Optical 3D testing of micro structures

Optical measuring techniques for micro structures are limited by the numerical aperture of the objective. Within these limits different techniques can be used: white light interferometry uses an illumination source with short coherence length to determine the absolute position of the surface while confocal profilometry uses the principle of the defocus of light. As a relatively new technique, digital holography offers the simultaneous measurement of intensity and phase of a wave to generate a 3D image with the acquisition of just one single image. We give some application examples of these techniques to micro structures including deformation measurements