Inspection of micro-drills with "white light interferometry"

In the future, the inspection of micro-drills with diameters down to 50 µm will be required. Mechanical touch probes are inapplicable. Optical inspection is a challenging task. It requires high lateral resolution and a measuring volume much deeper than the depth of field. The microtopology of the object surface displays specular reflections under big angles. These problems can be overcome to a great deal, by a specifically designed White Light Interferometer and by an evaluation procedure that utilises implicite information about the measuring data. We introduce an instrument that measures geometrical parameters of micro-tools, most important, the cutting angle.