Fast 3D profilometer based upon the projection of a single fringe pattern and absolute calibration

Abstract

We present a whole-field, 3D optical digitizer based on phase profilometry and on absolute calibration, which performs shape measurement through the projection of a single pattern of Ronchi fringes, and an absolute calibration of the optical head. A suitably developed procedure, based on accurate fringe analysis, implements phase extraction and allows univocal indexing of the field of view. Accurate models express, in a global reference system, both extrinsic and intrinsic parameters of the camera–projector pair. Proper calibration is performed for lens distortion compensation, and to obtain the absolute measurement of the shapes within a global reference system. The technique requires the acquisition of a single image, shows good robustness against fine variations of the fringe period and adapts well to the measurement of free-form shapes in a very short time. The system is portable, fully reconfigurable depending on the measurement requirements and suitable for a low-cost implementation. In this paper, we present the phase extraction method and the system calibration, and highlight the measurement performance of the digitizer in different set-ups, using free-form objects requiring multi-view acquisition.