Γ-Profilometry on Rough Surfaces

We demonstrate first experimental results of Γ-profilometry on rough surfaces. Γ-profilometry is a new technique for measuring the shape of technical surfaces, which is based on spatio-temporal sampling of the coherence function. The main benefit of this approach is the combination of a low measurement uncertainty with a common path architecture. This makes it insensitive to mechanical distortions and flexible in handling because no external reference wave needs to be adjusted. Compared to Fizeau interferometry and white light interferometry, it only requires limited spatial coherence, which allows the use of eye-safe light sources, such as LEDs. Since the principle is based on sampling of the coherence function (Γ-function), we refer to this method as Γ-profilometry. So far, Γ-Profilometry was demonstrated on specular surfaces with measurement uncertainties in the nanometer regime over a range of several tenths of micrometers. Here, we show that the method also works on rough surfaces. We investigate the shape of a step-height normal with 1 µm steps and surface roughness of Sa=0.5 µm and find very good agreement with results obtained from a laser scanning confocal microscope.