3D shape reconstruction system for dielectric material specimens surface measurement

In this study, a 3D shape reconstruction system was assembled, by which the roughness of a piece of dielectric material specimen, also electrode configuration, can be measured without physical connection. The system, which consists of a CCD camera, a DLP projector and a desktop computer, was calibrated properly. The 3D shape reconstruction algorithm based on the phase shifting technology was put into practice by means of LabVIEW programming. The 3D data processing procedure includes phase wrapping, phase unwrapping and phase to depth calculation. In this research, both the 3-frame and the 4-frame phase shifting method were utilized to obtain a wrapped phase pattern, which was then unwrapped by the Goldstein algorithm and the quality map guided algorithm respectively to generate a continuous phase map. The result shows that the Goldstein algorithm is less time consuming while the quality map guided algorithm handles the residues better. The depth of the measured object was calculated from the phase difference of two corresponding pixels from the phase map of a reference plate and the phase map of the object.