This thesis is developed within the framework of the European project ADAM, which aims to establish metrological traceability for Digital Twins of coordinate measurement systems. The characterization of three-dimensional surfaces is essential for assessing the form and topography of components. Coordinate measuring systems extend traditional Coordinate Measuring Machines (CMMs) by integrating optical measurement methods and non-Cartesian carriers. Among these, innovative measurement approaches enable the acquisition of surface topographies using focus variation microscopes mounted on collaborative robotic arms (cobots). The objective of this thesis is to develop a Digital Twin of a focus variation system by analyzing the sensitivity of measurements and systematic measurement errors with respect to key measurement parameters, such as wavelength, light intensity, and the geometry of the measured object..