Microoptical distance sensor with integrated microoptics applied to an optical microphone

The developed fiber optical microphone (FOM) using intensity modulation of light is based on triangulation. Emitted light from an LED is directed through an optical fiber onto the membrane. The reflected light is coupled into the receiving fiber. Vibration of the membrane results in a toggling of the light spot on the receiving fiber. Consequently a change in intensity can be detected at the photo diode. The sensor characteristics are determined mainly by the coupling between the transmitting and receiving fiber. The crucial parameter is the steepness of the dependency of the transmitted intensity on the distance to the reflecting surface. We optimized the geometrical design parameters and developed an integrated micro-macro-interface with high precision self-adjustment for optical components - the micro optical distance sensor. Introducing new concepts by using integrated microoptics leads to a significant improvement of the sensor´s characteristics, such as higher sensitivity and dynamic range