Simultaneous range and velocity measurement using a frequency shifted feedback laser

Abstract

Laser Doppler velocimeters (LDVs) are non-contact sensors for measuring velocity, and generally used for measuring length of steel products. However, the distance range of the measurement target is restricted to a certain region in principle, making it difficult to measure the velocity of steel products with large distance fluctuations. To remove this restriction, a frequency-shifted feedback laser range and velocity meter (FSFL-RVM) was developed with an FSFL whose frequency changes proportionally with time at ultra-high speeds. This new sensor can measure the velocity without this restriction and additionally measure the distance without contact. The measurement accuracy was evaluated experimentally, and its measurement principle was verified. As a result, it was confirmed that its ability to measure velocities with the same accuracy as the LDV in a distance range five times that of the LDV and simultaneously measure distances within an accuracy of 0.1 mm.