Recent developments in surface contouring by means of speckle interferometry

In specific applications the electronic speckle pattern interferometry (ESPI) is superior to other optical surface metrology methods. The two-wavelength ESPI for surface contouring can achieve both high accuracy of height resolution in the micron range and short measurement times far below one second. A further advantage of this method is that, compared to e.g. triangulation, illumination axis and observation axis can be identical. The main problems of interferometric methods in general are on one hand the enormous sensitivity against disturbances caused by environmental movements and vibrations. On the other hand discontinuous object surfaces cause phase ambiguities leading to uncertainties in surface reconstruction. This article presents new concepts for tackling these problems via simultaneous data acquisition and multi-wave length evaluation respectively. Furthermore a vibration stable set-up concept, a hardware based interferogram evaluation, a special solution for a loss less sequential superposition of several spatially separated laser beams and a concept of a fast stability control for diode lasers are introduced.