Abstract: The present invention provides a hollow prism for detecting liquid level in the presence of an optical beam, including a hollow member, dielectric members sealed to the hollow member with one of the dielectric members arranged at an inclined angle to the other, a sealed hollow space disposed between said dielectric members, wherein an incident optical beam enters through the first dielectric member at normal incidence and exits as an emergent beam through the second dielectric member, and wherein the emergent optical beam remains undeviated when the hollow member not immersed in a liquid medium and the emergent beam suffers deviation when immersed in the liquid medium. The present invention also provides a fiber optic liquid level detector with the hollow prism for detecting liquid levels.

Abstract: The present invention provides a hollow prism for detecting liquid level in the presence of an optical beam, including a hollow member, dielectric members sealed to the hollow member with one of the dielectric members arranged at an inclined angle to the other, a sealed hollow space disposed between said dielectric members, wherein an incident optical beam enters through the first dielectric member at normal incidence and exits as an emergent beam through the second dielectric member, and wherein the emergent optical beam remains undeviated when the hollow member not immersed in a liquid medium and the emergent beam suffers deviation when immersed in the liquid medium. The present invention also provides a fiber optic liquid level detector with the hollow prism for detecting liquid levels.