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AN EVALUATION OF TIME-OF-FLIGHT RANGE CAMERAS FOR CLOSE RANGE METROLOGY APPLICATIONS

Time-of-flight range cameras are an emerging technology that produces a digital photo or video like output in which every pixel contains both intensity and distance information. Typical currently available off-the-shelf range imaging cameras offer spatial resolutions of up to 40 k-pixels, distance measurement precision of less than 1 cm, and accuracy of a few centimetres. These specifications seem poor for metrology applications, but significant improvements can be made with temporal and spatial averaging. We investigate and compare the SR4000 (Mesa Imaging) and XZ422 (Canesta Inc.) range cameras for close range metrology applications. As an example, we first describe a real-time person height measurement system. We then present range camera measurements of a three-dimensional reference object and compare to a photogrammetric survey to evaluate the precision and accuracy obtained. Results show that, with appropriate averaging, the range cameras can provide sub-millimetre precision. The accuracy results, however, are not as encouraging, at a few millimetres for the XZ422 camera and tens of millimetres for the SR4000 camera, with poor radial lens calibration the likely source of errors for the SR4000. Finally, we comment on the promising possibilities for the future of range cameras, assuming that the technology continues to improve.