Abstract: Automatic evaluation of X-ray weld image quality is an important foundation for automatic evaluation of weld image defects. A digital blackness meter model was proposed to realize the automatic evaluation of X-ray weld image quality. Firstly, in order to obtain the physical blackness by numerical calculation, the physical illumination model and the weld blackness model were combined by the digital blackness meter model. Then, through the analysis of the correlation between the physical blackness value of the sample image and the corresponding grayscale value, a method for obtaining the parameters of the digital blackness meter model was given. Finally, an X-ray weld film blackness automatic evaluation algorithm was proposed. The experiments on the actual X-ray weld images show that, the accuracy of the proposed algorithm can reach 99% without manual intervention. The cross-validation experiments show that the sensitivity of the proposed method is 98.5% and the specificity of the method can reach 100%. The digital blackness meter model based on illumination model and blackness model as well as the solving algorithm can replace the commonly used physical blackness meter and realize the automation of weld image quality evaluation.

Key words: X-ray weld image, defect detection, digital blackness meter, image quality evaluation

摘要： X射线焊缝图像质量自动评定是焊缝图像缺陷自动评定的重要基础。为实现X射线焊缝图像质量自动评定，提出了一种数字化黑度计模型。首先，为使该模型通过数字计算即可获得物理黑度值，数字黑度计模型同时融合了物理光照模型和焊缝黑度模型；然后，通过对样本图像的物理黑度值及对应灰度值的相关性分析，给出了数字化黑度计模型的参数求取方法；最后，提出了一种X射线焊缝底片黑度自动评定算法。在实际X射线焊缝图像上的实验结果表明，在完全无人工干预的情况下，所提算法的准确率可达99%。交叉验证实验表明，所提方法敏感度可达98.5%，特异度可达100%。基于光照模型和黑度模型的数字化黑度计模型及求解算法可以取代目前常用的物理黑度计，实现焊缝图像质量评定的自动化。

关键词: X射线焊缝图像, 缺陷检测, 数字化黑度计, 图像质量评价