A method is described for ordering the fringes in ordinary moire topograms that resolves hill-or-valley ambiguities. A photometric model is used to predict the expected surface brightness for the up and down surface orientation possibilities. Only one of the orientations produces estimates that are consistent with the measured values. The photometric model is based globally upon the moire geometry, and locally upon the surface reflectance properties. Topograms of test objects and human subjects are presented to illustrate the principle of photometric ordering.
James R. Pekelsky,
"Photometric Ordering Of Ordinary Moire Fringes", Proc. SPIE 0661, Optical Testing and Metrology, (25 November 1986); doi: 10.1117/12.938596; https://doi.org/10.1117/12.938596