光学学报, 2020, 40 (7): 0711003, 网络出版: 2020-04-15   

大口径反射镜表面颗粒污染物暗场检测算法研究 下载: 1189次

A Dark-Field Detection Algorithm to Detect Surface Contamination in Large-Aperture Reflectors
作者单位
1 哈尔滨工业大学机电工程学院, 黑龙江 哈尔滨 150001
2 中国工程物理研究院激光聚变研究中心, 四川 绵阳 621900
摘要
针对大口径反射镜表面污染物的成像特点,研究了污染物的暗场检测算法,包括图像采集过程中的自动聚焦算法,图像处理过程中的畸变校正与污染物提取算法等。就自动聚焦算法提出了粗-精结合的峰值搜索策略,并采用Tenengrad函数作为清晰度评价函数,获得了较高的聚焦精度。畸变校正算法在所建畸变模型的基础上,基于标定板角点的射影变换性质,求解畸变模型系数,实现了图像畸变校正,校正结果的方均根误差为3.3092 pixel。污染物提取算法采用顶帽变换去除图像背景,对去除背景的图像采用拉普拉斯算子加权自适应二值化算法提取污染物,该算法针对光照不均的小尺寸污染物图像的处理效果较好,检测结果数量误差为7%,检测精度优于全局阈值算法以及均值算子加权自适应二值化算法。该检测算法可以为反射镜表面洁净状态评估提供技术支撑。
Abstract
In this study, the dark-field detection algorithm, which is suitable for the detection of contaminants, is investigated in accordance with the imaging characteristics of the surface contaminants of the large-aperture reflector. In this algorithm, the autofocus algorithm is considered during the image acquisition process, whereas the distortion correction and pollutant extraction algorithms are considered during the image processing process. Further, the Tenengrad function is selected to evaluate the sharpness during the autofocus process, and a coarse-precision peak search strategy is proposed to improve the focusing accuracy. Based on the distortion model, the distortion correction algorithm calculates the distortion model coefficients in accordance with the projective transformation properties of the calibration plate corner points and implements image distortion correction. The root mean square error of the correction result is 3.3092 pixel. In the contaminant extraction algorithm, the top-hat transform is employed to eliminate the image background, and the Laplacian weighted adaptive binarization algorithm is used to extract contaminants from the background-removed image. The algorithm is effective for the image with small-sized pollutants in case of uneven illumination. The error in the amount of detected contaminants is 7%. The detection accuracy of the proposed method is better than those of the global threshold algorithm and the mean operator weighted adaptive binarization algorithm. Furthermore, the detection algorithm can provide technical support to evaluate the clean state of the reflector.

尹朝阳, 张德志, 赵林杰, 陈明君, 程健, 蒋晓东, 苗心向, 牛龙飞. 大口径反射镜表面颗粒污染物暗场检测算法研究[J]. 光学学报, 2020, 40(7): 0711003. Zhaoyang Yin, Dezhi Zhang, Linjie Zhao, Mingjun Chen, Jian Cheng, Xiaodong Jiang, Xinxiang Miao, Longfei Niu. A Dark-Field Detection Algorithm to Detect Surface Contamination in Large-Aperture Reflectors[J]. Acta Optica Sinica, 2020, 40(7): 0711003.

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