Scanning laser triangulation sensor geometry maintaining imaging condition

Abstract

This work deals with the system design, control and the experimental results of a scanning laser sensor in which the optical path is scanned by a novel high performance compact fast steering mirror (FSM). The system design satisfies the Scheimpflug condition even though only the illumination path is scanned, such that an FSM with a small aperture size and high bandwidth can be used. To scan the area of interest with the FSM, raster trajectories are employed, which provide an uniform spatial resolution over the scan area. To track the trajectory a feedback controller is designed using the H∞-approach, such that a closed loop bandwidth of 1.4 kHz is achieved. The FSM can follow triangular signals up to 200 Hz with the maximum actuation range of ±3°. This enables a framerate of up to two frames per second for an image with 100x100 pixels. With the scanning system a maximum spatial resolution of 60 μm and a scan range of 25 mm can be achieved.