Fiber optic fluid sensor using coated sensor tip

Claim 1

An optical fluid sensor comprising: a light emitter; a sensing tip element having at least one sensing surface; a sensing tip coating disposed over said sensing surface between said sensing tip element and the fluid to be sensed, such that the outer surface of said coating away from said tip element contacts the fluid when present, said coating being impermeable to the fluid and resistant to formation of residual fluid deposits; first optical fiber means connected to said light emitter and to said sensing tip element for transmitting light from said light emitter to said sensing tip; second optical fiber means connected to said sensing tip and to a photodetector, such that light emitted from said emitter is conveyed by said first optical fiber means to said sensing tip element, said light being substantially totally internally reflected in a first fluid condition and conveyed by said second optical fiber means to said photodetector for detection, said light being substantially completely refracted through said sensing surface and said coating in a second fluid condition; and electronic processing means for processing and displaying information from said photodetector.

Claim 10

A method of sensing fluid comprising: providing a light emitter; providing a photodetector for producing a signal in response to light incident thereon; providing a sensor tip in optical communication with said light emitter and said photodetector, said sensor tip including a substantially conical sensing tip element and a sensing tip coating over said sensing tip element to present a coated sensing tip surface in contact with the fluid to be sensed, said sensing tip coating being selected to be impermeable to the fluid to be sensed and resistant to the formation of fluid film of droplets thereon, said sensing tip element being selected from a material having an index of refraction n 1 and configured to have an internal angle of reflection B according to the formula ##EQU8## where n 2 =the coating index of refration, and a=the sensing tip bevel angle; providing electronic processing means connected to said photodetector for amplifying and displaying the signal from said photodetector; activating said light emitter to transmit light to said sensor tip, said light being transmitted through said sensor tip element to the tip element/coating interface, said light being refracted through said coating to the coating/fluid interface, said light at said coating/fluid interface being refracted into the fluid and lost when the fluid is present or reflected back into said coating in the absense of the fluid, said light reflected back into said coating in the absence of fluid being internally refracted and reflected within said coating and said tip element and directed to said photodetector to produce a signal processed by said electronic processing means to provide a display.

Claim 11

A method of sensing fluid comprising: providing a light emitter; providing a photodetector for producing a signal in response to light incident thereon; providing a sensor tip in optical communication with said light emitter and said photodetector, said sensor tip including a substantially conical sensing tip element and a sensing tip coating over said sensing tip element to present a coated sensing tip surface in contact with the fluid to be sensed, said sensing tip coating being selected to be impermeable to the fluid to be sensed and resistant to the formation of fluid film of droplets thereon, said sensing tip element being selected from a material having an index of refraction n 1 and configured to have an internal angle of reflection B according to the formula ##EQU8## where n 2 =the coating index of refration, and a=the sensing tip bevel angle; providing electronic processing means connected to said photodetector for amplifying and displaying the signal from said photodetector; activating said light emitter to transmit light to said sensor tip, said light being transmitted through said sensor tip element to the tip element/coating interface, said light being refracted through said coating to the coating/fluid interface, said light at said coating/fluid interface being refracted into the fluid and lost when the fluid is present or reflected back into said coating in the absense of the fluid, said light reflected back into said coating in the absence of fluid being internally refracted and reflected within said coating and said tip element and directed to said photodetector to produce a signal processed by said electronic processing means to provide a display.