An optical sensor for detecting the contact location of a gas-liquid interface on a body

Abstract

An optical sensor for detecting the dynamic contact location of a gas-liquid interface along the length of a body is described. The sensor is developed in the context of applications to supercavitating bodies requiring measurement of the dynamic cavity contact location; however, the sensing method is extendable to other applications as well. The optical principle of total internal reflection is exploited to detect changes in refractive index of the medium contacting the body at discrete locations along its length. The derived theoretical operation of the sensor predicts a signal attenuation of 18 dB when a sensed location changes from air-contacting to water-contacting. Theory also shows that spatial resolution (d) scales linearly with sensor length (L(s)) and a resolution of 0.01L(s) can be achieved. A prototype sensor is constructed from simple components and response characteristics are quantified for different ambient light conditions as well as partial wetting states. Three methods of sensor calibration are described and a signal processing framework is developed that allows for robust detection of the gas-liquid contact location. In a tank draining experiment, the prototype sensor resolves the water level with accuracy limited only by the spatial resolution, which is constrained by the experimental setup. A more representative experiment is performed in which the prototype sensor accurately measures the dynamic contact location of a gas cavity on a water tunnel wall.

Muscle Sensing Device Design Using a PANDA Ring Resonator System

“…Optical devices are rapidly developing and spreading. These have unique properties such as greater sensitivity, selectivity, are non-invasive, small size amongst others, which have become attractive options in various applications; for instance, communications, microbiology, automotive industry, surveillance and monitoring domains, and so on [1]- [4]. Furthermore, the current trend of numerous health care methodologies directly impacts the research and development of optical sensor devices which enable these new technologies to reduce patient trauma and recovery times and lower healthcare costs.…”