为了获得连续相位板(CPP)焦斑的外形尺寸，提出一种焦斑边缘轮廓的提取方法。连续相位板焦斑图像内部梯度起伏较大，直接应用传统边缘检测方法，易形成内部伪边缘。通过对焦斑图像依次作梯度处理、阈值分割、空间扫描和椭圆拟合，可以有效地获取焦斑边缘轮廓。比较了分别采用Laplace,Sobel,Krisch,Log算子进行梯度处理的提取结果，结果表明: 采用Krisch算子，焦斑边缘轮廓提取的结果更稳定可靠。比较了阈值分割时不同阈值情况下的提取结果，表明阈值选取在背景梯度均值的110倍至180倍时，焦斑边缘轮廓提取结果比较可靠。

In order to obtain the size of a focus spot of continuous phase plate (CPP), an edge-abstracting method is proposed. It is possible to acquire a false edge profile if traditional edge-abstracting methods are used because CPP focus spot image has a great grayscale grads. After the operations of grads processing, threshold segmentation, spatial scanning and ellipse fitting, the focus spot edge can be obtained. The edge-abstracting results are compared separately with Laplace, Sobel, Krisch, Prewitt, Log arithmetic operators for grads processing, which shows that the results are more robust and reliable if Sobel or Prewitt arithmetic operators are used. And the abstracted results are compared with different threshold values for threshold segmentation, which shows the results are more reliable if the threshold value is 110 to 170 times of the grads mean value of the background grayscale levels.