Fast Coherence Scanning Interferometry for Measuring Smooth, Rough and Spherical Surfaces

Coherence scanning interferometry is a useful instrument for measuring the geometry of a wide range of surfaces with high resolution. By introducing two objectives with a high numerical aperture in both arms of a Michelson interferometer it is possible to investigate spherical and aspherical surfaces. In addition to classical interferometry, the method can be applied to smooth, rough or separated surfaces. We describe a system providing fast and accurate results using a high-speed charge-coupled device camera. Thus the acquisition lime for a 124 X 128 X 8 bit image can be reduced to less than 1.5 s for a 100 mu m z range. By using a light source with a low temporal coherency, it is possible to perform optical sectioning. The full width at half-maximum of the envelope signal is about 10 mu m.