Diagnosis and Healthcare Monitoring Systems Based on Infrared Spectroscopy

Abstract

Bio-molecules show strong optical absorption in the mid-infrared region of 2.5-25 micron wavelength and therefore, by analyzing the absorption spectrum (so-called “fingerprint spectrum”), a variety of non-invasive diagnoses will be possible. In this paper, firstly a blood-glucose measurement system based on Fourier-infrared spectrometry (FT-IR) is introduced. In this system, by using a flexible optical fiber, optical absorption spectra of lip mucosa that show relatively strong absorption of glucose are measured by touching the lips on a prism. By measurement using the human lips, it is shown that the system can measure blood glucose with a measurement error of less than 20％. Next, a blood glucose measurement system using quantum cascade lasers (QCLs) oscillated in the mid-infrared region is introduced for constructing a compact and low-cost system. By using the QCL-based system, it is shown that the differential absorption between two wavelengths that were chosen based on optical spectra taken by the FT-IR-based system exhibits a high correlation with blood glucose level.