Wrist-mounted laser rangefinder

The authors developed a small, lightweight rangefinder system which can be mounted on the wrist of a robot. Ranging takes place using a binary-coded projection method based on the principle of triangulation. The head of the range finger comprises a multi-slit projector with an infrared semiconductor laser, a nematic-cholesteric phase-transition (NCPT) liquid crystal shutter, and a small CCD camera. A head size of 170 mm/spl times/80 mm/spl times/50 mm and a weight of 230 grams were achieved. A dedicated image processor was developed to speed up range data generation. The time required to produce a range image is about 0.5 second. The system was tested on a real scene of a mechanical part, which is used in truss assembly in space.