A NOVEL, ADAPTIVE SYSTEM FOR 3-D OPTICAL PROFILOMETRY USING A LIQUID-CRYSTAL LIGHT PROJECTOR

A 3-D optical whole-field profilometer based on adaptive projection of structured light is presented. The system is based on the projection of gratings by means of an LCD unit. The gratings can be varied both i n contrast and in period, to adapt to the shape of the object under me asurement. A video camera acquires at a different angle the object-def ormed pattern. Suitable pre-elaboration is performed, to decrease depe ndence on background illumination and nonuniform reflectivity of the s urface. Adaptive demodulation of the pattern allows the object profile to be evaluated. The performance of the instrument has been evaluated by means of a system calibration against a traceable high-precision c ommercial Contact Measuring Machine (CMM). The overall accuracy of the system is equal to 0.15 mm with a precision of 0.2 mm. In this articl e, the theoretical aspects of the technique are discussed, and the des cription of the complete system is presented. Profile reconstruction, calibration, and certification of the system are also covered. The acc uracy of the system is discussed, and experimental results are present ed.