Hough变换快速检测圆形PCB Mark

Fast detection of circular pcb mark using Hough transform

提出一种Hough变换检测圆形PCB(PrintedCircuitBoard,印刷电路板)Mark的方法。对检测图像进行阈值变换,并利用区域面积分割,将Mark区域和背景及噪声分离开来。计算Mark区域中心点,Hough变换圆心累加范围限制在这个中心点附近区域。依据Mark实际尺寸计算检测图像中Mark的半径,将累加器从三维降为二维。对检测图像进行Canny算子边缘检测后,采用先大间隔后小间隔的粗细累加策略,完成Hough变换检测。在全视觉贴片机SMT2505上应用表明,Mark中心检测误差和执行时间分别小于1个像素和50ms。继承了传统Hough变换检测精度高、抗噪能力强的优点,速度比传统Hough变换提高了2～3个数量级。

A method using Hough transform is proposed for the detection of circular PCB Mark. After threshold transform of test image, the region of Mark is separated from background and noise by area segmentation. By computing the center of the Mark region, the accumulating range of circle center in Hough transform is restricted near this center. Through calculation of the radius of the Mark on the test image based on practical mark size, the accumulator of Hough transform is changed from 3-dimension to 2-dimension. After edge detection of test image using Canny operator, the detection process of Hough transform is accomplished through rough-and-fine accumulation strategy which firstly uses big accumulating distance and then uses small distance. The application in full vision Mounter SMT2505 demonstrates that the average error of detection in center and the executive time are less than 1 pixel and 50ms respectively, which maintains the advantages of conventional Hough transform, such as high-accuracy and good performance in anti-noise and improves the processing speed for 2-3 orders of magnitude.