EOG (Electrooculogram)-based letter input interface controlled by  eye movements was developed to support communications of disabled individuals with motor paralysis. Horizontal and vertical EOG signals were measured using two electrodes attached above and beside the dominant eye and referring to an earlobe electrode and amplified with AC coupling. The cursor movements and a selection were indicated by eye movements or a voluntary eye blink. In preliminary experiments, the characteristics of eight directional eye movements were examined for user-friendly input operation. Six operations of down, left, right, lower left, lower right, and voluntary eye wink were assumed to be eye movements considering the accuracy of the input operations and the influence of the involuntary blink. Moreover, a hierarchical screen keyboard was proposed to improve the performance of the input interface even if the number of the operations was limited.

communication support, letter input interface, eye movement, AC-coupled electrooculogram, hierarchical screen keyboard.