Search of a moving object and its range-image measurement using range-finding speedometer

We proposed a 3-D range-image measuring system for acquiring each shape of manufactured parts or works carried on a belt conveyer in factory automation. In the previous system, a light beam emitted from a laser diode was mechanically scanned simply once over the whole view area using two plane mirrors driven by each stepping motor. The resolution was limited by a minimum step angle of the stepping motor, and the measuring time by the number of measuring points. In this paper, we propose a new laser scanning method to get a higher resolution and to reduce measuring time for acquiring a 3-D range-image of a moving object. First, we scan the light beam to search an object in the whole view area with a large step angle, and after finding the object, the beam is scanned again only around the vicinity of the object with a small step angle. In searching a solitary square post (5 cm(H)×5 cm(W)×3 cm(D)) supported in a wide view area (13.8 cm×13.8 cm), the total measuring time 7.9 seconds (218 points) by the proposed method became greatly reduced compared with 14.3 seconds (361 points), which was required in the previous simple scanning method. In case of the same moving object, we could acquire its image in 5.6 sec. Thus, we succeeded in decreasing the number of measured points and measuring time keeping the resolution by the proposed beam scanning method. These results are a bit insufficient in actual application, however, by employing a scanning motor with a smaller step angle and a higher-speed signal processor, the measuring resolution and the measuring time will be further improved