High-precision range finder for slowly moving target with rough surface

Simultaneous measurement of the range and velocity of a slowly moving target with a rough surface is demonstrated using a range finder with a self-mixing laser diode (LD). The accuracy of range and velocity measured simultaneously using the prototype range finder is a few percent and ten percent, respectively. The offset velocity measured for a resting target is 0.13 mm/s. The resolution of range measured for a resting target by the use of a revised range finder is improved to ±0.13% in a dynamic range of 0.2 m to 1 m. The improvement is achieved by introducing the reshaping of the FM modulation current of the LD. The range finder is suitable for detecting moving parts on a belt conveyor or obstacles placed in front of a mobile robot