The FocusTracker FT uses a novel measuring principle to measure the focus position in a fast and easy way. This new system is able to measure two different ranges of divergence in one device. It can measure a fiber directly as well as an optical setup. Time resolution is up to 40 Hz. The FT helps to better understand and monitor the thermal behavior of an optical setup at your process parameters. It is available as water- or air-cooled version, for both VIS- or NIR wavelengths.