OCT Image Rectification via Iterative Refractive Index Determination
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Solution Overview
Problem
Optical coherence tomography (OCT) images of elongated objects are distorted due to refractive index differences between object layers and air, leading to inaccurate reconstructions, as prior methods rely on inaccurate pre-estimated refractive indices that change over time.
Innovation Solution
A method that captures an elongated object from multiple orientations, determines refractive indices of individual layers by analyzing spatial reconstruction deviations, and calculates a rectified overall reconstruction image using these indices, allowing for low-distortion or distortion-free image reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fixed pre-estimated refractive index values are used for image rectification, then the rectification process can be performed, but the reconstructed images remain distorted due to inaccuracy of the estimates
Solution Approach 1:
The patent implements a feedback mechanism where the system iteratively adjusts the refractive index values based on the coherence of features across multiple discrete tomographic reconstructions. The process continuously refines the refractive index estimates until the reconstructed images from different orientations show consistent structural features, thereby achieving accurate rectification without requiring prior knowledge of the exact refractive indices.
Solution Approach 2:
The system performs preliminary discrete tomographic reconstructions using initially estimated refractive index values before the final rectification step. These preliminary reconstructions are used to analyze feature coherence and guide the subsequent refinement of refractive index values, ensuring that the final rectified image is free from distortion.
2Productivity
If discrete tomography with few orientations is used, then the measurement process is faster and simpler, but the reconstructed images show distortion due to refraction effects
Solution Approach 1:
The patent changes the refractive index parameter iteratively based on the coherence analysis of features across multiple discrete orientations. By adjusting this critical parameter and re-evaluating the reconstructions, the system achieves accurate image rectification while maintaining the efficiency benefits of discrete tomography with only a few measurement orientations.
Solution Approach 2:
The system dynamically adjusts the refractive index values during the rectification process based on real-time coherence analysis. This dynamic adaptation allows the system to achieve high reconstruction accuracy without requiring a large number of discrete orientations, thus maintaining measurement speed while improving precision.
3Loss of information
If multiple discrete orientations are measured, then more information is available for rectification, but the measurement time and complexity increase
Solution Approach 1:
The patent replaces the need for continuous tomographic measurement (which would require many orientations and significant time) with a discrete measurement approach enhanced by computational coherence analysis. By using algorithms to analyze feature consistency across a few orientations, the system extracts maximum information from minimal measurements, avoiding the time loss associated with acquiring data from many orientations.
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 the generation of low-distortion or distortion-free reconstruction images by accurately determining refractive indices, which can be continuously updated, improving the precision of object cross-section representation in OCT imaging.
Implementation Method 1
a broadband light signal with little coherence length is temporally (in an OCT method in the time domain, the time-domain, (TD-OCT) as well as in the frequency domain with the aid of a spectrometer, the frequency domain, (FT-OCT)) or an in the wavelength time-varying monochromatic light signal (in an OCT method in the frequency domain with a wavelength-controlled source, the swept source (SS-OCT)) is split in a beam splitter into at least two partial signals
Implementation Method 2
The first partial signal (measuring signal) reflected by the object to be captured is superimposed with the reference signal in an interferometer, whereby an interference signal is generated
Implementation Method 3
the result of the measurement along the ray path appears straight in the OCT image, although in reality the ray path, due to refraction at different layer boundaries or layer transitions of the object with different refractive indices, experiences deflections in each case
Data Source
AI summary
Method for rectifying images of an elongated, preferably translucent, object generated by means of an optical coherence tomography method having the following steps: a capturing step, in which at least one region of the object is captured in at least one first orientation (γ1) in a first image and in at least one second, different, orientation (γ2) in a second image, preferably by an optical coherence tomography method; and a determination step, wherein corresponding reconstruction images (R1, R2) of the region are generated on the basis of the captured images, wherein at least one refractive index (n1, n2, n3) is determined, preferably iteratively, for each of a plurality of layers of the object on the basis of spatial, reconstruction deviations (Δexy) between the first and second reconstruction images, a rectification step, wherein a rectified overall reconstruction image is calculated based on the determined refractive indices (n1, n2, n3).