快速三维重建的N级灰度编码法

N-ary Gray-level Coding Method for Fast 3D Reconstruction

基于灰度编码的条纹因易于编码和解码,在条纹投影轮廓术(Fringe Projection Profilometry,FPP)中有着广泛的应用,灰度编码方法通过给像素点设置不同的灰度值使得编码信息蕴含于图像之中。基于此,采用双灰度编码法,共投射五幅条纹图,其中包括三幅相移图像和两幅N级灰度编码图像。N级灰度编码图像经过解码后,可获取精确的条纹阶次信息,进而得到绝对相位信息。在解码过程中,使用两个交叉的二值掩膜对同级码字的码区进行统一解码,降低了因为条纹丢失或图像噪点引起的误差。与传统的灰度编码方法相比,新方法在不增加投射条纹数目的情况下获得了更加精准的编码信息。为验证该方法的有效性,进行了仿真实验和真实实验,实验结果表明可以有效获取物体表面三维形貌。

Gray coding strategy is widely used in fringe projection profilometry because it is easy to encode and decode.Grayscale coding method encodes coding information into an image by setting different grayscale values for pixels.This paper uses a double grayscale coding method to project a total of five fringe images,including three phase-shift images and two N-ary gray-level coding images.Accurate fringe order information can be obtained from the decoding of gray-level coding patterns,such that the smooth absolute phase is retrieved.In decoding stage,two crossed binary masks are proposed to uniformly decode the code area of the same level codeword,so as to reduce errors caused by fringe losing or image noises.The proposal can obtain more accurate coding information without increasing the number of fringe images in comparison to traditional gray coding method.In order to verify the effectiveness of this method,simulation experiments and real experiments are carried out.Experimental results show that this method can effectively obtain the three-dimensional morphology of object surface.