Development of an Optical Motion Analysis System to Measure Small Movement in Three-Dimensional Space

H. Liu, S. Evans, C. Holt, A. Zhurov, and J. Middleton (UK)


Optical motion analysis, Small movement, Measurement.


Motion analysis techniques have been widely used in biomechanics for measuring large scale motions such as gait, but have not yet been significantly explored for measuring smaller movements such as the tooth displacements under load. In principle, very accurate measurements could be possible and this could provide a valuable tool in many engineering applications. The aim of this study was to investigate a novel method to measure small displacement in 3D space, as a step towards measuring tooth displacements to investigate the properties of the periodontal ligament. The characteristics of an optical motion analysis system have been evaluated using a wedge comparator with a resolution of 0.25µm to provide measured marker displacements in three orthogonal directions, for the diamond-shape and the spherical markers. The system accuracy, in the 20 200µm ranges, was ± 1.17%, 1.67% and ± 1.31% for the diamond marker in x, y and z directions, while the system accuracy for the spherical marker was ± ± 1.81%, 2.37% and ± 1.39%. The system repeatability measured under the different days, light intensity and temperatures for five times was ± 1.7µm, 2.3µm and 1.9µm for the diamond marker, and ± ± ± ± 2.6µm, 3.9µm and ± 1.9µm for the spherical marker in x, y and z directions, respectively. These results demonstrate that the system suffices accuracy for measuring tooth displacements and could potentially be useful in many other applications. ±

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