Projection-type moiré contouring can be done without a reference grid by undersampling projected cosine fringes with a charged-coupled-device detector array to eliminate entirely the unwanted sum, shadow, and grid terms of classical moiré methods as well as the spurious moiré fringes that are due to higher harmonics. The technique produces a high-visibility sampled version of the moiré difference contour fringes. Higher-order aliasing can provide increased sensitivity when the same detector array is used. The sampling conditions are formulated as a moiré extension to the Whittaker-Shannon sampling theorem.
© 1984 Optical Society of America
Bernard W. Bell and Chris L. Koliopoulos, "Moiré topography, sampling theory, and charged-coupled devices," Opt. Lett. 9, 171-173 (1984)