In large-scale metrology, it is common to use contactless laser based distance measurement techniques, in particular through interferometry. The precision and flexibility demands on such systems as well as their mechanical repeatability are increasingly important. Using the properties of highly refractive spherical targets, the project aims to study in detail the optical characteristics of a system based on such targets, to verify the theoretical models with concrete optical setups and to create a modular demonstration instrument, whose performance will be validated using existing instrumentation.