Shadow moire profilometry by frequency sweeping

The frequency sweeping technique is proposed to measure the shape of objects with discontinuous height steps and/or spatially separated surfaces, which have been impossible to measure with conventional shadow moire topography. By controlling the amount of the rotation angle of the grating, the spatiotemporal moire patterns are produced with different contour intervals. The Fourier transform technique has been applied to analyze these patterns and obtain the temporal carrier frequency in which the height distribution of the object is involved. Experimental results show the validity of this method.