摘要
高品质金属板带对于表面质量的要求非常严格,不允许存在一些微小的缺陷,现有的基于机器视觉的表面在线检测系统很难检测到微小缺陷。采用光度立体学的原理,利用两幅不同光照角度的灰度图像获得表面法向的方法检测表面微小缺陷。彩色三线阵电荷耦合元件(Charge-coupled device,CCD)摄像机安装在垂直于金属板带方向上,一台红光光源和一台蓝光光源对称安装在摄像机两侧。摄像机采集到的彩色图像可分离出R、G、B通道图像,其中R、B通道图像分别为红色、蓝色光源的反射光图像。表面倾角法可通过R、B通道图像计算表面倾角分布图,并根据表面倾角分布图检测微小缺陷。通过试验验证该方法可检测直径为0.1 mm的孔洞。讨论在一套检测装置中实现微小缺陷与常规缺陷同步检测的方案。在红光、蓝光两种光源基础上增加一台绿光光源,与摄像机形成介于明暗场的照明方式,可通过摄像机分离出的G通道图像检测金属板带表面的常规缺陷。
Requirement of surface quality for high-quality metal plates and strips is very strict, and tiny defect is not allowed on the surface. Existing surface inspection systems based on machine vision are difficult to detect tiny defects. Photometric stereo is applied to detect tiny surface defects with surface normal calculated from two gray images under different illumination angles. One color camera with triple line-scan charge-coupled device（CCD） is mounted perpendicular to the surface of the metal. One red lighting and one blue lighting are mounted symmetrically on both sides of the camera. Three channels of gray image including red, green, blue are separated from the color image captured by the camera, and red, blue channel gray images represent reflected lights of the red lighting and the blue light. The distribution map of surface slope angles is calculated from red and blue channel gray images with the developed algorithm. Tiny defects can be detected from the distribution map of surface slope angles. Experiments showe that pinholes with the diameter less than 0.1 mm can be detected. The scheme of detection normal defects and tiny defects with one apparatus is discussed. One green lighting is added, and mounted to the camera at the position between bight-field illumination and dark-field illumination. Normal defects can be detected from the green channel gray image of the camera which represents reflected lights of the green lighting.
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2013年第4期25-29,共5页
Journal of Mechanical Engineering
基金
'十二五'国家科技支撑计划(2012BAB19B06)
中央高校基本科研业务费专项资金(FRF-TP-09-027B)资助项目
关键词
金属板带
表面缺陷
表面检测
光度立体学
Metal plate and strip
Surface defect
Surface inspection
Photometric stereo
