Acoustic Probe Light Guide Securing Material Refractive Index
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Solution Overview
Problem
In photoacoustic imaging, light leakage occurs due to a small refractive index difference between light guide plates and commonly used potting agents, leading to inefficient light reflection and reduced image quality.
Innovation Solution
A probe design that secures light guide plates with a securing material having a lower refractive index than the light guide plates, ensuring the critical angle for total reflection is smaller than the maximum incidence angle, preventing light leakage and enhancing light guidance to the acoustic wave detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a commonly used potting agent (epoxy resin with refractive index 1.42-1.45) is used to secure light guide plates, then the probe body is properly secured and components are fixed, but light leakage occurs due to small refractive index difference between the light guide plates and the potting agent
Solution Approach 1:
The patent changes the refractive index parameter of the securing material from conventional epoxy resin (1.42-1.45) to fluororesin (1.35-1.40), creating a larger refractive index difference with the light guide plate (1.47-1.50). This parameter change enables total internal reflection at the interface, preventing light leakage while maintaining securing functionality.
Solution Approach 2:
The patent applies a specific securing material (fluororesin) only at the interface between the light guide plate and the surrounding environment, where light reflection is critical. This localized application of a material with specific optical properties (lower refractive index) solves the light leakage problem at the critical interface without affecting other parts of the probe structure.
2Loss of energy
If a securing material with lower refractive index than light guide plates is used, then light leakage is prevented through total internal reflection, but the selection of securing materials becomes more restricted
Solution Approach 1:
The patent identifies fluororesin as a specific material class with refractive index (1.35-1.40) lower than light guide plates (1.47-1.50), transforming the material selection from conventional epoxy resin to fluororesin. This parameter-based material selection ensures total internal reflection while providing adequate securing strength.
3Loss of energy
If reflective coatings are applied to light guide plates to prevent light leakage, then light reflection efficiency is improved, but production costs increase and device complexity increases
Solution Approach 1:
The patent removes the reflective coating layer from the light guide plate structure by using a securing material with inherently lower refractive index. This extraction of the unnecessary coating layer simplifies the device structure, reduces production steps, and eliminates the associated costs while achieving the same light reflection function through material property selection.
Solution Approach 2:
The patent converts the previously harmful light leakage (caused by matching refractive indices) into a beneficial total internal reflection effect by deliberately selecting a securing material with a lower refractive index. This transforms the interface from a light-leaking boundary to a light-reflecting boundary, eliminating the need for additional reflective coatings.
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 effectively prevents light leakage, ensuring efficient light application to the subject and minimizing image intensity loss, while reducing production costs by eliminating the need for reflective coatings.
Implementation Method 1
the critical angle for total reflection is smaller than the maximum incidence angle, preventing light leakage and enhancing light guidance to the acoustic wave detector
Implementation Method 2
An ultrasound probe including a light application section is taught in Japanese Unexamined Patent Publication No. 2008-49063
Data Source
AI summary
An acoustic wave detector that detects an acoustic wave from a subject, an optical fiber that guides light emitted from a light source to a probe body, and a light guide member that guides light from a light entrance end, which is optically coupled to the optical fiber, to a light exit end, which is located in the vicinity of the acoustic wave detector, are provided. The light guide member is secured in the probe body with a securing material provided at least partially around the light guide member. The conditional expression below is satisfied:sin−1(n2/n1)×(180°/π)<90°−θi where n1 is a refractive index of the light guide member, n2 is a refractive index of the securing material, and θi is a spread angle of incoming light from the optical fiber.