Patent ID: 8743355

Claim:
An apparatus for measuring change in sugar concentration in a fluid relative to a baseline concentration, the apparatus comprising: a source of optical energy, said source having an emitter with an emission pattern; a first optical detector spaced a distance from said source; a second optical detector collocated with said first optical detector; a plurality of polarizers optically between said source and said detectors, said plurality of polarizers comprising: a first polarizer intersecting the emission pattern; and a second polarizer rotated relative to the first polarizer by a first rotational amount Θ, spaced a distance from the first polarizer, and proximal to said second optical detector, wherein said first polarizer is optically between said source and said second polarizer; a volume of liquid, said volume intersecting said emission pattern and positioned optically between said first polarizer and said second polarizer and optically between said first polarizer and said first detector; and at least one circuit coupled to said first optical detector and said second optical detector, said at least one circuit comprising: a compensating circuit coupled to said second optical detector; a subtractor circuit coupled to said compensating circuit and said first optical detector; and a gain circuit coupled to said subtractor circuit.