Optical liquid level indicator

Claim 2

An optical device for detecting the level of liquid within a container comprising a hollow standpipe for holding liquid at the level of the liquid within the container, a light source outside the standpipe aT one side and a single light detector outside the standpipe at the opposite side, the source and detector being extended along the standpipe, means for focusing an intense light beam onto the detector from the light source only where liquid is in the light beam between the source and the detector and for focusing a weak light beam onto the detector where liquid is absent between the source and the detector, said means comprising an optical system including a lens in each side of the standpipe aligned with the light source and detector for directing the light from the source toward the detector, and diaphragm means within the standpipe for defining an elongated slit aligned with the source and the detector, the optical parameters being chosen to focus an intense light beam through the slit and onto the detector where liquid is in the light beam between the lenses and where liquid is not in the light beam to direct a major portion of the light onto the diaphragm so that a relatively weak light beam passes through the slot to the detector, whereby the total amount of light reaching the detector is a function of the liquid level.

Claim 3

An optical device for detecting the level of liquid within a container comprising a hollow transparent standpipe for holding liquid at the level of the liquid within the container, a light source outside the standpipe at one side and a single light detector outside the standpipe at the opposite side, the source and detector being extended along the standpipe, means for focusing an intense light beam onto the detector from the light source only where liquid is in the light beam between the source and the detector and for focusing a weak light beam onto the detector where liquid is absent between the source and the detector, said means comprising an optical system including a diaphragm having an elongated slit centrally disposed within the standpipe and aligned with the source and detector, and a cylindrical plano-convex lens integrally formed in each side of the standpipe aligned with the light source and detector, one of the lenses being formed to focus the light beam through the slit to the other lens only in the presence of liquid, the other lens formed to focus the light onto the detector, the one lens directing a major portion of the light beam onto the diaphragm in the absence of liquid so that a relatively weak light beam reaches the detector whereby the total amount of light reaching the detector is a function of the liquid level.

Claim 4

An optical device for detecting the level of liquid within a container comprising a hollow transparent standpipe for holding liquid at the level of the liquid within the container, a light source outside the standpipe at one side and a single light detector outside the standpipe at the opposite side, the source and detector being extended along the standpipe, means for focusing an intense light beam onto the detector from the light source only where liquid is in the light beam between the source and the detector and for focusing a weak light beam onto the detector where liquid is absent between the source and the detector, said means comprising an optical system including a diaphragm having an elongated slit centrally disposed within the standpipe and aligned with the source and detector, and a cylindrical plano-convex lens integrally formed in each side of the standpipe aligned with the light source and detector, one of the lenses being formed to focus the light beam through the slit to the other lens only in the presence of liquid, the other lens formed to focus the light onto the detector, the one lens directing a major portion of the light beam onto the diaphragm in the absence of liquid so that a relatively weak light beam reaches the detector whereby the total amount of light reaching the detector is a function of the liquid level.

Claim 5

An optical device for detecting the level of liquid within a container comprising a hollow transparent standpipe for holding liquid at the level of the liquid within the container, a light source comprising a lamp and a fiber optic light conductor terminating in an elongated light emitter outside the standpipe at one side and a light collecting means comprising a fiber optic light conductor having an elongated light collector outside the standpipe at the opposite side and terminating at a single light detector, means for focusing an intense light beam onto the collector from the light emitter only where liquid is in the light beam between the emitter and the collector and for focusing a weak light beam onto the collector where liquid is absent between the emitter and the collector, said means comprising an optical system including a lens formed in each side of the standpipe aligned with the light emitter and collector for detecting the light from the source toward the detector, and diaphragm means within the standpipe for defining an elongated split alinged with the emitter and the collector, the optical parameters being chosen to focus an intense light beam through the slit and onto the collector where liquid is in the light beam between the lenses and where liquid is not in the light beam to direct a major portion of the light onto the diaphragm so that a relatively weak light beam passes through the slit to the collector whereby the total amount of light reaching the detector is a fuNction of the liquid level.

Claim 6

An optical device for detecting the level of liquid within a container comprising a hollow transparent standpipe for holding liquid at the level of the liquid within the container, a light source comprising a lamp and a fiber optic light conductor terminating in an elongated light emitter outside the standpipe at one side and a light collecting means comprising a fiber optic light conductor having an elongated light collector outside the standpipe at the opposite side and terminating at a single light detector, means for focusing an intense light beam onto the collector from the light emitter only where liquid is in the light beam between the emitter and the collector and for focusing a weak light beam onto the collector where liquid is absent between the emitter and the collector, said means comprising an optical system including a lens formed in each side of the standpipe aligned with the light emitter and collector for detecting the light from the source toward the detector, and diaphragm means within the standpipe for defining an elongated split alinged with the emitter and the collector, the optical parameters being chosen to focus an intense light beam through the slit and onto the collector where liquid is in the light beam between the lenses and where liquid is not in the light beam to direct a major portion of the light onto the diaphragm so that a relatively weak light beam passes through the slit to the collector whereby the total amount of light reaching the detector is a fuNction of the liquid level.