The XYZ positioning system is used to position the probe beam of the interferometer and to scan it over the region of interest. The positioning system is built around three SmarAct closed-loop positioners enclosed in a compact protective housing. Each positioner has a maximum scan range of 20 mm and a repeatability of 50 nm. The sensor head is mounted on the lowest positioner. The XYZ positioning system is mounted on a 25 mm diameter post so that its height is easily adjusted to accommodate samples of different dimensions. It is even possible to remove the positioning system from its mounting post in order to install it in a custom setup or to combine it with another instrument.