A laser based fiber optic sensor for measuring web velocity

A new fiber optic sensor for measuring web velocity is proposed. The sensor is based on the principle of laser doppler velocimetry and is primarily used to measure the longitudinal velocity (transport velocity) of the web. The frequency shift (doppler shift) of the light scattered from a moving particle contains information about the velocity of the particle. By measuring the doppler shift, velocity of the particle can be determined. Optical fibers are utilized in this sensor in order to provide flexibility in the location and orientation of the sensor in a web processing line. The use of these optical fibers are important in isolating the sensitive signal processing electronics from high temperature environments encountered in some web processing lines.