Siamese Basis Function Networks for Defect Classification

Defect classification on metallic surfaces is considered a critical issue since substantial quantities of steel and other metals are processed by the manufacturing industry on a daily basis. The authors propose a new approach where they introduce the usage of so called Siamese Kernels in a Basis Function Network to create the Siamese Basis Function Network (SBF-Network). The underlying idea is to classify by comparison using similarity scores. This classification is reinforced through efficient deep learning based feature extraction methods. First, a center image is assigned to each Siamese Kernel. The Kernels are then trained to generate encodings in a way that enables them to distinguish their center from other images in the dataset. Using this approach the authors created some kind of class-awareness inside the Siamese Kernels. To classify a given image, each Siamese Kernel generates a feature vector for its center as well as the given image. These vectors represent encodings of the respective images in a lower-dimensional space. The distance between each pair of encodings is then computed using the cosine distance together with radial basis functions. The distances are fed into a multilayer neural network to perform the classification. With this approach the authors achieved outstanding results on the state of the art NEU surface defect dataset.