Patent ID: 6693285
Filing Date: 2004-02-17
Classification: G01F

Abstract:
A fluid interface position sensor comprising:a) a continuous optical waveguide, said waveguide having a waveguide refractive index and containing a fluorescent material that absorbs light at a first wavelength and re-emits light at a second wavelength, where said waveguide is immersed in a volume designed to contain a fluid interface between an upper fluid and a lower fluid, the upper fluid having larger refractive index than the lower fluid, where said waveguide further comprises a pump optical input positioned below the fluid interface and a fluorescent light output positioned above the fluid interface; b) a collimated pump source generating a collimated pump beam comprising light of the first wavelength; c) a fluorescence collector to collect light of the second wavelength, said light collector being in optical communication with said fluorescent light output; d) an optical conduit comprising an upper end through which said collimated pump beam is directed so as to emerge through a lower end which is in optical communication with the pump optical input of the continuous optical waveguide; and e) redirection optics positioned and oriented to redirect said collimated pump beam into the pump optical input at an angle such that the collimated pump beam is totally internally reflected within the continuous optical waveguide where the waveguide is contacted by the lower fluid and such that the collimated pump beam is refracted out of the waveguide where the waveguide is contacted by the upper fluid; wherein the light of the second wavelength is only emitted from the fluorescent material in the region of the waveguide that is contacted by the lower fluid, thereby providing an indication of the position of the fluid interface along the length of the waveguide.