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

Claim 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.

Claim 4

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.

Claim 5

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.