Speckle-based sensor system for real-time distance and thickness monitoring of fast moving objects

Real-time distance monitoring and thickness measurements of production lines are typical tasks of the manufacturing process. We demonstrate a novel optical sensor prototype capable of providing accurate distance measurements of fast moving objects. The principle of sensor operation is based on spatial filtering of dynamic speckles generated with a scanning laser beam. The sensor is able to measure the distance to opaque (metals, etc) and to multi-scattering materials (papers, plastics, etc). The presented sensor prototype provides measurements and data processing in real time. We verify sensor prototype performance of multi-scattering material (paper web) moving with a speed of 35 m s−1