单线阵CCD系统的表面凹坑缺陷检测方法

Study and modeling for surface pit defect detection based on linear array CCD system

为解决表面凹坑缺陷与其他平面表面缺陷同时在线检测的问题,提出一种基于单线阵CCD系统进行表面凹坑缺陷检测的方法.根据光辐射照射模型和相机成像模型,建立了基于单线阵CCD的凹坑检测数学模型,由模型推导出图像像素灰度与凹坑深度的关系,利用特定光源和光照角度的关系,进行表面凹坑缺陷的检测.结果表明,由于凹坑边缘部位深度的渐变引起CCD输出电压信号的渐变,凹坑图像呈现边缘像素灰度渐变现象,且随光源光照角度的降低,凹坑图像特征更加突出.边缘灰度渐变的图像特征成为凹坑缺陷与其他平面缺陷相区别的重要特征,有利于凹坑缺陷的检测与识别.

To solve the problem of simultaneous detection of pit defect and other planar defects, a pit defect detection method based on single linear CCD system is developed. On the basis of light radiation, light illumi- nation and camera imaging model, the mathematic model for pit detection based on single linear CCD system is deduced. The mathematic model indicates the relationship of image pixel gray level and pit depth. By making use of the structure of special light source and illumination angle, the surface pit defect can be detected. The experimental results show that the gradual change of pit edge depth causes the gradual change of CCD output voltage signal, and then causes the gradual change of pit image edge gray level. The lower the illumination an- gle, the more obvious the image feature. The image feature of edge pixel gray level gradual change the most important feature for the distinction of pit defect and other planar defects, which contributes defect detection and recognition. becomes to the pit defect detection and recognition.