| 摘要 |
A method and apparatus for measuring the physical characteristics of reflective or transparent surfaces may be used to detect particulates, measure surface roughness, and reconstruct surface images and detect defects in regular patterns on both smooth and rough surfaces. The method is based on, and takes advantage of, the fact that high frequency spatial Fourier components are formed when a Gaussian profile beam interacts with an irregular, or otherwise inhomogeneous, surface. Through the measurement of these non-Gaussian components of the reflected beam, information about the sample surface may be obtained. An apparatus based on this principle comprises a light source [12] for producing a beam of light [10] directed along an optical path; a spatial filter [34], positioned along the optical path downstream from the light source, for giving the beam of light a Gaussian intensity profile [18]; positioning means [22] for positioning the material [20] in the optical path downstream from the spatial filter [34]; an inverse spatial filter [40], positioned along the optical path downstream from the material, for removing from the beam a Gaussian intensity profile; and a detector [46], positioned along the optical path downstream from the inverse spatial filter, for detecting the beam.
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