Combined optical waveguide and prismatic liquid-level sensor

Abstract

In its preferred embodiment, a one-piece optical-prism sensor of liquid level internally incorporates waveguide structure, i.e., within the otherwise conventional conical external profile of the prism, the waveguide being a thin flat member which includes three parallel spaced axes, namely, the axis of light input, the central axis of the cone, and the axis of detection of such light as exits the prism. The conical shape of the prism is essentially a hollow conical shell, within which the waveguide extends in essentially a single diametrical plane, with integral connection of the shell to the diametric limits of the waveguide. The net result is that light enters the waveguide on the input axis and, to the extent that the light is internally reflected, the waveguide so confines internal reflection that scattering is very substantially reduced, and essentially all the internally reflected light will exit on the detection axis. And, for the case of liquid exposure to the outer surface of the prism, refraction into the liquid is more effective, while any internal reflected-light scattering is again very substantially reduced. Thus, by having so materially reduced internally reflected scattering, the sensor offers greatly enhanced sensitivity to the difference between a liquid exposure and a no-liquid (e.g. air) exposure of the prism.