Optical Shape Sensor Interface for Precise Fiber Core Alignment
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Solution Overview
Problem
Existing optical shape sensing guidewires face challenges in accurately aligning the relative starting positions of fiber cores for 3D shape reconstruction due to variable refractive index steps at the connector interfaces, which are influenced by sterility barriers and contamination, leading to cross-talk and inaccurate signal measurements.
Innovation Solution
Implementing a partially reflective and substantially transmissive optical interface at the transition from the optical coupling member to the proximal optical fiber end, with a well-defined refractive index step, to serve as a stable starting point for shape reconstruction, ensuring accurate alignment of fiber core positions down to the micron level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If GRIN lenses are used in optical connectors for backloadable guidewires, then compactness and low surface reflection are achieved, but variable refractive index steps at connector interfaces cause inaccurate alignment of fiber core positions
Solution Approach 1:
A sterile barrier foil is introduced as an intermediary layer between the two GRIN lenses at the connector interface. This foil serves as a mediator that maintains sterility while its uniform compression creates a stable, predictable refractive index step that can be used as a reliable reference marker for aligning fiber core positions during shape reconstruction.
Solution Approach 2:
The refractive index profile is deliberately modified by introducing the sterile barrier foil with different refractive index properties than the surrounding media. This creates a distinct refractive index step at a known position, transforming the variable interface into a stable optical marker that enables precise measurement and alignment of time delays in optical response signals.
2Reliability
If sterile barrier foils are compressed between connector ends, then sterility is maintained, but variable compression alters the refractive index step and reflection intensity
Solution Approach 1:
The variable compression of the sterile barrier foil, which initially causes reflection intensity variations, is transformed into a beneficial feature. The compression creates a well-defined refractive index step at a predictable position, which serves as a stable optical marker for alignment. The harm of variable reflection is converted into the benefit of a reliable reference point for shape reconstruction.
Solution Approach 2:
The sterile barrier foil is pre-compressed between the connector ends during assembly, establishing a stable refractive index step before the guidewire is used for shape sensing. This preliminary compression ensures that the optical marker is already in place and stable, enabling accurate alignment measurements from the first use without requiring additional calibration steps.
3Measurement precision
If refractive index steps are used for aligning fiber cores, then starting position alignment is achieved, but cross-talk from variable reflections overwhelms weak optical response signals
Solution Approach 1:
The sterile barrier foil acts as an intermediary that creates a controlled refractive index step, mediating between the two GRIN lenses. This intermediary produces a stable, predictable reflection that serves as a reliable alignment marker without generating excessive cross-talk, as its position and optical properties are well-defined and consistent.
Solution Approach 2:
The refractive index step is localized to a specific position at the sterile barrier foil interface, creating a focused optical marker rather than distributed reflections. This local concentration of the refractive index change provides a clear, distinct signal for alignment while minimizing scattered reflections that could cause cross-talk and overwhelm the weak optical response signals from the fiber cores.
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
The solution enables precise measurement and alignment of time delays in optical response signals, improving the accuracy of 3D shape reconstruction by minimizing cross-talk and maintaining signal integrity despite environmental variations.
Implementation Method 1
the transition from the optical coupling member to the proximal optical fiber end has a well-defined refractive index step that serves as a stable starting point for shape reconstruction
Implementation Method 2
A respective peak of a reflection intensity distribution of input light reflected at the optical interface is identified in the optical response signals
Data Source
Figure 1~2
Figure 3~4
Figure 5(A)~6(C)
AI summary
The present invention relates to an optical shape sensor (OS), comprising an optical fiber (F2) having a length defining a longitudinal direction, the optical fiber (F2) having at least two fiber cores (C21, C22) extending along the length of the optical fiber (F2), an optical coupling member (OCM2) arranged at a proximal optical fiber end of the optical fiber (F2), the coupling member (OCM2) having a first distal end face (OF2) optically connected to the proximal optical fiber end, and a proximal second end face (IF2) spaced apart from the first distal end face (OF2) in the longitudinal direction of the optical fiber (F2), the optical coupling member (OCM2) being configured to couple light into each of the fiber cores (C21, C22, C23). An optical interface (OI) at a transition from the optical coupling member (OCM2) to the proximal optical fiber end is partially reflective and substantially transmissive, wherein the optical interface (OI) is arranged in such a distance distally from the proximal second end face (IF2) and is configured such that light is reflected at the optical interface (OI) with a reflection intensity distribution which substantially does not overlap with a reflection intensity distribution of light reflected at the second end face (IF2) of the optical coupling member (OCM2).