In an interferometer which uses a reference surface, the measured surface heights
correspond to the difference between the test and reference surfaces. To
accurately determine the rms roughness of supersmooth surfaces, the effects of
the reference surface roughness need to be removed. One technique for doing this
involves averaging a number of uncorrelated measurements of a mirror to generate
a reference surface profile which can then be subtracted from subsequent
measurements so that they do not contain errors due to the reference surface.
The other technique provides an accurate rms roughness of the surface by taking
two uncorrelated measurements of the surface. These two techniques for
measurement of supersmooth surfaces are described in detail, and results of the
measurement of a 0.7-Å rms roughness mirror are presented. The expected
error in the rms roughness measurement of a supersmooth mirror due to instrument
noise is 0.02 Å.
© 1990 Optical Society of America
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