Infrared Attenuation Profiling for Depth-Selective Substance Detection
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Solution Overview
Problem
Existing methods for detecting substance concentration, such as glucose in human tissue, face challenges in achieving reliable and accurate measurements due to interference from near-surface layers like the stratum corneum, leading to inaccurate depth penetration and saturation issues.
Innovation Solution
A method and device that utilize modulated excitation radiation at multiple wavelengths and frequencies to determine attenuation profiles, allowing for selective measurement depths and subtraction of near-surface interference, using a combination of thermal and pressure wave detection techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If excitation radiation is used to detect substance concentration in tissue, then measurement capability is provided, but interference from near-surface layers (stratum corneum) causes inaccurate measurements
Solution Approach 1:
The patent segments the measurement into multiple depth components by using at least two different modulation frequencies. Each frequency corresponds to a different thermal diffusion length, allowing separation of signals from different tissue depths. This enables the system to isolate and subtract the interfering near-surface layer signal from the desired deeper tissue signal, thereby improving measurement precision.
Solution Approach 2:
The patent introduces a frequency dimension to the measurement process by modulating excitation radiation at multiple different frequencies. This frequency dimension allows the system to encode depth information, where different frequencies correspond to different thermal diffusion lengths and thus different effective measurement depths. By analyzing signals across this frequency dimension, the system can differentiate between near-surface and deeper tissue contributions.
2Measurement precision
If excitation radiation penetrates deep into tissue for accurate measurement, then deeper tissue values are captured, but saturation occurs reducing measurement reliability
Solution Approach 1:
The patent employs dynamic modulation of excitation radiation intensity at different frequencies. By varying the modulation frequency, the system dynamically adjusts the thermal diffusion length, allowing optimization of the measurement depth for each frequency. This dynamic approach enables the system to select optimal frequencies that penetrate to desired depths without causing saturation, thereby maintaining measurement reliability.
Solution Approach 2:
The patent changes the modulation frequency parameter of the excitation radiation to control the thermal diffusion length. By selecting appropriate modulation frequencies, the system can adjust the effective penetration depth of the measurement. This parameter change allows the system to achieve deeper tissue measurement without saturation by using frequencies that produce thermal diffusion lengths matched to the target measurement depth.
3Device complexity
If single frequency modulation is used for detection, then device complexity is reduced, but measurement precision and depth selectivity deteriorate
Solution Approach 1:
The patent implements a multi-functional detection system where a single detection apparatus can measure substance concentration at multiple different depths by processing signals from multiple modulation frequencies. This universal approach allows one system to perform what would otherwise require multiple separate measurement systems, achieving depth-selective capability without proportionally increasing device complexity.
Solution Approach 2:
The patent uses periodic modulation of excitation radiation at multiple frequencies simultaneously or sequentially. This periodic action creates distinct thermal waves at different frequencies that can be detected and separated through frequency analysis. The periodic nature of the modulation allows the system to encode depth information in the frequency domain, enabling depth-selective measurement while using a relatively simple time-multiplexed or frequency-multiplexed detection approach.
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 faster, more reliable, and accurate detection of substance concentrations by minimizing interference from superficial layers, ensuring measurements are not saturated and accurately represent deeper tissue values.
Implementation Method 1
the temperature increase and the generated heat and/or pressure waves resulting from the absorption of excitation radiation in a sample
Implementation Method 2
the temperature increase and the generated heat and/or pressure waves resulting from the absorption of excitation radiation
Data Source
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Figure 5~6
AI summary
The invention relates to a method for detecting a substance, in particular for determining a substance concentration, in a volume (12), especially in a tissue or a sample, in which excitation radiation (18) of different wavelengths is radiated into the volume by means of an excitation source (26) and a reaction of the material in the volume generated by the absorption of the excitation radiation is detected on the basis of a response signal generated as a result of the reaction as a function of the wavelength of the excitation radiation, wherein the intensity of the excitation radiation is modulated with a modulation characteristic.In order to make the measurement even more accurate, it is planned that when determining a substance concentration for the excitation radiation, modulation characteristics are applied at least two, at least three, four, five, seven or ten wavelengths or wavelength ranges, which differ partially or completely for different wavelengths or wavelength ranges.