基于二值条纹动态照明的透明平滑曲面缺陷识别

Defects recognition of curved smooth transparent surface exploiting dynamic binary fringe lighting

针对在透明光滑表面视觉检测中,商用照明系统较难获取高对比度曲面瑕疵特征的局限性,论文提出了基于二值条纹的动态背向照明方法。该照明投影出一组等间距位移量的动态二值条纹图案,将亮暗条纹之间的过度区覆盖至整个待测表面,最大化缺陷与光滑表面的透射光线方向性差异。对动态条纹照明后的透明曲面序列图像均值处理后,获取均一背景下的缺陷特征图像。之后结合小波变换边缘提取与直方图全局阈值分割的方法,极大增强了光滑曲面与平面上的外观缺陷信息。基于3D曲面手机玻璃的测试结果表明,该方法成功提取出透明光滑曲面上的低对比度缺陷,为缺陷的准确识别提供了可靠保障,具有良好的应用前景。

High contrast feature of flaws on curved smooth transparent surface was hard to be captured by available commercial lighting systems.In consideration of the limitation of illumination for surface inspection,a back-light system exploiting dynamic binary fringe was presented.The lighting projected a set of dynamic binary fringes with equal interval movement,which contributed the transition zone between bright and dark stripe to cover the entire surface detected,and maximized the directional difference between light rays transmitted respectively by defect and flawless surface.The feature of defect with homogenous background could be obtained by averaging the curved transparent image sequences illuminated by dynamic binary fringe.Combined with edge extraction based on wavelet transform and global threshold segmentation based on histogram distribution,the appearance defects on both curved and flat surface were greatly improved.The test results of three dimensional curved mobile glass demonstrated that the method mentioned above could successfully extract low contrast defects on transparent curved surface,provide a reliable guarantee to recognize defects accurately,and has a good application prospect.