This paper presents a novel tracking system combining the advantages of light-beam scanning and spread-spectrum techniques. Tracking is performed by scanning the tracking volume with several unique light patterns and detecting the variations in illumination at the tracked points. Due to the low correlation of the patterns, their phases can be individually detected and the absolute position of the detection point calculated. The light patterns can be produced with simple lamps using rotating shadow masks, yielding greater power and range while being safer and of lower cost than comparable lasers. The use of spread-spectrum sequences in the patterns makes the detection insensitive towards external or cross-coupled optical noise. A simple prototype system is demonstrated to be capable of an angular tracking accuracy of 2 mrad with a range of several meters. The limitations of the method together with some unconventional applications and modifications of the system are discussed.

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