为了实现对印制电路板线路线宽的精密测量，以同轴光源为AOI 系统的照明装置，采用图像处理技术，提取边

缘区域的灰度梯度特征并进行最小二乘曲线拟合，精确定位线路的边缘位置，进而计算得到线路线宽值。在此基础上，分析光

照对线宽测量造成的影响，提出基于熵的最佳光照强度调节方法以保证线路线宽的测量精度。通过实验证明，在最佳的光照

条件下，该方法可有效地保证测量精度，在成像比例为55.7um/像素条件下，平均误差为13um，约1/4像素。本文提出的方法

极具实用价值，对于同类型的、基于图像处理技术的精密测量研究具有参考价值。

In order to realize precise measurement for printed circuit board linewidth, Coaxial light is selected as AOI lighting system. Through image processing technology, the gradient feature around boundary region is extracted. And least squares curve fitting

is performed on gradient data, the precise position of boundary is located, so the measuring value of linewidth is calculated. Furthermore, for ensuring measuring accuracy, the research also analyzes relation between illuminator and measuring accuracy. And an illumination adjustment method based on entropy is proposed. After the method is implemented to achieve the best illuminator, the measuring result is pleasant, the average measuring error can be reduced to 13um, about 1/4 pixel on the condition that the image ratio is 55.7um per pixel. The method is very practical, and provides referent value to precise measuring work based on image processing technology.