Method and apparatus for non-invasive measurement of blood sugar level
First Claim
1. A method for non-invasive measurement of blood sugar levels comprising the steps of:
- providing light which is intensity-modulated with a plurality of intensities as well as being wavelength-modulated;
applying the modulated light to an examined portion;
detecting an intensity of reflected light from said examined portion and an intensity of the incident light onto said examined portion for each intensity of said modulated light;
detecting the ratio of an intensity of said reflected light and said incident light;
detecting the rate of change in said ratio with respect to the change in wavelength due to the wavelength modulation;
extracting a derivative spectrum of an absorbance spectrum of glucose in said examined portion, anddetecting the blood sugar level of said examined portion.
1 Assignment
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Accused Products
Abstract
To intensity-modulate laser light periodically wavelength-modulated by and emitted from a wavelength-variable semiconductor laser 11. To separate the laser light into optical paths 13a, 13b with a beam splitter 14 to irradiate an examined location 17 for assessing blood sugar through path 13a. To detect the intensity of transmitted or reflected light from examined location 17 with a first detector 21 and the intensity of laser light passing through path 13b with a second detector 22 to detect the ratio of the former intensity to the latter intensity with a logarithmic ratio amplifier 25. To detect the rate of change in the ratio with respect to the change in wavelength of the wavelength modulation with a lock-in amplifier 26 to obtain a derivative spectral signal of the absorption spectrum of glucose. An arithmetic processor 27 detects blood sugar in the examined location from the derivative spectrum.
180 Citations
5 Claims
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1. A method for non-invasive measurement of blood sugar levels comprising the steps of:
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providing light which is intensity-modulated with a plurality of intensities as well as being wavelength-modulated; applying the modulated light to an examined portion; detecting an intensity of reflected light from said examined portion and an intensity of the incident light onto said examined portion for each intensity of said modulated light; detecting the ratio of an intensity of said reflected light and said incident light; detecting the rate of change in said ratio with respect to the change in wavelength due to the wavelength modulation; extracting a derivative spectrum of an absorbance spectrum of glucose in said examined portion, and detecting the blood sugar level of said examined portion. - View Dependent Claims (2)
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3. An apparatus for non-invasive measurement of blood sugar levels comprising:
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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. - View Dependent Claims (4)
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5. An apparatus for non-invasive measurement of blood sugar levels comprising:
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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.
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Specification