Optical Path Length Correction for Non-Invasive Substance Measurement
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Solution Overview
Problem
Non-invasive measurement of scattering-absorption bodies, such as hemoglobin in blood, is impaired by intervening tissue like fat, which affects measurement precision due to variability in optical path length, requiring complex pre-measurement of fat thickness and lack of clear relationship between fat thickness and mean optical path length.
Innovation Solution
A method and device that corrects measurement results by establishing a correlation between mean optical path length and intervening tissue thickness, allowing for the exclusion of intervening tissue influence, using a device with light incident and detection means, signal processing, and calculation units to estimate intervening tissue thickness and correct substance concentration measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light is used to measure substance concentration in a scattering-absorption body non-invasively, then measurement of hemoglobin in blood is enabled, but measurement precision deteriorates due to variability in optical path length caused by intervening tissue thickness
Solution Approach 1:
The patent introduces an intermediary parameter (mean optical path length) that mediates between the light measurement and the substance concentration calculation. By using the temporal profile of detected light to calculate mean optical path length, the system indirectly accounts for intervening tissue effects without requiring direct measurement of tissue thickness, thus maintaining measurement precision while avoiding complex additional measurement devices
Solution Approach 2:
The patent replaces mechanical measurement methods (such as separate fat thickness measurement devices) with an optical-based calculation approach. By substituting the mechanical measurement system with an optical temporal profile analysis system, the patent achieves the same correction function while simplifying the overall device complexity
2Measurement precision
If separate fat thickness measurement is performed beforehand to correct measurement results, then measurement precision is improved, but the measurement process becomes complex and time-consuming
Solution Approach 1:
The patent merges the substance concentration measurement process with the optical path length calculation process. By simultaneously obtaining the temporal profile of detected light and calculating the mean optical path length from the same light measurement data, the system eliminates the need for separate fat thickness measurement steps, thereby reducing measurement time while maintaining precision through correction
3Measurement precision
If the thickness of intervening tissue increases, then the proportion of optical path length through intervening tissue increases, but the partial optical path length through the region to be measured decreases, leading to smaller measured values
Solution Approach 1:
The patent implements a feedback mechanism where the calculated mean optical path length is used to correct the measured substance concentration values. The system continuously adjusts the measurement results based on the optical path length information derived from the temporal profile, automatically compensating for varying intervening tissue thickness effects without requiring manual intervention or complex operational adjustments
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
Enables accurate measurement of substance concentration in the region of interest by accounting for intervening tissue thickness, improving measurement precision and simplifying the measurement process by correlating mean optical path length with tissue thickness, thus providing reliable results without the need for separate fat thickness measurement.
Implementation Method 1
pulsed light to irradiate, at a light incidence position, a scattering-absorption body... The pulsed light, while being scattered, reaches then a light detecting position
Implementation Method 2
scattering-absorption body that comprises a region to be measured... variation amount of the absorption coefficient
Data Source
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AI summary
Light P of a predetermined wavelength irradiates one light incident position I set on the surface Ba of a scattering-absorption body B. The light P that propagates through the interior of the scattering-absorption body B is detected at one light detecting position D set on the surface Ba of the scattering-absorption body B, to yield a light detection signal. On the basis of this light detection signal, a temporal profile of the light intensity of the detected light is acquired, and on the basis of the temporal profile, an mean optical path length L of the light P in the interior of the scattering-absorption body B and information relating to the amount of substance to be measured in a region to be measured B1 are calculated. The information relating to the amount of substance to be measured is corrected on the basis of the mean optical path length L, such that the longer the mean optical path length L, the greater the amount of substance to be measured is. The method allows obtaining measurement results, exhibiting no influence of intervening tissue, to be obtained in accordance with a simple method.