Abstract
Finger tracking using motion sensor has been attractive technique for non-contact operation of electric devices. Piezoelectric ultrasonic sensors can be applied to the motion sensing by the detection of the reflected waves from objects. The piezoelectric sensor, however, is impossible to detect the motion at close range because the several ultrasonic waves are overlapped. In this study, the array of electret condenser sensors with film lamination (FilmECS) was fabricated to track a finger above a mobile device. The receiving sensitivity, the transmitting power and the sensitivity of transmitting and receiving were measured to investigate the characteristics of the sensor array. The resonance peak of the fabricated FilmECS was estimated to 50-60 kHz and around 70 kHz for receiving and transmitting, respectively, Furthermore, the sharp reflected waveform from an artificial finger was obtained by the FilmECS at transmitting and receiving. Eventually, the location of the fingertip could be detected at the distance up to 3 cm between the array and the fingertip.
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