moire topography method is a well-known non-contacting 3-D measurement method. Recently, the automatic 3-D measurement by moire topography has been required, since the method was frequently applied to the engineering and medical fields. The 3-D measurement using projection moire topography is very attractive because of its high measuring speed and high sensitivity. In this paper, using two-wavelength method of projection moire topography was tested to measuring object with 2n-ambiguity problems. The experimental results prove that the proposed scheme is capable of finding absolute fringe orders, so that the 2n-ambiguity problems can be effectively overcome so as to treat large step discontinuities in measured objects.
