NDIR glucose detection in liquids

1. A process for determining a concentration of a targeted molecule M within a given time period in a liquid sampling matrix in which at least one interfering molecule M J coexists with the targeted molecule by use of a non-invasive apparatus, comprising the steps of:

pulsing infrared radiation from a signal source, an interference source and a reference source into a multiplexer and collimating radiation leaving the multiplexer into a pulsed beam which is directed at a spot of the liquid sampling matrix;

detecting infrared radiation by a detector after it emerges from the spot as a pulsed signal and reference channel output and a pulsed interference signal and reference channel output from the pulsed beam after it penetrates into the spot;

using signal processing to obtain an average ratio value of R ave (t) for a first preselected period of time (“t”) from the pulsed signal and reference channel output, where R ave (t)=signal channel/reference channel output for the first preselected period of time;

using signal processing to obtain an average ratio value of R Jave (t 2 ) for a second preselected period of time (“t 2 ”) from the pulsed interference and reference channel output, where R Jave (t 2 )=interference channel/reference channel output for the second preselected period of time;

determining a chosen calibration curve for the non-invasive apparatus;

using electronics to calculate the concentration of the targeted molecule M in the liquid sampling matrix by use of R ave (t) and the chosen calibration curve; and

providing the concentration of the targeted molecule M in the liquid sampling matrix as an output from said electronics;

wherein the signal source emits radiation at a signal wavelength which is within a first absorption band of the targeted molecule M, the interference source emits radiation at an interference wavelength which is within a second absorption band of said at least one interfering molecule M J , and the reference beam emits radiation at a reference wavelength which is neutral and is not within either the first absorption band or the second absorption band;

wherein said at least one interfering molecule M J absorbs radiation at the signal wavelength;

wherein the signal source, the interference source and the reference source are each pulsed at a preselected frequency of at least N Hz which is sufficiently fast so that a given molecule of the targeted molecule M or said at least one interfering molecule M J will not pass in and out of the liquid sampling matrix within the preselected frequency; and

wherein the chosen calibration curve is obtained by the steps of:

using the non-invasive apparatus to obtain a set of calibration curves for a set of different known concentration samples wherein each of the set of calibration curves contains a plurality of assumed β values, wherein β is a parameter indicating the ratio of the absorption strength of interfering molecules measured respectively at the signal wavelength and the interference wavelength;

using the non-invasive apparatus to calculate the concentration of the targeted molecule M in a known concentration calibration sample by use of R ave (t) and determining a best calibration curve of the set of calibration curves which achieves a calculated concentration closest to a known concentration of the known calibration sample; and

using the best calibration curve as the chosen calibration curve.

2. The process of claim 1 , wherein the pulsed beam is comprised of an alternate and sequential pulsing of a repeating pattern of the signal source, followed by the reference source, followed by the interference source, followed by the reference source.

3. The process of claim 1 , wherein the pulsed beam is comprised of an alternate and sequential pulsing of a repeating pattern of the signal source, the reference source and the interference source.

4. The process of claim 1 , wherein the frequency of N Hz is greater than 1.0 KHz with a duty factor of at least 10%.

5. The process of claim 1 , wherein t=t 2 .

6. The process of claim 1 , wherein the signal beam has a signal beam center wavelength of 1,150 nm (1.150μ) and the reference beam has a center wavelength of 1,064 nm (1.064μ).

7. The process of claim 6 , wherein the interference beam has a center wavelength of 1,210 nm.

8. The process of claim 7 , wherein the targeted molecule M is glucose.

9. The process of claim 8 , wherein said at least one interfering molecule M J is comprised of a plurality of interfering molecules contained in a body interstitial fluid.

10. The process of claim 1 , wherein radiation emerging from the spot is collected by a lens onto the detector.