Back-Scattered Polarimetric Glucose Sensing With Adaptive Filtering
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Solution Overview
Problem
Existing non-invasive glucometers face challenges such as low sensitivity, interference from optical noise and scattering, and inaccurate determination of glucose concentration due to multiple optical paths and depolarization effects, leading to unreliable and complex devices.
Innovation Solution
A non-invasive blood glucose measuring apparatus using a narrow-band wavelength light source, a limiting aperture diaphragm, and an optical detector with a Light Receiving Tube (LRT) to collect back-scattered light, split into orthogonally polarized beams, processed by a computing unit to determine glucose levels through adaptive filtering and calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If polarimetric method is used to measure glucose concentration, then the measurement can be non-invasive and glucose-specific, but the sensitivity is low due to small amount of glucose in blood and strong depolarization effect of tissue
Solution Approach 1:
Instead of measuring transmitted light, the patent measures back-scattered light that has undergone multiple scattering events within the tissue. This inverted approach allows the polarized light to interact more extensively with glucose molecules throughout the tissue volume, enhancing the polarization rotation signal despite the depolarization effects.
Solution Approach 2:
The patent employs periodic modulation of the light source and synchronous detection to distinguish the weak glucose-induced polarization signal from background optical noise. By modulating the light source at a specific frequency and using phase-sensitive detection, the system enhances signal-to-noise ratio and improves measurement sensitivity.
2Length of stationary object
If multiple wavelengths are used to penetrate deeply in tissues, then the measurement depth increases, but the optical paths become different and confuse the outcome
Solution Approach 1:
The patent uses a single narrow-band wavelength rather than multiple wavelengths, changing the spectral parameter to eliminate the problem of different optical paths. This single wavelength approach ensures that all measured light follows the same optical path characteristics, allowing accurate determination of glucose concentration without path-length variations confounding the results.
Solution Approach 2:
By using a single narrow-band wavelength, the patent creates homogeneous measurement conditions where all photons experience similar optical properties. This homogeneity in wavelength ensures uniform interaction with tissue and glucose molecules, eliminating the variability introduced by multi-wavelength approaches.
3Productivity
If two detectors are placed at different locations to measure transmitted light, then the measurement can be performed, but the optical paths to them are considerably different requiring auxiliary circuit compensation
Solution Approach 1:
The patent combines the illumination and detection functions into a single location by measuring back-scattered light. This merging eliminates the need for spatially separated detectors and their associated different optical paths, thereby removing the requirement for complex auxiliary compensation circuits while maintaining measurement capability.
Solution Approach 2:
The back-scattered light acts as an intermediary that carries glucose concentration information from deep within the tissue back to the detector at the surface. This intermediary approach allows measurement of deep tissue glucose without requiring detectors at multiple locations, simplifying the device architecture.
4Measurement precision
If conventional polarimetric glucometer is designed, then non-invasive measurement is achieved, but the device is complex and lacks repeatability due to patient condition and sensor location variations
Solution Approach 1:
The system performs self-calibration by using the back-scattered light path itself as the reference. The polarization rotation measured in back-scattered mode inherently accounts for tissue-specific optical properties, eliminating the need for external calibration procedures and making the device adaptable to different patients and measurement locations without complex setup.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus provides accurate, reliable, and fast glucose measurements without specific body part limitations, capable of long-term monitoring and instantaneous detection with minimal delay, overcoming issues of attenuation and depolarization.
Implementation Method 1
the light beam can penetrate deeply in living tissues, depending on the light power and wavelength
Implementation Method 2
an output polarizer, for polarizing said emitted narrow-band wavelength light beam into a single linearly polarized light beam
Implementation Method 3
a limiting aperture diaphragm, for irradiating the linearly polarized light into said object of measurement, in orthogonally to the illuminated surface
Implementation Method 4
which is back-scattered from the object of measurement
Implementation Method 5
which has propagated through said blood vessel, which serves as an optical waveguide, between said light-emitting source and said LRT
Implementation Method 6
a beam splitter, for splitting said collected back-scattered light from the object of measurement, into two separate light beams
Implementation Method 7
at least two polarizers, for polarizing said two separate light beams into two orthogonally polarized beams
Implementation Method 8
at least two detector-amplifiers for detecting and amplifying the intensities of said two orthogonally polarized beams
Implementation Method 9
said computing unit comprises an adaptive filter for enhancing the cardiac pulse pulsatile waveform, affected by noise and respiration trend
Implementation Method 10
The dissolved sugar, in the blood, rotates the linearly polarized light clockwise from its original polarization direction due to the sugar optical activity
Data Source
AI summary
The present invention relates to a non-invasive blood glucose measuring apparatus, for measuring the glucose level in an object of measurement, comprising: (a) an irradiation source, for irradiating a narrow-band wavelength light into said object of measurement containing a blood vessel; (b) an optical detector, for collecting and processing some of the light, irradiated by said irradiating source, which is back-scattered from the object of measurement, (c) sampling means, for sampling said orthogonally polarized beams, provided by said detector-amplifiers, for converting the data of said orthogonally polarized beams into digital codes; and (d) a computing unit, wherein said computing unit comprises an adaptive filter for enhancing the cardiac pulse pulsatile waveform, and wherein said computing unit computes the glucose level, in said object of measurement, by averaging of said sampled codes.