Measurement of Microscopic Displacement and Vibration of Tympanic membranes by Means of Fiber Optics
Eiji Toba*, Kenchiu Riku*, Kazuya Ito** and Kiichiro Taguchi**
*Faculty of Textile Science and Technology, Shinshu University, Ueda
**Faculty of Medicine, Shinshu University, Matsumoto
A sensor by means of optical fiber bundle was developed for detecting microscopic displacement and vibration in tympanic membrance. Illuminating a planer object and detecting the reflected light with the bundle, we experimentally investigated the received optical intensity against the distance from the object. As a practical application to clinical examinations, we then measured the displacements and vibrations of tympanic membranes of a dog. The main results of the experiments are as follows. 1) The reflected intensity increases rapidly with the distance in the front slope region at a small distance, then it reaches the maximum at a certain distance. As the distance increases further into the back slope region, it decreases linearly. The straight portions of such an intensity-distance characteristics enable us to obtain displacements and vibration inversely from the intensity measured. 2) The displacement resolution is 0.05μm. The sensitivity is 9.85mV/μm for the region with L=0.1-0.5mm (front slope region) and 7.97mV/μm for L=1.0-1.7mm (back slope region). 3) The frequency response of a dog tympanic membrane was successfully measured for frequency range with 1008,000Hz. We conclude that the fiber optics bundle well detects the microscopic displacements and vibrations in tympanic membranes and its application to clinical examinations are expected.