Paint Layer Thickness Measurement Using Optical Coherence Tomography
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Solution Overview
Problem
Current methods for determining paint layer thickness on vehicle parts, especially those made of plastic, are inadequate as they require electrical or magnetic conductivity and can only measure total layer thickness, failing to provide detailed thickness of each layer necessary for quality control and radar calibration.
Innovation Solution
A non-contact, non-destructive method using optical coherence tomography with visible light to determine layer thicknesses of paint layers, combined with dielectric, capacitive, or magneto-inductive measurements, allowing for the determination of each layer thickness even on non-conductive materials like plastic, by employing multiple radiation sources and considering refractive indices to account for color and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive or magnetic inductive thickness measurement is used, then total layer thickness can be determined, but the method requires electrical or magnetic conductivity and cannot measure individual layers
Solution Approach 1:
The patent segments the measurement task into two parts: using optical coherence tomography to measure individual transparent/semi-transparent paint layers, and using capacitive/magnetic inductive methods to measure the total thickness. This segmentation allows each method to be used where it is most effective, resolving the contradiction between total thickness measurement capability and individual layer measurement capability.
Solution Approach 2:
The patent introduces an intermediary calculation step where the thickness of the first paint layer is determined by subtracting the sum of subsequent layer thicknesses (measured by OCT) from the total layer thickness (measured by capacitive/magnetic inductive method). This intermediary calculation enables indirect measurement of the first layer without requiring it to be transparent or conductive.
2Measurement precision
If optical coherence tomography with visible light is used, then individual transparent layer thickness can be determined, but it cannot penetrate opaque paint layers
Solution Approach 1:
The patent segments the paint layer structure into transparent/semi-transparent layers (measurable by OCT) and opaque layers (measured by subtraction from total thickness). This segmentation allows the system to handle mixed transparent/opaque coatings by applying appropriate measurement methods to each segment.
Solution Approach 2:
The patent uses the total layer thickness measurement (obtained via capacitive or magnetic inductive methods) as an intermediary value. By subtracting the OCT-measured thickness of transparent layers from this total, the system indirectly determines the thickness of opaque layers that cannot be directly measured by optical methods.
3Ease of manufacture
If only total layer thickness is measured, then measurement process is simple, but individual layer thicknesses cannot be determined for quality control
Solution Approach 1:
The patent segments the information extraction process: the OCT system provides individual thickness data for transparent layers, while the capacitive/magnetic inductive system provides total thickness. This segmented information gathering preserves all necessary quality control data while maintaining relatively simple measurement procedures.
Solution Approach 2:
The patent uses mathematical calculation (subtraction) as an intermediary process to derive individual layer thickness information from combined measurements. This allows full layer breakdown information to be obtained without requiring complex multi-step measurement procedures for each layer.
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, contact-free measurement of each paint layer thickness, improving quality control and eliminating the need for individual radar sensor calibration, while being suitable for both transparent and opaque layers, including metallic coatings.
Implementation Method 1
The device has at least one radiation source for providing electromagnetic radiation and the electromagnetic radiation provides a wavelength of 100 to 15 × 10³ nm and in particular 380 to 800 nm for performing optical coherence tomography
Implementation Method 2
determining the total coating thickness of the coating layers by means of a dielectric, capacitive, or magnetic inductive coating thickness measurement
Implementation Method 3
determining the total coating thickness of the coating layers by means of a dielectric, capacitive, or magnetic inductive coating thickness measurement
Implementation Method 4
determining the coating thicknesses of all further coating layers by means of optical coherence tomography
Data Source
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AI summary
The present invention relates to methods for non-contact and non-destructive determination of the layer thicknesses (d) of paint layers of vehicle parts (12), comprising the following steps: - providing a vehicle part (12) with a first paint layer (26) applied to the vehicle part (12), which has a first layer thickness (d1), and at least one further paint layer (28, 32, 36) applied to the first paint layer (26), which has a further layer thickness (d2, d3, d4), wherein at least the further paint layer (28, 32, 36) or one of the further paint layers (28, 32, 36) is optically opaque, - determining the layer thickness (d2, d3, d4) of at least the further paint layer (28, 32, 36) by means of a device (10) configured for performing optical coherence tomography,wherein the device (10) comprises at least one radiation source (14) for providing electromagnetic radiation and the electromagnetic radiation provides a wavelength (λ) of 100 to 15 × 10³ nm and in particular 380 to 800 nm. Furthermore, the invention relates to a device (10) for the non-contact and non-destructive determination of the layer thicknesses of paint layers (26, 28, 32, 36) of vehicle parts (12), which is configured to carry out such a method.