on the substrate, and for shifting the position of the beam's illumination spot on the substrate in a tracking (radial) direction. An optical detection assembly in the apparatus measures the deflection of the laser beam due to specular reflection of the beam by laser-zone texture bumps, as a function of time, in both scanning (circumferential) and tracking directions. A computational device in the apparatus functions to (i) calculate scanning and tracking deflection values which characterize beam deflections in the scanning and tracking directions, respectively, for a texture bump passing through the illumination spot produced by the beam on the substrate, (ii) select for bump-height analysis, those texture bumps whose scanning deflection values are above a selected threshold value and whose tracking deflection values are below a selected threshold value, indicative of a condition in which the selected textured bumps are each in focus and centered within said illumination spot, and (iii) determine the texture bump heights and diameters of the selected bumps from the beam deflections in the scanning direction. Also disclosed is a method by which the apparatus measures the light power which is scattered by the of laser-zone texture bumps on a rigid magnetic disk substrate.
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Jann Peter C.
Krumbuegel Marco A.
Lee Reginald
Yang Ming M.
Dehlinger Peter J.
Font Frank G.
Frazier Jeffery D.
HMT Technology Corporation
Punnoose Roy M.
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