Non-invasive Multilayer Medium Analysis via Adaptive Photoacoustic Detection
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Solution Overview
Problem
Non-invasive sensors based on photoacoustic or photothermal detection face challenges in accurately measuring parameters of interest in multilayer media, particularly when the structure of the target medium changes over time, due to interference phenomena and the need for precise wavelength and modulation frequency selection, which complicates the interpretation of thermal or acoustic signals.
Innovation Solution
A process using a tunable light source and a detection system with a signal processing module and adaptation module that employs an abacus of correlation cases to determine the sense of variation of parameters by analyzing the amplitude and phase of detected waves, allowing for adaptive irradiation configurations without prior knowledge of the medium's structure, and enabling continuous monitoring with reduced power and time consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photoacoustic or photothermal detection is used to measure parameters in multilayer media, then non-invasive sensing capability is achieved, but interference phenomena occur when the medium structure changes over time, reducing measurement accuracy
Solution Approach 1:
The patent changes the modulation frequency parameter of the laser to move away from thermal wave interference conditions. By detecting the derivative of the photoacoustic signal with respect to modulation frequency, the system identifies frequencies where interference effects are minimized, thereby improving measurement accuracy while maintaining non-invasive sensing capability
Solution Approach 2:
The system uses real-time detection of photoacoustic signals to feedback on the actual thermal wave interference conditions in the multilayer medium. Based on this feedback, the modulation frequency is dynamically adjusted to optimal values that minimize interference, ensuring continuous high-accuracy measurements even as the medium structure evolves
2Measurement precision
If multiple wavelengths and modulation frequencies are tested to find optimal measurement conditions, then measurement accuracy improves, but the time and power consumption increase
Solution Approach 1:
The patent performs a preliminary scan to detect the derivative of the photoacoustic signal with respect to modulation frequency. This preliminary action identifies the optimal modulation frequency range where interference effects are minimal, allowing subsequent measurements to be performed quickly at these pre-identified optimal frequencies without requiring exhaustive testing of multiple frequencies
Solution Approach 2:
Instead of testing all possible wavelengths and frequencies, the system performs a partial search by detecting the signal derivative with respect to frequency. This partial action (measuring only the frequency derivative) provides sufficient information to identify optimal conditions, avoiding the excessive time and power consumption of comprehensive multi-parameter optimization
3Measurement precision
If the modulation frequency is adjusted to account for changes in target structure, then measurement accuracy is maintained, but the device complexity increases
Solution Approach 1:
The system uses the photoacoustic detection system itself to automatically identify optimal modulation frequencies by detecting the derivative of the signal with respect to frequency. The same hardware components (laser, detector, signal processing electronics) serve both the primary measurement function and the frequency optimization function, eliminating the need for additional complex calibration equipment or external characterization systems
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
This approach enables accurate and reliable determination of parameter variations in multilayer media over time, reducing the need for multiple measurements and improving the confidence in non-invasive sensing, while allowing for continuous monitoring and alert systems without extensive prior calibration.
Implementation Method 1
The laser beam is absorbed by the target over a characteristic length that depends on the structure of the target. The absorption of light energy leads to local heating of the target.
Implementation Method 2
The absorption of light energy leads to local heating of the target. In response to this heating, a thermal wave of frequency equal to the modulation frequency of the laser is generated in the target.
Implementation Method 3
Photoacoustic detection exploits the fact that the thermal wave is associated with a pressure wave having a frequency identical to the modulation frequency of the laser.
Data Source
Figure 1~2
Figure 3a
Figure 3b
AI summary
A process for analyzing at least one parameter of interest in a target multilayer medium (2) with a non-invasive sensor based on photoacoustic or photothermal detection, comprising: a) providing a non-invasive sensor comprising a light source, a detection cell, a signal processing module, an adaptation module comprising a processor and a memory storing an abacus of correlation cases, the abacus of correlation cases comprising, for each of a plurality of pairs comprising one of a plurality of model configuration of the target multilayer medium and one of a plurality of irradiation configuration of the light source, at least one associated correlation case b) determining a particular model configuration of the target multilayer medium; c) determining a particular irradiation configuration for subsequent irradiation based on the abacus of correlation cases and on the particular model configuration ; d) performing a plurality of irradiations of the target multilayer medium and determining a respective amplitude and a respective phase of said signal at at least one wavelength and at least one respective associated modulation frequency; e) calculating the third sign of a correlation case based on the determined respective amplitudes and phases; f) determining a correlation case based on the abacus of correlation cases and the respective calculated third sign; g) determining the sense of variation of at least one parameter of interest with an amplitude and/or a phase of the thermal or acoustic signal based on the at least one associated correlation case determined at f).