Abstract
Digital holographic microscopy (DHM) is an imaging technique, which can be applied to the visualisation and metrology of microscopic objects. It has been established in the frame of the DISCO project that DHM can be considered as an efficient method for direct comparison of the shape or deformations of two objects. “Comparison DHM” allows a straight comparison with a gauge provided by a manufacturer or customer. The phase subtraction between ideal and actual wavefront of the object provides data equivalent to those given by a Twyman–Green or a Mach–Zehnder interferometer.