Three diode optical bridge system

• US 8,175,666 B2
• Filed: 09/25/2006
• Issued: 05/08/2012
• Est. Priority Date: 04/26/2002
• Status: Active Grant

• Current Assignee: Grove Instruments, Inc.
• Original Assignee: Grove Instruments, Inc.
• Inventors: Harjunmaa, Hannu, Kun, Stevan, Burrell, Rebecca, Leuenberger, Georg
• Primary Examiner(s): Winakur, Eric
• Assistant Examiner(s): Fardanesh, Marjan
• Application Number:
  US11/526,564
• Publication Number:
  US 20070208238A1
• Time in Patent Office: 2,052 Days
• Field of Search: 600300-344, 422 681- 8213, 250330-334
• 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, having time multiplexed components of different wavelengths, where at least one of the time-multiplexed components consists of two different simultaneous wavelengths 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, varying the total amount of target analyte in the sample, and the absorption properties of the sample. The sample states may be produced by compressing and uncompressing the tissue sample. The method is useful in measuring the concentration of a target analyte, such as glucose, in tissue containing blood.

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 including a principal beam and a reference beam, the principal and reference beams having different wavelengths, the target analyte having different absorption coefficients for the different wavelengths, and the reference beam including a mixture of at least two radiations of different wavelengths, having an effective wavelength equal to an intensity-weighted mean of the two component wavelengths, wherein intensities of the periods of radiation are adjusted when the sample is at a first sample fluid state, and at least one effective wavelength of the at least two repetitive periods of radiation is selected to minimize detectable transmission or reflection difference when the sample is at a state different from the first state.

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

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

4. The method of claim 1, further including producing the combined beam by three or more diode lasers.

5. 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 is configured to direct a combined beam of electromagnetic radiation at the sample matrix, the combined beam including at least two repetitive periods of radiation including a principal beam and a reference beam, the principal and reference beams having different wavelengths, the target analyte having different absorption coefficients for the different wavelengths, the reference beam including 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, a sample detector that detects the concentration of the target analyte by measuring radiation reflected to absorbed by the sample matrix, and a controller configured to adjust intensities of the periods of radiation when the sample is at a first sample fluid state, and at least one effective wavelength of the at least two repetitive periods of radiation is selected to minimize detectable transmission or reflection difference when the sample is at a state different from the first state.

6. The system of claim 5, wherein the source of electromagnetic radiation comprises three or more laser diodes.