A modified moiré technique for three-dimensional surface topography

In this paper we present an optical technique based on the shadow moiré method which allows the measurement and digitization of three-dimensional surfaces. The technique was tested through experimental work and the results were compared with those obtained by a coordinate measuring machine. Moving from the conventional shadow moiré method, new features were implemented enabling us to overcome the main shortcomings of the conventional moiré method. These include the need to assign the fringe order, the incapability of discerning concavity or convexity, the poor resolution and the complexity in the signal processing. All these problems have been solved by adding an element to generate a carrier fringe pattern to the equipment of the conventional shadow moiré technique and processing the obtained signal using the Fourier transform method. The proposed technique was applied to obtain external surfaces of sheet metal stamped parts. The experimental results show the effectiveness of this technique.