TRACKING LASER-RADAR FOR 3-D SHAPE MEASUREMENTS OF LARGE INDUSTRIAL OBJECTS BASED ON TIME-OF-FLIGHT LASER RANGEFINDING AND POSITION-SENSITIVE DETECTION TECHNIQUES

A tracking laser radar device is proposed for the 3-D measurement of t he shapes of large industrial objects. The measuring system includes a servo-controlled measuring head and small reflectors attached to the object. The sensor consists of a tracking sensor, a pulsed time-of-fli ght rangefinder and angle encoders. The implementation of the tracking sensor and its test results are explained in detail. Tracking is acco mplished by illuminating the reflectors of the target object and focus ing the reflected light on the surface of a four-quadrant (4Q) positio n-sensitive detector, the signals of which are used to drive the servo motors of the measuring head. The test results show a tracking sensor resolution of about 0.003 mm (sigma value) and bias of about +/-0.1 m m when the distance and angle of the target reflector vary in the rang es 2-5 m and +/-45-degrees, respectively. The pointing accuracy of the tracking system was better than +/-0.3 mm.