Fluorescence Ratio Method for Layer Thickness Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining the thickness of a fluorescent layer are prone to inaccuracies due to fluctuations in excitation radiation power and orientation-dependent optical path lengths, often requiring additional fluorescent dyes that can impair coating functionality and increase costs.
Innovation Solution
A method that uses wavelength-dependent absorption and fluorescence properties of the fluorescent substance to determine layer thickness by detecting fluorescence radiation at two different wavelengths, eliminating the need for additional dyes and accounting for excitation power fluctuations, and evaluating the optical path length of fluorescence radiation to ensure accuracy independent of orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional fluorescent dyes are added to the substance under investigation, then the layer thickness can be determined independently of excitation power fluctuations, but the coating functionality is impaired and material costs increase
Solution Approach 1:
The method uses the intrinsic fluorescence of the fluorescent substance itself without requiring additional dyes. The substance serves its own measurement function by utilizing its inherent wavelength-dependent absorption and fluorescence properties, thereby maintaining coating functionality while enabling accurate thickness measurement.
Solution Approach 2:
The method measures fluorescence at multiple different wavelengths (first and second fluorescence wavelengths) to obtain ratio values that compensate for excitation power fluctuations. By changing the measurement parameter from single-wavelength to multi-wavelength fluorescence detection, the system achieves independence from excitation power variations without adding external dyes.
2Device complexity
If only the optical path length of excitation radiation is evaluated, then the measurement can be simplified, but the result is not identical to the actual layer thickness due to orientation dependence
Solution Approach 1:
Instead of evaluating the optical path length of excitation radiation (which depends on orientation), the method inverts the approach by evaluating the optical path length of fluorescence radiation. Since fluorescence is emitted isotropically in all directions, this reversal provides an orientation-independent measurement that accurately reflects the actual layer thickness.
Solution Approach 2:
The method transitions from measuring along the excitation radiation path (one-dimensional approach dependent on orientation) to measuring fluorescence emission in multiple directions (three-dimensional approach). By detecting fluorescence at different wavelengths and evaluating the optical path length in the fluorescence emission dimension, the system achieves orientation-independent accuracy.
3Measurement precision
If calibration is performed on samples with known layer thickness, then the factors P0, Q, and α can be determined, but the measurement becomes sensitive to excitation power fluctuations over time
Solution Approach 1:
The method uses the ratio of fluorescence powers at different wavelengths as a feedback mechanism to compensate for excitation power fluctuations. The ratio value inherently contains information about the layer thickness while being independent of excitation power variations, providing stable measurements over time without requiring frequent recalibration.
Solution Approach 2:
The method prepares for excitation power fluctuations by measuring fluorescence at multiple wavelengths before any power variation occurs. The ratio of these pre-measured fluorescence powers creates a cushioning effect that compensates for subsequent excitation power changes, ensuring measurement stability without requiring active correction during measurement.
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 provides precise and cost-effective layer thickness measurement without affecting the coating's functionality, as it compensates for excitation power fluctuations and orientation-dependent errors, using intrinsic fluorescence and reducing material costs.
Implementation Method 1
a method for determining a thickness of a layer of a fluorescent substance, wherein the fluorescent substance has a wavelength-dependent absorption coefficient and a wavelength-dependent fluorescence
Implementation Method 2
the absorption coefficient has a value different from zero at least at a first or a second fluorescence wavelength
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
Method for determining the thickness (21) of a layer (20) of a fluorescent substance, wherein the fluorescent substance has a wavelength-dependent absorption coefficient (α) and a wavelength-dependent fluorescence (Pem), wherein the absorption coefficient (α) has a non-zero value at least at a first or a second fluorescence wavelength, and wherein the method comprises the steps A) exciting the layer (20) with electromagnetic excitation radiation (11), B) detecting a first power of fluorescence radiation (31) emitted by the layer (20) at a first fluorescence wavelength, C) detecting a second power of fluorescence radiation (32) emitted by the layer (20) at a second fluorescence wavelength, wherein the first fluorescence wavelength and the second fluorescence wavelength are different from each other and wherein the first and the second power have non-zero values.D) Forming a quotient of the first power and the second power, and E) Deriving the thickness (21) of the layer (20) from the quotient.