Photothermal Analysis of Transparent Samples Using Transparency Factor
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Solution Overview
Problem
Existing photothermal examination methods face challenges in accurately determining thermal material parameters, particularly thermal conductivity and diffusivity, for transparent samples due to complex physical-mathematical models and numerous model parameters, leading to reduced accuracy.
Innovation Solution
A method and device utilizing a pulsed laser or xenon flash lamp to generate an excitation pulse with specific wavelength and duration, combined with infrared detection, and a modified mathematical model that accounts for transparency factors to estimate thermal conductivity and diffusivity with improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional photothermal examination method is used for transparent samples, then the measurement can be performed, but the determination accuracy of thermal material parameters deteriorates due to complex physical-mathematical models with numerous model parameters
Solution Approach 1:
The patent extracts and isolates the transparency factor η as a separate, distinct parameter from the complex system of model parameters. By identifying this single dominant factor that characterizes sample transparency, the method simplifies the evaluation process while maintaining accuracy for transparent samples, directly resolving the contradiction between measurement precision and model complexity
Solution Approach 2:
The patent introduces a transparency factor η that quantifies the degree of sample transparency, transforming the qualitative distinction between opaque and transparent samples into a quantitative parameter. This parameter change allows the use of a unified evaluation approach that adapts to different sample types, improving measurement precision across both opaque and transparent samples while avoiding the need for completely different complex models
2Adaptability or versatility
If the number of model parameters is increased to account for transparency, then the applicability to transparent samples is improved, but the statistical uncertainty and accuracy of parameter determination worsens
Solution Approach 1:
The patent extracts the transparency factor η as a single dominant parameter that captures the essential physics of transparent sample behavior. By focusing on this one key parameter rather than increasing the number of model parameters, the method maintains high statistical accuracy while achieving universal applicability to both opaque and transparent samples
Solution Approach 2:
The patent creates a universal evaluation method that works for both opaque and transparent samples through the introduction of the transparency factor η. When η = 0, the method reduces to the conventional approach for opaque samples; when η > 0, it automatically adapts to transparent samples, providing a single unified solution that improves versatility without sacrificing accuracy
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 precise determination of thermal conductivity and diffusivity for transparent samples by minimizing heat losses and using a novel model that reduces statistical uncertainty, achieving high accuracy in material parameter estimation.
Implementation Method 1
a pulsed laser or a xenon flash lamp to generate an excitation pulse... irradiating a first side ('front') of the sample with a short electromagnetic excitation pulse
Implementation Method 2
detecting thermal radiation emitted from a second side ('back') of the sample opposite the first side as a result of the excitation pulse (as a measure of the temperature on the second side)
Implementation Method 3
an infrared detector to detect heat radiation emitted from a 'detection side', here the back side of the sample
Data Source
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AI summary
The invention proposes a method for the photothermal investigation of a sample (P), comprising: irradiating a first side (16) of the sample (P) with an electromagnetic excitation pulse (18); detecting thermal radiation (26) emitted from a second side (24) of the sample (P) opposite the first side (16) as a result of the excitation pulse (18);Evaluating the detected thermal radiation (26) based on a model defined by the following equations: ∂2T/∂x2=1/α×∂T/∂tfu¨r0 <x<L,t> 0 k×∂T/∂x−h×T=−Et+ηʹ×T0t−TLtfu¨rx=0,t>0 k×∂T/∂x+h×T=−ηʹ×T0t−TLtfu¨rx=L,t>0 Tx0=0fu¨rt=0 where: T denotes the temperature of the sample, L the thickness of the sample, x the position coordinate considered in the thickness direction of the sample, with x=0 at the first side of the sample and x=L at the second side of the sample, t the time, with t=0 at the time of the excitation pulse, E(t) the radiation flux density of the excitation pulse, α the thermal diffusivity of the sample, k the thermal conductivity of the sample, h the heat transfer coefficient at the sample surfaces, η' a "general transparency factor", where a mathematical least squares calculation is performed is used to estimate the aforementioned parameters α, k, h, η' of the model based on a time course of the temperature T(L,t) on the second side (24) of the sample (P) determined from the recorded thermal radiation (26).