Confocal Microscope Layer Thickness Measurement Interference Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional confocal microscopy methods struggle to precisely measure the thickness of thin layers due to overlapping intensity bands, which leads to erroneous results due to interference effects, making it challenging to accurately determine layer thicknesses less than 2 μm.
Innovation Solution
A confocal microscope equipped with a mathematical model that accounts for interference effects between overlapping intensity bands, using wavelength and numerical aperture dependencies to accurately determine layer thickness by adjusting fit functions based on measurement data from different wavelengths and pinhole settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional confocal microscopy methods are used to measure thin layers, then the measurement process is simple, but the measurement precision deteriorates due to overlapping intensity bands causing erroneous results
Solution Approach 1:
The patent applies parameter changes by varying the numerical aperture of the objective lens and using multiple wavelengths of illumination light. By changing these parameters, the system captures intensity bands under different optical conditions, which when processed through the mathematical model, enables accurate separation and measurement of thin layers that would otherwise be indistinguishable due to overlapping bands.
Solution Approach 2:
The patent introduces a mathematical model as an intermediary that processes the confocal intensity measurements. This model accounts for interference effects and the relationship between numerical aperture, wavelength, and intensity band positions. The mathematical model acts as a mediator that translates raw confocal data into accurate layer thickness measurements by compensating for the overlapping intensity band problem.
2Measurement precision
If the numerical aperture is increased to improve resolution, then the measurement precision improves, but the interference effects between overlapping intensity bands increase causing measurement errors
Solution Approach 1:
The patent uses feedback by iteratively adjusting the mathematical model parameters to match the observed intensity band positions. The model predicts where intensity bands should appear based on the numerical aperture and wavelength, compares this with actual measurements, and refines the layer thickness determination accordingly. This feedback loop enables accurate measurement despite interference effects.
Solution Approach 2:
The patent changes the numerical aperture parameter to optimize the balance between resolution and interference effects. By using variable numerical aperture settings and incorporating this parameter into the mathematical model, the system can select optimal aperture values that provide sufficient resolution while minimizing interference-induced measurement errors.
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 measurement of thin layer thicknesses by correcting for interference-induced shifts in intensity band positions, providing accurate layer thickness determination even for layers less than 2 μm thick, thereby improving the accuracy of confocal microscopy measurements.
Implementation Method 1
A confocal microscope equipped with a mathematical model that accounts for interference effects between overlapping intensity bands, using wavelength and numerical aperture dependencies to accurately determine layer thickness
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A confocal microscope for measuring layer thickness comprises: optical elements for guiding and focusing illumination light onto a sample; a focus adjustment device with which a relative adjustment between a focus position of the illumination light and a sample position is made along an optical axis of the confocal microscope; a confocally arranged light measuring device with which measurement signals for different settings of the focus adjustment device can be recorded; an evaluation device for determining a layer thickness of the sample, for which the evaluation device determines intensity band positions of at least two intensity bands from a measurement curve recorded by the light measuring device, which indicates a measured light intensity as a function of the focus position, and infers a layer thickness based on a position difference between the intensity band positions.The evaluation device is designed to infer the layer thickness using a mathematical model which describes a dependence of the intensity band positions on at least one wavelength of light and the layer thickness for overlapping intensity bands, taking into account interference of the illumination light at the layer.