Development and evaluation of a wireless interface for inputting characters using Laplacian EMG.

We developed a compact wireless electrode containing an amplifier, a filter and a transmitter to measure the Laplacian electromyogram (Laplacian EMG) using the source derivation method. We made a character input system by connecting a circuit converting Laplacian EMG signals to clicks, with a personal computer in which a software for scanning character input was installed. We evaluated the system by comparing two integrated EMGs (IEMGs) measured with a conventional amplifier: one measured when the Laplacian EMG was used as an input signal to the system during a character inputting task, and the other measured when the conventional EMG was used. The IEMG was smaller in all of five subjects when the Laplacian EMG was used as the input signal than when the conventional EMG was used.