ON THE USE OF OPTICAL FIBERS IN A PULSED TIME-OF-FLIGHT LASER RANGEFINDER

The pulsed time-of-flight laser rangefinding technique has been used in many industrial measurement applications, including 3D-coordinate measuring devices, hot surface profilers and mobile robot sensors. Optical fibres, typically 1-10 m in length and 100-400 mum in diameter can be used to guide optical pulses to the separate sensing head of the measurement device. The use of a large multimode fibre may cause problems, however, when aiming at millimetre accuracy, as the construction and adjustment of the optics of the sensor head may affect the transit time linearity and measurement accuracy via multimode dispersion. Environmental effects, such as bending, vibration due to the moving sensing head and temperature, also cause measurement errors. The error sources are studied and characterized in this paper.