Method and Apparatus for the Non-Invasive Sensing of Glucose in a Human Subject

A method for a non-invasive sensing of biological analytes in a sample through spectrophotometric referencing utilizing two beams, each close in space, applicable to measuring interstitial fluid diffuse reflectance and comprising the steps of:

• a) providing an optics system utilizing a first radiation source, a second radiation source, a first radiation detector and a second radiation detector, thereby establishing four optical beam paths close in space through the system;
• b) modulating the sources with different time functions;
• c) configuring the optics system in a manner in which all optical elements of the optics system transmit and/or reflect the beams;
• d) separating a first pair of the beams and a second pair of the beams at one point in the system, focusing the first pair of beams on a user's skin and focusing the second pair of beams into a reference sample;
• e) demodulating signals produced by the first detector and the second detector and separating signals produced by the detectors from the beams;
• and
• f) computing a spectrophotometric transmittance as a ratio of a first ratio to a second ratio.