Fiber Optic Interferometer Adjustable Coupler Gap Control
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Solution Overview
Problem
Existing fiber optic interferometer systems for detecting ultrasonic waves in materials face low sensitivity due to diffusely reflecting or scattering surfaces, leading to aberrated and mismatched wavefronts, resulting in weak and imprecise signal detection.
Innovation Solution
A sensing apparatus with a fiber optic interferometer that includes an adjustable coupler to set a precise gap between the probe segment end and the target, allowing the distance to be a desired fraction or multiple of the wavelength of light, minimizing distortions and using a pulsed laser and optical couplers for accurate data generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser probe beam is directed onto a diffusely reflecting or scattering material surface, then the surface vibration can be detected, but the reflected beam becomes highly aberrated and mismatched with the reference beam, resulting in low sensitivity and weak signal
Solution Approach 1:
A lens is introduced as an intermediary optical element between the diffusely reflecting target surface and the photodetector. The lens collects scattered light from the target and refocuses it to form a coherent interference pattern, thereby reducing wavefront aberration and improving measurement precision without changing the fundamental diffuse reflection nature of the target surface.
Solution Approach 2:
The system transitions from direct beam detection to detecting the interference pattern in the focal plane of a lens. By moving the detection plane to the focal region where the scattered waves converge, the system exploits the spatial dimension transformation to convert incoherent scattered light into a detectable interference pattern, thereby improving sensitivity despite diffuse reflection.
2Measurement precision
If the gap between the probe segment end and the target is fixed, then the system structure is simple, but path length fluctuations occur leading to reduced accuracy in ultrasonic wave detection
Solution Approach 1:
The gap between the probe segment end and the target surface is made dynamically adjustable rather than fixed. A positioning mechanism allows the gap distance to be precisely controlled and adapted to different measurement requirements, thereby eliminating path length fluctuations and improving detection accuracy while adding only moderate system complexity.
Solution Approach 2:
The gap distance parameter is changed from a fixed value to an adjustable parameter. By allowing the gap distance to be optimized for different target surfaces and measurement conditions, the system achieves improved measurement precision without requiring complex adaptive control systems, simply by making the geometric parameter variable.
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 enhances the accuracy and precision of ultrasonic wave detection by minimizing path length fluctuations and aberrations, enabling the determination of material properties such as dimensions, composition, and thickness with improved sensitivity and reliability.
Implementation Method 1
fiber optic interferometer configured to sense the induced waves in the target
Implementation Method 2
When the surface vibrates it imparts a phase shift onto the reflected beam
Implementation Method 3
allowing the distance to be a desired fraction or multiple of the wavelength of light, minimizing distortions
Data Source
AI summary
A sensing apparatus comprises an excitation source configured to induce waves in a target, and a fiber optic interferometer configured to sense the induced waves in the target. The fiber optic interferometer comprises a probe segment having a probe segment end, and an adjustable coupler configured to permit setting a gap between the probe segment end and the target. A controller is coupled to the adjustable coupler and configured to set the gap between the probe segment end and the target.