Technical validation of the Di3D stereophotogrammetry surface imaging system

The purpose of this work was to assess the technical performance of a three-dimensional surface imaging system for geometric accuracy and maximum field of view. The system was designed for stereophotogrammetry capture of digital images from three-dimensional surfaces of the head, face, and neck. A mannequin head was prepared for imaging by adding texture in the form of red paint, and facial landmarks as black ink dots.

The mannequin was imaged at the manufacturer's recommended settings for human studies. Colour-coded surface difference images among repeated exposures were computed. We compared measurements of physical linear distance with digital measurements. The three-dimensional stereophotogrammetry system had a mean error in the three-dimensional surfaces of 0.057 mm, a repeatability error (variance) of 0.0016 mm, a mean error of 0.6 mm in linear measurements compared with manual measurements, and a field of view of 170 degrees horizontally and 102 degrees vertically.