[Development and application of an optical system to measure the movements of organs with soft tissue]

We proposed a new optical system to measure the movements of less accessible organs with soft tissue. The sensor unit is composed of a phototransistor and two LEDs. Two LEDs of light sources are driven by two phase signals with phase shift of 90 degrees. The distance between the sensor and the measuring object can be obtained as the function of the phase angle of reflex light signal detected by the phototransistor. The system can be easily constructed and provides simultaneous recordings of multiple points with the fast response in real time. The Relative precision is 0.5 mm and the resolution is 0.05 mm. Output characteristic of the system was less affected by the reflection factor of the object. We conducted to observe the tongue movements in speech production.