3D Shape Reconstruction Using Fiber Optic Strain and Torsion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for 3D shape reconstruction of optical fibers embedded in elongated devices, such as endoscopes and guidewires, fail to accurately calculate local curvature and torsion from strain measurements, which are crucial for precise tracking and evaluation of the device's shape.
Innovation Solution
An optical shape sensing system that includes an optical fiber with embedded cores, an optical interrogation console for generating reflection spectrum data, and a 3D shape reconstructor that calculates local strain, curvature, and torsion angles to reconstruct the 3D shape of the fiber, using techniques like Fourier transforms and Jacobian matrix updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to calculate local curvature and torsion from strain measurements, then the 3D shape reconstruction can be performed, but the accuracy of curvature and torsion calculation is insufficient
Solution Approach 1:
The patent transforms the calculation approach by changing from direct strain-to-curvature conversion to a differential geometry-based method. It introduces new parameters including the Jacobian matrix for coordinate transformation, Frenet-Serret frame vectors (tangent, normal, binormal), and curvature-torsion relationships derived from the derivative of the position vector. This parameter transformation enables accurate calculation of local curvature κ = ||d²r/ds²|| and torsion τ from the strain measurements through proper mathematical transformation.
Solution Approach 2:
The patent replaces the conventional mechanical/empirical strain-to-curvature conversion method with a mathematical/differential geometry-based system. It uses the Frenet-Serret formulas and Jacobian matrix transformations to substitute the direct mechanical interpretation of strain with a rigorous mathematical framework that accounts for the fiber's three-dimensional configuration and orientation changes.
2Ease of manufacture
If the art's method of combining strain data is used, then 3D shape reconstruction is achieved, but the method fails to address how line elements are calculated or how the conversion matrix is established
Solution Approach 1:
The patent performs preliminary calculations by establishing the Jacobian matrix and Frenet-Serret frame before computing curvature and torsion. It pre-defines the tangent vector T = dr/ds, normal vector N, and binormal vector B, and establishes the coordinate transformation matrix before the actual shape reconstruction. This preliminary setup ensures that all necessary mathematical tools are in place for accurate subsequent calculations.
Solution Approach 2:
The patent introduces the Jacobian matrix as an intermediary that bridges the strain measurement data and the final 3D shape reconstruction. The Jacobian matrix serves as a transformation mediator that converts local strain measurements in the fiber's coordinate system to the global reference frame, enabling accurate calculation of curvature and torsion through proper coordinate transformation.
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 system provides accurate 3D shape reconstruction of optical fibers within elongated devices, achieving sufficient accuracy for medical applications like EP ablation and stent placement with minimal deviation, typically within the order of 10 microns over a meter.
Implementation Method 1
The first step involves a multi-core fiber being interrogated with optical frequency domain reflectometry, which results in the measurement of both an amplitude and a phase of a reflection for each core as a function of wavelength. The reflection may be invoked by embedded periodical structures (e.g., fiber Bragg gratings) or by non-periodic, random variations in the refractive index (e.g., Rayleigh scattering).
Implementation Method 2
The second step involves a calculation of strain in each core at multiple positions along the fiber from the reflection spectra.
Data Source
AI summary
An optical shape sensing system employing an elongated device, an optical fiber embedded within the elongated device with the optical fiber, an optical interrogation console and a 3D shape reconstructor. In operation, the optical interrogation console generates reflection spectrum data indicative of a measurement of both an amplitude and a phase of a reflection for each core of the optical fiber as a function of wavelength. The 3D shape reconstructor executes a generation of local strain data for a plurality of positions along the optical fiber responsive to the reflection spectrum data, a generation of local curvature and torsion angle data as a function of each local strain along the fiber, and a reconstruction of the 3D shape of the optical fiber as a function of each local curvature and torsion angle along the optical fiber.