Rare Chinese character recognition by Radical Extraction Network

Building a modern Optical Character Recognition (OCR) system for Chinese is hard due to the large Chinese vocabulary list. Training images for rare Chinese characters are extremely expensive to obtain. Radical-based OCR systems tackle this problem by first extracting and recognizing basic graphical components (i.e., radicals) of a Chinese character. However, how to reliably recognize radicals still remains an open challenge. In this paper, we propose a novel Radical Extraction Network (REN) to extract and recognize radicals using deep Convolutional Neural Network (CNN). REN is end-to-end trainable, and it needs less hand-tunning compared with previous segmentation-based approaches. Deep appearance models for radicals are learned from data in a weakly supervised fashion, and no radical-level annotations are required. We learn to recognize different radicals on commonly used Chinese characters, and transfer the learned deep appearance models to rarely used Chinese characters. Experimental results show that the proposed method helps the classifier to recognize rare Chinese characters.