The “spectral radar” as an optical profiler

The “spectral radar” is a white light interferometer working in the Fourier domain [1]. This measuring principle is now commonly used for oct (optical coherence tomography), since it needs no depth scan, and has a strong signal-to noise-advantage over scanning white light interferometry. It turns out that there is another quite important advantage, compared to full field white light interferometry on rough surfaces: we are much less limited to spatial coherence conditions. We make use of these advantages for an optical profiler. The measurement uncertainty is better than 1µm, at optically smooth surfaces, and equal to the roughness, at optically rough surfaces. Compared to triangulation principles, the measuring uncertainty is independent from the aperture. Thus the working distance can be very big. The data rate is bigger than 10.000 pixels/sec. [1] G. Häusler, J. M. Herrmann, V. Höfer, M. W. Lindner, P. Pavlicek u. Ringler, Proc. of EOS Top. Meet. „Free Space Micro-Optical Systems“, Engelberg (1996) 48-49