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US 10,473,586 B2Granted
Enhanced optical data capture using NDIR for liquids
AssigneeAirware, Inc.
InventorsThomas Campbell, Jacob Y Wong
Life of this patent
Estimating the term…
Abstract
The concentration of a targeted molecule (such as glucose) in a liquid medium having at least one interfering molecule coexisting with the targeted molecule is detected by use of NDIR and a sampling technique in which an imposed location of a pulse beam from a signal source, an interference source and a reference source is varied over a plurality of sites of a sampling area.
Claims11
An apparatus 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 MJ coexists with the targeted molecule, comprising:
- a signal source;
- an interference source;
- a reference source;
- a multiplexer and a collimator configured to pulse infrared radiation from the signal source, the interference source and the reference source into a pulsed beam which is directed at a first inclined angle (θi1) to a normal of a first spot of the liquid sampling matrix;
- a detector configured to detect infrared radiation after it emerges from the first spot as a first pulsed signal and reference channel output and a first pulsed interference signal and reference channel output from the pulsed beam after it penetrates into the first spot;
- means for changing the imposed location of the pulsed beam so that it is directed at a second inclined angle (θi2) to a normal of a second spot of the liquid sampling matrix and the detector is configured to detect infrared radiation after it emerges from the second spot as a second pulsed signal and reference channel output and a second pulsed interference signal and reference channel output from the pulsed beam after it penetrates into the second spot;
- signal processing for:
- obtaining a first average ratio value of Rave(t1) for a first preselected period of time (“t1”) from the first pulsed signal and reference channel output, where Rave(t1)=signal channel/reference channel output for the first preselected period of time;
- obtaining a first average ratio value of RJave(t2) for a second preselected period of time (“t2”) from the first pulsed interference and reference channel output, where RJave(t2)=interference channel/reference channel output for the second preselected period of time;
- obtaining a second average ratio value of Rave(t3) for a third preselected period of time (“t3”) from the second pulsed signal and reference channel output, where Rave(t3)=signal channel/reference channel output for the third preselected period of time, and
- obtaining a second average ratio value of RJave(t4) for a fourth preselected period of time (“t4”) from the second pulsed interference and reference channel output, where RJave(t4)=interference channel/reference channel output for the fourth preselected period of time;
- and
- electronics configured to use RJave(t2) and RJave(t4) to determine that a calibration curve is valid for the given time period and, if the calibration curve is valid, to calculate the concentration of the targeted molecule M in the liquid sampling matrix by use of Rave(t1), Rave(t3) and the calibration curve and provide the concentration of the targeted molecule M in the liquid sampling matrix as an output;
- 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 MJ, 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 MJ absorbs radiation at the signal wavelength;
- and
- 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 MJ will not pass in and out of the liquid sampling matrix within the preselected frequency.
14 more elements
A process for determining a concentration of a targeted molecule M within a given time period in a non-homogenous liquid sampling matrix in which at least one interfering molecule MJ 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 scanning sample of three or more spots of the liquid sampling matrix;
- detecting infrared radiation by a detector after it emerges from the scanning sample of three or more spots 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 scanning sample of three or more spots;
- using signal processing to obtain an average ratio value of Rave(t) for a first preselected period of time (“t”) from the pulsed signal and reference channel output, where Rave(t)=signal channel/reference channel output for the first preselected period of time;
- using signal processing to obtain an average ratio value of RJave(t2) for a second preselected period of time (“t2”) from the pulsed interference and reference channel output, where RJave(t2)=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 Rave(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 MJ, 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 MJ 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 MJ 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 Rave(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.
14 more elements
Dependencies are inferred from the claim text.