Method and apparatus for non-invasive measurement of blood sugar level

An apparatus for non-invasive measurement of blood sugar levels comprising:

• a wavelength-modulated light generator for generating a wavelength-modulated light;
• an intensity-modulator for intensity-modulating the wavelength-modulated light output from said wavelength-modulated light generator with a plurality of intensities;
• a beam splitter for separating the optical path of the wavelength-modulated and intensity-modulated light emitted from said intensity modulator into two optical paths;
• an optical collector for collecting the light passing along one of the two optical paths separated by said beam splitter, being incident on an examined location for assessing the blood sugar level, and being reflected therefrom;
• a first optical detector for detecting an intensity of the light collected by said optical collector;
• a second optical detector for detecting an intensity of the light passing along the other optical path separated by said beam splitter;
• a ratio detector for detecting the ratio of the output of said first optical detector to the output of said second optical detector;
• a derivative spectral signal detector for receiving a ratio signal from said ratio detector and for detecting the rate of change in said ratio signal with respect to the change in wavelength due to the wavelength modulation to detect a derivative spectral signal of an absorbance spectrum of glucose in said examined portion;
• an arithmetic means for calculating the blood sugar level in said examined location based on the derivative spectral signal detected by said derivative spectral signal detector.

An apparatus for non-invasive measurement of blood sugar levels comprising:

• a wavelength-variable light source for wavelength-modulated light;
• an attenuator for periodically varying the intensity of the light output from the light source;
• a beam splitter for separating light output from the attenuator into a reference light beam and a measuring light beam;
• an integrating sphere for collecting light reflected from an examined portion of skin in which the blood sugar level is to be measured, the reflected light caused by the measuring light beam being projected on the examined portion of skin;
• a first detector for detecting the intensity of the light collected by the integrating sphere;
• a second detector for detecting the intensity of the reference light beam;
• first and second amplifiers for respectively amplifying outputs of said first and second detectors;
• a logarithmic ratio amplifier for receiving outputs from said first and second amplifiers and for outputting a logarithm of a ratio between outputs of the first and second amplifiers;
• a lock-in amplifier for receiving an output from said logarithmic ratio amplifier and for detecting a derivative spectral signal of a glucose absorbance spectrum for the examined portion from a rate of change of the output of the logarithmic ratio amplifier with respect to a change in wavelength;
• a processing means for receiving an output from said lock-in amplifier and for calculating a blood sugar level in the examined portion by processing the derivative spectral signal detected by said lock-in amplifier.