Real-Time Japanese Sign Language Recognition Based on Three Phonological Elements of Sign

Abstract

Sign language is the visual language of deaf people. It is also natural language, different in form from spoken language. To resolve a communication barrier between hearing people and deaf, several researches for automatic sign language recognition (ASLR) system are now under way. However, existing research of ASLR deals with only small vocabulary. It is also limited in the environmental conditions and the use of equipment. In addition, compared with the research field of speech recognition, there is no large scale sign database for various reasons. One of the major reasons is that there is no official writing system for Japanese sign Language (JSL). In such a situation, we focused on the use of the knowledge of phonology of JSL and dictionary, in order to develop a develop a real-time JSL sign recognition system. The dictionary consists of over 2,000 JSL sign, each sign defined as three types of phonological elements in JSL: hand shape, motion, and position. Thanks to the use of the dictionary, JSL sign models are represented by the combination of these elements. It also can respond to the expansion of a new sign. Our system employs Kinect v2 sensor to obtain sign features such as hand shape, position, and motion. Depth sensor enables real-time processing and robustness against environmental changes. In general, recognition of hand shape is not easy in the field of ASLR due to the complexity of hand shape. In our research, we apply a contour-based method to hand shape recognition. To recognize hand motion and position, we adopted statistical models such as Hidden Markov models (HMMs) and Gaussian mixture models (GMMs). To address the problem of lack of database, our method utilizes the pseudo motion and hand shape data. We conduct experiments to recognize 223 JSL sign targeted professional sign language interpreters.