A fast opto-acoustic-pneumatic converter for benign and immune actuation

The opto-acoustic-pneumatic converter consists of a cylindrical cell having a pneumatic emitting and collecting tube at opposing ends, and exhaust vents on the side wall near to the collecting tube. Inside the cell a piezo disc is fixed to the face containing the emitting tube and is linked with a photodiode through a transformer-based matching circuit. The input optical signal is transmitted to the diode. A smooth pneumatic beam is emitted into the cylindrical cell through the emitting tube so that the flow normally remains laminar up to the collecting tube. With this arrangement, a pressure is built up in the collecting tube due to the entry of the laminar flow beam. The laminar flow may be disturbed by an acoustic signal at a specific frequency. When the acoustic signal is strong enough, the flow becomes turbulent in the cell, and as most of the flow is then exhausted from the side vents before entering the collecting tube, the pressure in the collecting tube is sharply reduced. The light is modulated at the specific frequency. The energy from the light causes the photodiode to produce a current to drive the piezo disc, and the piezo disc generates the required acoustic signal to control the pressure level in the collecting tube. Both the static and the dynamic performance of the converter have been investigated.<
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