The phase shifting shadow moiré is an efficient technique for 3-D shape measurement. Our recent research focuses on improving its measurement accuracy without addition the complication of the experimental set-up. Considering that the existing measurement process of shifting shadow moiré technique is complex, we had been looking for ways to make it easier. In this paper we propose some effective techniques to fulfil the aim. In the proposed method, the binocular stereovision technique is used to calibrate the geometric parameters of our setup. Then a method is developed to determine the grating translation difference. After that an iterative self-tuning algorithm is use to retrieve the accurate phase. The proposed method is fast and can be implemented easily in many applications. Optical experiments are implemented to verify the feasibility of this method.
Shadow moiré fringes have a complex intensity distribution, which makes the existing arcsine function or arccosine function that is used in random phase-shift extraction algorithms unstable in applications. We propose a high-precision algorithm to determine the random phase shift in a robust way. The idea consists of constructing three consecutive fringe patterns by the addition of two background terms suppressed fringe patterns. Then, an iterative self-tuning phase-shifting algorithm is developed to extract the measurement phase in a pointwise manner. Due to the use of an iterative procedure and tangent function, the present method can evaluate the phase shift accurately and robustly and can be implemented easily in many applications. In addition, the proposed method provides a solution for the development of the two-frame random shadow moiré technique. We present simulation and optical experiments to demonstrate the correctness of the proposed method. The results show that the proposed method performs better than other methods.
Phase-shifting shadow moiré is an efficient technique for three-dimensional (3-D) shape measurement, but the technique is always suffered from the error of phase shifter. A three-frame random phase-shifting algorithm is proposed to relax the requirements of repeatability and accuracy of the phase shifter in a shadow moiré system. The proposed method can act as a bridge between the three phase-shifting analysis methods and two-shot phase-shifting methods. The value of introduced arbitrary and unknown phase shift can be calculated by a determinate formula. The algorithm has the advantages of being free from the disturbance of background elimination and less computation. In addition, the proposed method is immune to nonsinusoidal fringe patterns and can be implemented easily in many applications. Both simulation and optical experimental results verify the feasibility of this method.
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