Three-step phase-shifting is an extensively employed method for 3D shape measurement, especially for high speed 3-D image acquisition. However, since only three fringe images are used, the measurement result is susceptible to sensor and environment noise. In this paper, we propose a third harmonic injection technique for three-step phase shifting profilometry to reduce the error caused by the uncertainty noise. By adding a measure of third harmonic to the sinusoidal waveform, the amplitude of the sinusoidal fundamental component can be increased by 15.5-percent, which resulting in the reduction of the phase error caused by noise. Theoretical analysis, simulation, and experiment are presented to verify the effectiveness of the proposed technique.
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