Holographic Contouring Using Electronic Phase Measurement

The application of heterodyne and quasi-heterodyne (stepwise phase shifting) fringe interpolation techniques to contouring for 3-D object shape measurement is discussed. A setup with two spherical illumination sources for contour fringe generation is described. The contour fringe pattern can be observed in real time or from a holographic reconstruction. The use of a microcomputer for automated data acquisi-tion and processing allows one to determine the object shape for a large number of points and for arbitrarily shaped contour fringe surfaces. Experimental results are reported for both heterodyne and quasi-heterodyne phase measurement, offering a typical accuracy for object depth measurement of 0.2% of the lateral extension of the object.