Optical EngineeringMultireference fringe-pattern projection method for measuring the shape of an object with spatially isolated surfaces
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A multireference fringe-pattern projection (MRFP) method is developed for rapid measurement of the shape of an object that has spatially isolated surfaces. The method combines the commonly used fringe-pattern projection method and an acousto-optic deflector (AOD) scanner in one optical system. The AOD scanner generates reference fringes, whose positions can be conveniently adjusted to suit the respective object by changing the control signal to the AOD. We determined the accuracy of this MRFP method by measuring the displacement of a plastic plate and comparing the results with those obtained using a linear gauge. We find the relative accuracy to be 0.3%. To demonstrate the capability of this method to measure objects that have isolated surfaces, we use it to measure a vertical translation stage. Finally, we use it to measure the variations in position and shape of a fish while it is swimming. Such variation measurements are useful for studying the fluid dynamics of a swimming fish.