Method for obtaining a ratio measurement for correcting common path variations in intensity in fiber optic sensors

• US 4,792,689 A
• Filed: 11/24/1987
• Issued: 12/20/1988
• Est. Priority Date: 11/12/1985
• Status: Expired due to Fees

• Current Assignee: United States Department Of Health And Human Services
• Original Assignee: United States Department Of Health And Human Services
• Inventors: Peterson, John I.
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US07/129,387
• Time in Patent Office: 392 Days
• Field of Search: 356/317, 356/318, 356/417, 356/445, 250/227, 250/458.1, 250/459.1, 250/461.1, 250/461.2, 422/57, 422/68, 436/172
• US Class Current: 250/458.1
• CPC Class Codes: G01N 2021/7786 Fluorescence
• CPC Class Codes: G01N 21/19 Dichroism
• CPC Class Codes: G01N 21/6428 Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" in vivo A61B5/00; immunoassay G01N33/53
• CPC Class Codes: G01N 21/643 non-biological material
• CPC Class Codes: G01N 21/76 Chemiluminescence; Bioluminescence
• CPC Class Codes: G01N 21/7703 using reagent-clad optical fibres or optical waveguides using measurement of total internal reflection or attenuated total reflection G01N21/552; optical fibres or waveguides per se G02B

Abstract

A method for correcting common path variations in intensity in fiber optic chemical sensing devices uses a device for spatially separating light of different wavelength regions and a dye system selected so that light passing back to a measuring system along the fiber optic sensor consists of two wavelength regions. The first wavelength region varies with the concentration of analyte, and the other wavelength region is insensitive to the concentration of analyte.

Claims

1. A fiber optic sensing system for measuring the concentration of an analyte, said system comprising:

an otpical fiber having a first end and a second end;

a light source for illuminating said optical fiber, at said first end or between said first and second ends, with illumination light of a first wavelength region directed toward said second end of said optical fiber;

a sensor optically connected to said second end of said optical fiber, said sensor including a mixture of a first and a second indicator dye, said first indicator dye, when illuminated by said light of said first wavelength region, emitting light of a second wavelength region at an intensity sensitive to the concentration of the analyte to be measured, said second indicator dye, when illuminated by said light of said first wavelength region, emitting light of a third wavelength region at an intensity insensitive to the concentration of the analyte to be measured, said first, second and third wavelength regions differing from each other and being essentially non-overlapping;

means for spatially separating light of said first wavelength region reflected by said sensor into second end of said optical fiber from said light of said second and third wavelength regions emitted by said indicator dyes;

means for measuring the ratio of the intensities of said second and third wavelength regions with respect to each other, thereby producing a corrected signal corresponding to the concentration of hhe analyte to be measured, said measuring means including means for spatially separating light of said second and third wavelength regions from each other.

2. The device of claim 1, wherein the means for spatially separating light of said second and third wavelength regions from each other is a dichroic mirror.

3. A method for correcting common path variations in intensity in fiber optic chemical sensing devices, comprising the steps of:

admitting an analyte into a sensor of an optical fiber having a first end an a second end;

illuminating said optical fiber, at said first end or between said first and second ends, with illumination light of a first wavelength region directed toward a second end of said optical fiber, said sensor being optically connected to said second end of said optical fiber, said sensor including a mixture of a first and a second indicator dye, said first indicator dye, when illuminated by said light of said first wavelength region, emitting light of a second wavelength region at an intensity sensitive to the concentration of said analyte, said second indicator dye, when illuminated by said light of said first wavelength region, emitting light of a third wavelength region at an intensity insensitive to the concentration of said analyte, said first, second and third wavelength regions differing from each other and being essentially non-overlapping;

spatially separating light of said first wavelength region reflected by said sensor from light of said second and third wavelength regions emitted by said indicator dyes;

spatially separating light of said second and third wavelength regions from each other;

measuring the ratio of the intensities of said second and third wavelength regions with respect to each other, thereby producing a corrected signal corresponding to the concentration of the analyte to be measured.

4. The method of claim 3, wherein the indicator dye mixture includes a dye selected from the group consisting of fluorescent dyes and phosphorescent dyes.

5. The method of claim 4, wherein the indicator dyes are fluorescent.

6. The method of claim 4, wherein the indicator dyes are phosphorescent.

7. The method of claim 3, wherein the indicator dye mixture comprises a pair of dyes which both absorb in the blue region, one dye emits green light and the other dye emits red light.

8. The method of claim 3, wherein dichronic mirror means are used for spatially separating light of different wavelength regions from each other.