Blood glucose measurement with multiple quantum cascade lasers using hollow-optical fiber-based ATR spectroscopy

For non-invasive blood glucose measurement, a measurement system based on mid-infrared ATR spectroscopy equipped with a combination of a QCL as a light source and a hollow-optical fiber as a beam delivery medium is developed. Firstly the measurement sensitivity of the system is evaluated by using glucose solutions and the result shows a significant correlation between optical absorbance and solution concentration. It is also confirmed that the system has a sensitivity that is enough for blood glucose measurement. Then optical absorption of human lips in the mid-infrared wavelength region is measured using a QCL with a wavenumber of 1080 cm(-1) where human tissue exhibits strong absorption of glucose and its metabolites. As a result, the measured absorption follows the change of blood glucose well with a time delay of around 10 minutes and correlation factor between the absorbance and the blood glucose level is 0.42.