利用频率编码的少图像相移轮廓术

Phase-Shifting Profilometry with Fewer Images Using Frequency Coding

为了减少相移轮廓术所需投影和采集的条纹图像数量,提高三维测量速度,提出了一种新的相位展开方法。首先,在3步相移模式下额外投影1张在固定位置频率跳变的余弦编码图像,从捕获的4张图像中计算余弦真值;其次,利用在不同周期内绝对相位和余弦真值间不同频率的余弦关系,通过迭代插值的方式获得相位截断点,并进行相位展开;最后,对截断点附近出现的阶次跳变误差通过三分相位的方法进行校正。实验结果表明,本文方法仅需4张图像就可以完成多频模式下的时域相位展开,并且不受相位中断的影响。当相移图像周期数为15时,相位解算结果和多频递进方法一致。

A novel phase-unwrapping method is proposed to improve the speed of three-dimensional measurement by reducing the number of fringe images required for projection and acquisition in phase-shifting profilometry.First,an additional cosine-coded image with a fixed position frequency jump is projected under a three-step phase-shifting mode.The cosine truth value is calculated from four captured images.Second,the cosine relationship between the absolute phase and cosine truth value at different frequencies within different periods is utilized.Phase discontinuity points are obtained,whereby phase unwrapping is performed through an iterative interpolation method.Finally,the order jump errors that occur near the discontinuity points are corrected using a three-phase method.In line with the experimental results,the proposed method required only four images for temporal phase unwrapping in multi-frequency mode and was unaffected by phase interruptions.When the number of phase-shifting image period was 15,the phase calculation results were consistent with the multi-frequency progressive method.