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

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.