Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1979-06-29
1982-06-15
Corbin, John K.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356446, G01B 1130, G01N 2147
Patent
active
043347800
ABSTRACT:
An optical method and apparatus for noncontacting inspection of a specimen to evaluate quantitatively its surface roughness characteristics are disclosed.
The distribution of light scattered by a Gaussian rough surface illuminated with a laser beam is obtained with a transform and cylinder lens pair (for a one-dimensional light distribution), or by a transform lens alone (for a two-dimensional Gaussian light distribution) when no tooling marks, scratches, etc., would mar the surface and mask the measurement. Spatial frequency halfwidths of the optical Fourier transform spectrum of the scattered light are known to be linearly related to the planar surface roughness characteristics. Hence, with appropriate calibration, the measured light distribution halfwidths can be used to evaluate surface roughness. Measurements are not restricted to planar surfaces; curved specimen shapes can be employed with appropriate optical adjustments. Beam forming components can also be used to achieve similar surface roughness measurements on curved shapes, such as a conical mirror for use with cylindrical or tapered holes.
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Arnold Bruce Y.
Corbin John K.
Grumman Aerospace Corporation
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