Multi-Layer Thickness Measurement via Spectral Domain OCT
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Solution Overview
Problem
Current methods for assessing multi-layer structures, such as tear films and industrial films, face limitations in simultaneously measuring the thickness of individual layers with high precision, particularly in the context of Dry Eye Disease where non-invasive techniques are needed to understand tear film dynamics effectively.
Innovation Solution
The integration of ultra-high axial resolution optical coherence tomography (OCT) with statistical decision theory (SDT) enables simultaneous estimation of the thicknesses of the lipid and aqueous layers in tear films, using a customized OCT system and a maximum-likelihood estimator to achieve nanometer-scale precision, addressing the limitations of conventional Fourier-domain OCT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Fourier-domain OCT with peak detection is used, then the measurement process is simple, but the axial resolution is limited to micron scale and cannot simultaneously measure both lipid and aqueous layers with high precision
Solution Approach 1:
The patent changes the fundamental parameter of axial resolution by transitioning from conventional Fourier-domain OCT to spectral domain OCT with a customized spectrometer, achieving ultra-high axial resolution at the nanometer scale. This parameter change enables simultaneous measurement of both lipid and aqueous layers with precision previously unattainable by conventional methods.
Solution Approach 2:
The patent replaces the conventional peak detection algorithm in Fourier space with a statistical decision theory-based spectrum fitting approach that operates directly on raw spectral data. This substitution of the measurement algorithm enables more precise thickness estimation by utilizing the full spectral information rather than relying on peak positions in the Fourier domain.
2Measurement precision
If spectral domain OCT with statistical decision theory is used, then nanometer-scale precision is achieved for simultaneous lipid and aqueous layer measurement, but the system complexity and computational requirements increase
Solution Approach 1:
The statistical decision theory framework automatically optimizes the spectrum fitting process by evaluating multiple possible layer configurations and selecting the most probable thickness values based on the measured spectral data. This self-service approach eliminates the need for manual calibration or complex post-processing, as the algorithm independently determines the optimal thickness parameters that best fit the observed interference spectrum.
3Productivity
If conventional OCT methods are used, then the measurement process is straightforward, but the ability to spatially quantify tear film dynamics and provide simultaneous measurements of lipid and aqueous layers is lacking
Solution Approach 1:
The patent segments the tear film into distinct lipid and aqueous layers by analyzing the spectral interference patterns from each interface. The statistical decision theory approach separately estimates the thickness of each layer by fitting the spectral data to a multi-layer model, enabling simultaneous independent measurement of both layers with nanometer-scale precision rather than measuring only the total combined thickness.
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 a two orders of magnitude improvement in precision for the lipid layer thickness measurement and achieves nanometer-scale accuracy for both the lipid and aqueous layers, enabling better management of Dry Eye Disease and applicable to other multi-layer structures like industrial films and biomedical samples.
Implementation Method 1
directing light from a light source of a low coherence interferometry (LCI) component to a multi-layer structure... collecting spectrally dispersed light at a detection module of the low coherence interferometry component, the collected light including back-reflected or back-scattered light
Implementation Method 2
collecting spectrally dispersed light at a detection module... generating a spectrum array of spectral intensity values derived from the light collected at the detection module
Data Source
AI summary
Systems and methods for assessing multi-layer structures in which a spectrum array is generated from low coherence interferometry and input into a statistical estimator, which determines the thickness and layer number based on the inputted spectrum and other information, including information about a source intensity noise, Poisson noise, and dark noise associated with the low coherence interferometry.