Optical EngineeringHigh-speed surface profilometer based on a spatial light modulator and pipeline image processor
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A high-speed shape measurement system is developed based on the method of projected fringes. Sinusoidal fringes are projected onto the object using a commercial spatial light modulator, and the resulting fringe patterns are acquired by CCD camera at a rate of 30 s-1. The images are analyzed in real time using a pipeline image processor. The combination of phase shifting and temporal phase unwrapping enables discontinuous objects to be profiled as easily as continuous ones. An optimized sequence of fringe pitches is used in which the spatial frequency is reduced exponentially from the maximum value. A total time of 0.87 s is required from the start of the measurement process to the final display of a surface profile consisting of 250,000 coordinates. An accuracy of one part in 2000 was achieved with a maximum fringe density of 16 fringes across the field of view.