用无监督学习自动检测剪切散斑图像中的缺陷,减少对标注数据依赖。
Unsupervised Learning for Industrial Defect Detection: A Case Study on Shearographic Data
- 仅用无缺陷数据训练模型,通过特征匹配实现异常检测。
- 学生-教师模型在分类和定位上均优于自编码器,分离效果更佳。
- 适合工业质检场景,尤其适用于缺乏标注数据的环境。
剪切散斑是一种高灵敏度、全视野的无损检测方法,可用于发现内部缺陷。然而,其工业应用受限于需专家解读。为降低对标注数据和人工评估的依赖,本研究探索了剪切散斑图像中自动化异常检测的无监督学习方法。评估了三种架构:全连接自编码器、卷积自编码器及学生-教师特征匹配模型。所有模型仅使用无缺陷数据训练。构建了一个含可重复缺陷模式的定制试样,系统采集理想与现实变形条件下的剪切散斑数据。定义两个训练子集:一个仅含未变形无缺陷样本,另一个还包含全局变形但无缺陷的数据,模拟实际检测中由形变引起的条纹干扰。模型在二分类任务上评估,并对学生-教师模型进行空间缺陷定位评估。结果表明,学生-教师方法在分类鲁棒性方面表现更优,能实现精确定位;相比自编码器,其特征表示更具可分性(通过t-SNE可视化)。此外,以标注缺陷数据训练的YOLOv8作为参考基准,用于定位质量对比。研究表明,无监督深度学习有望实现工业环境中可扩展、标签高效剪切散斑检测。
原文摘要 · Abstract (English)
Shearography is a non-destructive testing method for detecting subsurface defects, offering high sensitivity and full-field inspection capabilities. However, its industrial adoption remains limited due to the need for expert interpretation. To reduce reliance on labeled data and manual evaluation, this study explores unsupervised learning methods for automated anomaly detection in shearographic images. Three architectures are evaluated: a fully connected autoencoder, a convolutional autoencoder, and a student-teacher feature matching model. All models are trained solely on defect-free data. A controlled dataset was developed using a custom specimen with reproducible defect patterns, enabling systematic acquisition of shearographic measurements under both ideal and realistic deformation conditions. Two training subsets were defined: one containing only undistorted, defect-free samples, and one additionally including globally deformed, yet defect-free, data. The latter simulates practical inspection conditions by incorporating deformation-induced fringe patterns that may obscure localized anomalies. The models are evaluated in terms of binary classification and, for the student-teacher model, spatial defect localization. Results show that the student-teacher approach achieves superior classification robustness and enables precise localization. Compared to the autoencoder-based models, it demonstrates improved separability of feature representations, as visualized through t-SNE embeddings. Additionally, a YOLOv8 model trained on labeled defect data serves as a reference to benchmark localization quality. This study underscores the potential of unsupervised deep learning for scalable, label-efficient shearographic inspection in industrial environments.
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