Phase feedback fibre interferometer for surface profiling

Advanced manufacturing techniques are producing increasing complex surfaces on the nano- and micro-scales. A fibre interferometer combined with a remote mountable optical probe is investigated with potential use for online measurement. The probe uses wavelength tuning to provide an optical 'stylus' which sweeps the surface. The method requires stabilising against fibre path length change due to temperature drift and vibration. This is done by wavelength multiplexing two light sources into the same optical path and using one as a tracking interferometer. An electro-optic modulator is used as the actuator in a control loop using real-time calculated phase feedback. This technique also counters polarisation evolution effects in the apparatus. Experiments are carried out to analyse noise in the stabilised interferometric setup. A step height sample is also measured to obtain a comparison between the instrument and a commercially available product.