A sampled-grating model of moire patterns from digital imaging

Abstract: "Traditional "crossed-grating" moire, as well as newer "sampled-grating" (scanning) moire, have proven to be effective methods of shape measurement. There is speculation that the moire patterns of a sampled grating, which are due to aliasing, can be modeled with crossed gratings. We compare the two and show that while crossed gratings can correctly predict the frequencies of a sampled grating, they cannot correctly predict the amplitudes. We go on to formulate a new model which accounts for multiple stages of sampling and transmission, and show how neglecting multiple stages can lead to mistakes in moire analysis. We demonstrate our model with an experiment using a digital imaging system."