Three diode optical bridge system

• US 20070208238A1
• Filed: 09/25/2006
• Published: 09/06/2007
• Est. Priority Date: 04/26/2002
• Status: Active Grant

• Current Assignee: Grove Instruments, Inc.
• Original Assignee: Grove Instruments, Inc.
• Inventors: Burrell, Rebecca, Kun, Stevan, Harjunmaa, Hannu, Leuenberger, Georg
• Granted Patent: US 8,175,666 B2
• Time in Patent Office: Days
• US Class Current: 600/316
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence
• CPC Class Codes: G01N 21/35 using infrared light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/49 within a body or fluid

Abstract

An improved method for non-invasively measuring a concentration of a target analyte dissolved in a fluid flowing through a sample is presented. It includes directing a probe beam of electromagnetic radiation, consisting of time multiplexed components of different wavelengths, where at least one of the time-multiplexed components consists of two different simultaneous wavelengths, whose intensity relation defines the effective wavelength of their combination, through the sample and measuring the difference of the absorption of the radiation of the time-multiplexed components at different sample states. During sample state changes, the amount of fluid containing the target analyte within the sample is changing, which varies the total amount of target analyte in the sample, as well as the absorption properties of the sample. The sample states are produced, for instance, by compressing and uncompressing the tissue sample. The accuracy of the presented method is enhanced by including continuous estimation of the amount of the fluid containing the target analyte within the sample, and measurement of the variations of the absorption at a wavelength at which the target analyte absorbs significantly. The method is particularly useful in measuring the concentration of a target analyte, such as glucose, in tissue containing blood. An apparatus for performing this method also is disclosed.

Claims

1. A method of generating a beam of electromagnetic radiation for the non-invasive measurement of a concentration of a target analyte in a fluid within a sample matrix, the method comprising:

directing a combined beam of electromagnetic radiation at the sample, the combined beam including at least two repetitive periods of radiation having different wavelengths, the target analyte having different absorption coefficients for the different wavelengths, and where the radiation during at least one period of radiation consists of a mixture of at least two radiations of different wavelengths, having an effective wavelength equal to the intensity-weighted mean of the two component wavelengths.

2. The method according to claim 1, wherein the sample matrix comprises biologic tissue and the fluid comprises blood.

3. The method according to claim 1, wherein the wavelengths of the wavelength pair are selected to minimize the detected transmission or reflection difference between the wavelength periods measured during a sample state.

4. The method according to claim 1, wherein the intensities of the periods of radiation are adjusted when the sample is at a first sample fluid state, and at least one of the effective wavelengths of the at least two repetitive periods of radiation is selected to minimize the detected transmission or reflection difference when the sample is at a state different from the first state.

5. The method of claim 1, wherein the wavelength that is strongly absorbed by glucose is substantially in the range of 1550 to 1700 nm, and the wavelength lightly absorbed by glucose is substantially in the range of 1350 to 1430 nm.

6. The method of claim 1, wherein the combined beam is produced by three or more diode lasers.

7. The method of claim 6, wherein at least one laser diode produces a primary radiation beam during a first period of radiation, and at least two laser diodes produce an effective reference beam during a second period of radiation.

8. A system for the non-invasive measurement of a concentration of a target analyte in a fluid within a sample matrix, comprising:

a source of electromagnetic radiation that directs a combined beam of electromagnetic radiation at the sample, the combined beam including at least two repetitive periods of radiation having different wavelengths, the target analyte having different absorption coefficients for the different wavelengths, and where the radiation during at least one period of radiation consists of a mixture of at least two radiations of different wavelengths, having an effective wavelength equal to the intensity-weighted mean of the two component wavelengths.

9. The system of claim 8, wherein the source of electromagnetic radiation comprises three or more laser diodes.