INFRARED OPTICAL SENSOR FOR MEASURING INTERNAL INTERFACIAL WAVE MOTIONS

The absorption of infrared energy is used to infer internal interfacial displacements. The probe consists of an infrared emitting diode, operated in a pulsed mode, which projects a collimated beam of radiation across a fluid interface onto a silicon photodiode detector. The output of the diode feeds an amplifier and a sample‐and‐hold circuit. Through multiplexing, the electronics are capable of handling up to eight probes. The infrared sensor has a sensitivity of about 1 V/cm, and it may easily be used to resolve wave motions as small as 0.01 mm. © 1979, American Institute of Physics. All rights reserved.