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US 4,882,492 AGranted
Non-invasive near infrared measurement of blood analyte concentrations
AssigneeBiotronics Associates, Inc.
InventorKenneth J. Schlager
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AssigneeBiotronics Associates, Inc.
InventorKenneth J. Schlager
Estimating the term…
A non-invasive apparatus and related method for measuring the concentration of glucose or other blood analytes utilizes both diffuse reflected and transmissive infrared absorption measurements and may be applied to either in vitro or in vivo sampling. The apparatus and method utilize non-dispersive correlation spectrometry and apply it to liquid blood serum analysis. Spectrally-modified near infrared light from the sample containing the analyte is split into two beams, one of which is directed through a negative correlation filter which blocks light in the absorption bands for the analyte to be measured, and the other of which is directed through a neutral density filter capable of blocking light equally at all wavelengths in the range of interest. Differencing the light intensity between the two light paths provides a measure proportional to analyte concentration.
A method for the non-invasive measurement of the concentration of a blood analyte comprising the steps of:
Apparatus for the non-invasive measurement of the concentration of a blood analyte comprising a source of modulated near infrared light, means for transmitting the light to a blood analyte source containing the blood analyte and for retransmitting spectrallymodified light from the blood analyte source, means for directing the spectrally-modified light into two beams, a first optical filter in the path of one modified beam having an absorption spectra of the analyte sufficient to block light for the maximum expected concentration of the analyte, a second optical filter in the path of the other modified beam having an absorption spectra sufficient to block light equally at all wavelengths, photosensor means in the path of each beam exiting its respective optical filter for converting the light into a signal representative of the intensity of each beam, means for generating a signal representative of the difference in the intensities of the beams, and means for converting the signal representative of the difference into an of analyte concentration.
Apparatus for non-invasive measurement of glucose concentration in human body tissue comprising a source of modulated near infrared light, means for reflectively transmitting the light to the skin surface of the tissue and retransmitting spectrally-modified light diffusely-reflected from the skin surface, means for receiving and directing the spectrally-modified light into two beam paths, a negative correlation filter in one of the paths having a glucose absorption spectra sufficient to block light for the maximum anticipated concentration of glucose, a neutral density filter in the other path having an absorption spectral sufficient to block light equally at all wavelengths, photosensor means for receiving the filtered beams and for converting the same into signals representative of the intensities of the filtered beams, a lock-in amplifier connected to said photosensor means for generating a signal representative of the difference in the intensities of the filtered beams, and a microprocessor connected to said amplifier for calculating the glucose concentration from the differential signal.
Dependencies are inferred from the claim text.