NON-INVASIVE BLOOD ANALYSIS BY NEAR INFRARED ABSORPTION MEASUREMENTS USING TWO CLOSELY SPACED WAVELENGTHS

摘要

Systems and methods for non-invasive blood analysis are disclosed in which blood is illuminated at a plurality of discrete wavelengths selected from the near infrared spectrum. Measurements of the intensity of transmitted or reflected light at such wavelengths are taken, and an analysis of transmittance or reflectance ratios for various wavelengths is performed. Changes in the ratios can be correlated with the specific near infrared (IR) absorption peak for the analyte which varies with concentration of the analyte (the data wavelength) and a second (reference) wavelength being sufficiently removed from the first so that measurements of light absorption at this second wavelength are relatively insensitive to the concentration of the analyte and yet the second wavelength is sufficiently close to the first wavelength to minimize interference from scattering effects and the like. Typically, the window bracketing these closely spaced wavelengths will be less than about 300 nm and preferably less than about 60 nm wide and, in some instances, more preferably less than about 30 nm wide.