Development of a 3D clinical facial imager
Stephen J. Marshall, R. C. Rixon, Don N. Whiteford, J. T. Cumming, Peter J. Wells, S. J. Powell · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1993
A collaborative project between NEL and St George's Hospital to investigate the measurement of the human face has resulted in the development of a 3-D clinical facial imager. The system utilizes the projection moire fringe contouring method developed at NEL to acquire accurate 3-D coordinates from the surface of a patient's face. In order that data can be obtained from the full facial area, two moire measuring units are employed, positioned symmetrically to each side of the face. The phase-stepping technique is used to improve the accuracy of interpolation between fringe centers and to distinguish automatically between surface concavity and convexity. Digitization and analysis of the resulting fringe patterns is performed using CCD cameras linked to a PC-hosted transputer image processing board which also controls the operation of the measuring units. Output is in the form of a dense mesh of 3-D coordinates which are transferred to a graphics workstation for image display, manipulation, and interrogation using specially developed software. A detailed description of the facial imager is given, with particular emphasis on the design features and two-stage calibration method which ensure that the inherent accuracy of the data acquisition technique is realized and facilitate the reliable measurement of unrestrained patients.