Fukunaga–Koontz Convolutional Network with Applications on Character Classification

• Published in: Neural processing letters Vol. 52; no. 1; pp. 443 - 465
• Main Authors: Gatto, Bernardo B., dos Santos, Eulanda M., Fukui, Kazuhiro, Júnior, Waldir S. S., dos Santos, Kenny V.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-08-2020; Springer Nature B.V
• Subjects: Artificial Intelligence; Artificial neural networks; Character recognition; Classification; Complex Systems; Computational Intelligence; Computer Science; Datasets; Deep learning; Discriminant analysis; Eigenvectors; Handwriting recognition; Neural networks; Subspaces; Subspace method; Fukunaga–Koontz transform; Shallow networks
• ISSN: 1370-4621; 1573-773X
• DOI: 10.1007/s11063-020-10244-5

Several convolutional neural network architectures have been proposed for handwritten character recognition. However, most of the conventional architectures demand large scale training data and long training time to obtain satisfactory results. These requirements prevent the use of these methods in a broader range of applications. As an alternative to cope with these problems, we present a new convolutional network for handwritten character recognition based on the Fukunaga–Koontz transform (FKT). Our approach lies in the assumption that Fukunaga–Koontz convolutional kernels can be efficiently learned from subspaces and directly employed to produce high discriminant features in a shallow network architecture. When representing image classes by subspaces, the within-class separability is reduced, since the subspaces form clusters in a low-dimensional space. To increase the between-class separability, we compute a discriminative space from the training subspaces using FKT. By learning convolutional kernels from subspaces, it is possible to extract representative and discriminative features from an image with only a few parameters. Another contribution of the proposed network is the use of pooling layers, which further improves its performance. The proposed method, called Fukunaga–Koontz Network (FKNet), is suitable for solving practical problems, especially when training and processing times are constraints. Four publicly available handwritten character datasets are employed to evaluate the advantages of FKNet. In addition, we demonstrate the flexibility of the proposed method by experiments on LFW dataset.