Photoacoustic Coating Thickness Estimation Without Contact Damage
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Solution Overview
Problem
Existing methods for non-destructive coating thickness determination are unsuitable for large-scale industrial applications due to their destructive nature, requirement of contact measurement, or need for sophisticated instrumentation and prior knowledge of the substrate's refractive index, making them impractical for fast-paced industrial environments.
Innovation Solution
A system using a sweep frequency photoacoustic guided wave technique with an intensity modulated Continuous Wave (CW) laser diode generates photoacoustic guided waves, determines frequency spectra, and plots a calibration curve to estimate coating thickness non-destructively, suitable for various substrates and coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional destructive methods (gravimetric mass measurement or cross-sectional microscopy) are used for coating thickness estimation, then measurement precision is improved, but the substrate is damaged and sampling resolution is limited
Solution Approach 1:
The patent replaces mechanical contact-based measurement systems with a photoacoustic wave-based system. An intensity modulated continuous wave laser diode generates photoacoustic guided waves that propagate through the coating layer, and the resonance frequency is determined from the frequency spectrum to calculate coating thickness non-destructively, eliminating mechanical contact and substrate damage while maintaining measurement precision
Solution Approach 2:
The patent utilizes changes in resonance frequency parameters of photoacoustic guided waves as a function of coating thickness. By measuring the resonance frequency shift and using a calibration curve, the coating thickness is determined without physical contact or damage to the substrate, resolving the contradiction between precise measurement and substrate integrity
2Reliability
If contact-based non-destructive methods (ultrasound or eddy current) are used for coating thickness determination, then substrate integrity is maintained, but the methods are unsuitable for large-scale industrial applications and online measurement
Solution Approach 1:
The patent replaces contact-based mechanical measurement systems (ultrasound transducers, eddy current probes) with a non-contact photoacoustic system using laser diodes. The intensity modulated laser generates photoacoustic waves without physical contact, enabling fast, online measurement suitable for large-scale industrial applications while maintaining substrate integrity
Solution Approach 2:
The patent introduces photoacoustic guided waves as an intermediary that can penetrate through the coating layer and interact with the substrate without requiring physical contact. This intermediary wave field enables rapid measurement in industrial settings while preserving substrate integrity, overcoming the limitations of contact-based methods
3Measurement precision
If techniques requiring prior knowledge of refractive index (beta backscatter, X-Ray fluorescence, THz time-domain spectroscopy) are used, then measurement precision may be improved, but the methods become unsuitable for unknown samples and require sophisticated instrumentation
Solution Approach 1:
The patent replaces complex instrumentation systems (X-Ray fluorescence equipment, THz time-domain spectroscopy apparatus) with a simple intensity modulated continuous wave laser diode system. The photoacoustic guided wave method determines coating thickness through resonance frequency measurement without requiring prior knowledge of refractive index or complex instrumentation, reducing device complexity while maintaining precision
Solution Approach 2:
The patent employs a self-calibrating approach where the resonance frequency of the photoacoustic guided waves inherently provides the necessary information for thickness measurement. The system automatically determines the resonance frequency from the frequency spectrum and uses it with a calibration curve to calculate thickness, eliminating the need for external refractive index data or complex instrumentation
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 high-precision, non-destructive estimation of coating thickness suitable for industrial environments, eliminating the need for contact measurement and prior knowledge of substrate properties, and allowing for easy deployment in fast-paced industrial settings.
Implementation Method 1
generating a plurality of photoacoustic guided waves from a plurality of samples by irradiating the plurality of samples by an intensity modulated Continuous Wave (CW) laser diode
Data Source
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AI summary
This disclosure relates to non-destructive estimation of coating layer thickness based on sweep frequency photo acoustic guided wave technique. Coating of a substrate /surface protects it from wear, corrosion and serves the cosmetic aspect, hence making coating technology is an essential part industrial process The existing techniques for coating thickness determination are either destructive or requires a prior knowledge of the refractive index of the surface under investigation or use of sophisticated instrumentation, complicated procedure and harmful radiation during industrial deployment. The disclosure utilizes an intensity modulated Continuous Wave (CW) laser diode to excite a sample thus, making the technique a partially contact based method. Further a calibration curve is plotted by determining a frequency spectrum and resonance frequency. The calibration curve is used for estimation of a coating layer thickness.