Rayleigh - Sommerfeld diffraction theory to moiré measurement application

Shadow moiré method using surface warpage measurements, for some relatively smooth surface of the specimen or to obtain better precision, we have to use a smaller grating spacing, but often in light diffraction, was Measuring surface modulation information is covered, so that measurements can not proceed. In this paper, changing the optical path of the hypothesis, to solve this problem, and with Rayleigh - Sommerfeld diffraction theory, this paper proves the hypothesis.