基于格雷码的分区间相位展开方法

Inter-partition phase unwrapping method based on Gray code

格雷码因具有良好的鲁棒性和抗噪性,被广泛应用到结构光投影三维成像方法中。在三维测量过程中,由于设备以及其他环境噪声的影响,格雷码方法解码条纹级次边沿和截断相位边沿通常无法处于理想的对齐状况,使得展开的相位出现跳变现象。为了更好地避免级次跳变误差,使得边沿跳变区域的容错宽度更大,提出基于格雷码的分区间相位展开方法。在互补格雷码基础上增加一幅格雷码图像,利用所有格雷码解得附加码字,通过对附加码字进行不同位移量的条纹级次映射,得到2个辅助条纹级次。利用所有条纹级次,对截断相位进行分区间相位展开,在边沿跳变区域错误大于半个周期时,仍能获取到无跳变现象的展开相位。实验结果表明,当边沿错误区域宽度小于3/4个条纹周期宽度时,可以有效避免级次跳变产生的误差。

Gray codes are widely used in structured-light projection three-dimensional(3D) imaging because of good robustness and noise immunity. During the process of 3D measurement, due to the influence of equipment and other environmental noises, the gray-code decoding fringe-order edge and the truncated phase edge usually cannot be in an ideal alignment state, which causes the unwrapped phase to jump. In order to better avoid the level hopping error and make the error tolerance width of the edge hopping region larger, an inter-partition phase unwrapping method based on Gray codes was proposed. A Gray code image was added on the basis of the complementary Gray code, the additional code words were obtained by decoding all the Gray codes, and two auxiliary fringe orders were obtained by performing fringe order mapping with different displacements on the additional code words. Using all the fringe orders, the inter-partition phase unwrapping was performed on the truncated phase. When the error in the edge hopping region was greater than half a period, the unwrapping phase without hopping could still be obtained. The experimental results show that when the width of the edge error region is less than 3/4 of the stripe period width, the error caused by the level hopping can be effectively avoided.