From the Doppler Effect to Ultrafast Distance Metrology

The fast inspection of technical processes gains increasing importance. Time resolved distance and shape measurements of the dynamic deformation of high speed rotating objects are challenging. The measurement rate of conventional distance sensors is limited, since their uncertainty strongly increases with the surface velocity of the inspected object. In contrast, the recently developed laser Doppler distance sensor exhibits a distance measurement uncertainty which is independent of the lateral surface velocity. This unique measurement feature allows ultrafast inspection of high-speed objects such as rotors of turbo machines.