Non-invasive measurement of blood glucose by attenuated total reflection spectroscopy with fixed-wavelength quantum cascade lasers

For non-invasive blood glucose measurement, a measurement system based on mid-infrared ATR spectroscopy equipped with a combination of quantum cascade lasers (QCLs) as light sources and hollow-optical fibers as a beam delivery media is developed. Firstly the optical absorption of human lips in the mid-infrared wavelength region is measured using FT-IR. The spectrum shows the wavenumber of 1152 cm"1 exhibits strong absorption of glucose. Then we also confirmed that there is no absorption at the wavenumber of 1186 cm"1 from the spectrum of glucose solution. Finally we measured absorption of human lips using the QCL with these wavelengths. As a result, the measured differential absorption follows the change of blood glucose well and the correlation factor between the absorbance and the blood glucose level is 0.55.