Image Guide Fiber High Numerical Aperture Thermal Expansion Control
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Solution Overview
Problem
Increasing the numerical aperture of image guide fibers to improve image quality while preventing manufacturing issues caused by significant differences in refractive indices between core and clad glasses, which can lead to manufacturing strain and breakage.
Innovation Solution
Developing an image guide fiber with cores and clads made of multi-component glass, where the numerical aperture is between 0.70 and 0.90, and the linear thermal expansion coefficient difference is within a specific range, ensuring a higher glass-transition temperature for the core glass and a lower one for the clad glass, along with a core occupancy area ratio of 25% or more and a pixel density of 0.1 pixel/µm² or higher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the numerical aperture NA is increased by making the image guide fiber of multi-component glass with significant difference in refractive index between core glass and clad glass, then the minimum thickness of the clad between adjacent cores that is sufficient to fully prevent crosstalk is reduced, but manufacturing problems occur due to significant difference in physical properties between core glass and clad glass
Solution Approach 1:
The patent changes the physical parameters of the glass materials by carefully controlling the linear thermal expansion coefficient difference (Δα) to be within -3×10-7/℃ to 15×10-7/℃ and the glass-transition temperature relationship (Tg1 > Tg2). These parameter changes allow achieving high numerical aperture (0.70-0.90) for reduced clad thickness while maintaining manufacturing feasibility through controlled thermal property matching.
2Measurement precision
If the core diameter is reduced for higher pixel density, then the pixel density increases, but the core occupancy area ratio decreases
Solution Approach 1:
The patent changes the optical parameters by increasing the numerical aperture to 0.70-0.90, which allows maintaining high pixel density (0.1 pixel/μm² or more) while improving light gathering capability. This compensates for the reduced core occupancy area ratio (25% or more) resulting from smaller core diameters, thereby maintaining image brightness despite higher pixel density.
3Measurement precision
If the thickness of the clad between adjacent cores is reduced to increase both pixel density and core occupancy area ratio, then image quality improves, but crosstalk of transmitted light occurs
Solution Approach 1:
The patent changes the optical parameters by achieving high numerical aperture (0.70-0.90) through controlled refractive index differences, which allows using thinner clads while preventing crosstalk. The high NA confines light more effectively, enabling reduced clad thickness without significant crosstalk, thus improving image resolution and brightness simultaneously.
Solution Approach 2:
The patent uses a simplified approach by controlling the thermal expansion coefficient difference within a relatively wide range (-3×10-7/℃ to 15×10-7/℃) rather than requiring precise matching, making the manufacturing process more feasible while still preventing crosstalk effectively.
4Power
If the linear thermal expansion coefficient difference between core glass and clad glass is increased to achieve higher numerical aperture, then the numerical aperture increases, but manufacturing strain and breakage occur
Solution Approach 1:
The patent optimizes the thermal property parameters by controlling the linear thermal expansion coefficient difference (Δα) within -3×10-7/℃ to 15×10-7/℃. This parameter control allows achieving high numerical aperture (0.70-0.90) while preventing excessive thermal stress during manufacturing and operation, thereby maintaining fiber strength and preventing breakage.
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 configuration enhances image quality by reducing clad thickness, preventing crosstalk, and ensuring manufacturing feasibility by managing thermal expansion and glass transition temperatures, thus avoiding fiber breakage and improving brightness and resolution.
Implementation Method 1
a linear thermal expansion coefficient difference Δα, which is a value obtained by subtracting a linear thermal expansion coefficient α2 at from 100°C to 300 °C of a clad glass of the clad, from a linear thermal expansion coefficient α1 at from 100°C to 300 °C of a core glass of the core
Implementation Method 2
a glass-transition temperature Tg1 of the core glass is higher than a glass-transition temperature Tg2 of the clad glass
Implementation Method 3
the image guide fiber has a numerical aperture NA in the range of 0.70 to 0.90
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Provided is an image guide fiber that improves image quality while preventing a manufacturing problem. The image guide fiber according to the present disclosure has a numerical aperture NA in the range of 0.70 to 0.90. A linear thermal expansion coefficient difference Δα, which is a value obtained by subtracting a linear thermal expansion coefficient α2 at from 100 to 300 °C of clad glass, from a linear thermal expansion coefficient α1 at from 100 to 300 °C of core glass, is in the range of - 3 × 10-7 / °C to 15 × 10-7 / °C. A glass-transition temperature Tg1 of the core glass is higher than a glass-transition temperature Tg2 of the clad glass. A core occupancy area ratio is 25 % or more. A pixel density is 0.1 pixel / µm2 or more.