Improvement of One-shot FringeProjection for Shape Measurement

Abstract

Fringe phase can be detected from one-shot image in shape measurement using color fringe
projection. However in practice, it is difficult to analyze the phase precisely because characteristics of
spectrum are depend on optical devices and test object. Improvement of measurement accuracy is attempted by
correction for detected hue information in this experiment. The hue distribution of the object is modified by
using reference hue of a flat surface. The accuracy is improved remarkably even if using general purpose
projector and digital camera. Moreover, spatial phase shift method using gray scale fringes is modified to
increase measurement accuracy, too. Phase of projecting pattern is shifted perpendicularly to projection
direction in advance and analyzed fringes along this direction. Un-uniformity of the measurement sensitivity
caused by optical arrangement is corrected by calculations of geometrical relationship. Because the shape
measurement is carried out by one-shot image in proposed methods whereas ordinary phase shift method
usually needs multiple images, those techniques are applicable to dynamic measurements. An example of
dynamic deformation is shown