High-resolution temporal profilometry using Fourier estimation

To determine the topography of an object, spatial- and temporal profilometry techniques
have been developed with their corresponding strengths as and weaknesses. The main
weakness of phase-unwrapping techniques is the possible error in the unwrapped phase
due to large discontinuities in the model and sudden color changes. To eliminate the phaseunwrapping
step, we developed a new temporal profilometry technique that is insensitive
to discontinuities and color changes in the model under test. This chapter explains how
this technique is used to find the topography of an object. Our technique needs a series
of images of the test-object and a reference scan (a flat known surface) while projecting
varying fringe patterns. The grey values of each individual pixel in these images are determined
while increasing the frequency of the projected fringe pattern. Comparing these
grey values, the topography is calculated using the triangulation angle between camera and
projector. The technique is validated using custom-made simulation software. If large discontinuities
or sudden color changes are present in the object, the presented technique can
be a valuable method to scan the topography of the object under test.