Optical microscopy is the most basic technique for observing topography, microstructure and small features in material science. It uses visible light and a system of lenses to magnify images. Optical microscopy is limited by a narrow depth of field but its use can be enhanced by interferometric techniques. Image acquisition and processing takes approximately 5 minutes. The magnification range from 1x to 100x. Geometries with steep flanks, highly reflective properties and strong roughness are measured with a vertical resolution up to 10nm. In the DefectLab two optical microscopes are available. Olympus LG-PS2 with XY table and one Leica S8AP0. Both are installed with a camera.