Membrane-Free Optical Microphone for Material Joint Testing
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Solution Overview
Problem
Existing methods for testing material joints and interfaces face challenges such as the need for position-sensitive detectors, large scanning areas, and poor signal-to-noise ratios, particularly in narrowly defined geometries and confined spaces.
Innovation Solution
A method using membrane-free optical microphones to detect ultrasound waves generated by laser pulses, which excite acoustic waves in material joints, allowing for mode conversion analysis and standing wave evaluation without direct surface interaction, enabling efficient testing of material joints and interfaces in restricted spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position-sensitive photodetector is used to detect ultrasound waves, then the detection capability is improved, but the device complexity and scanning area requirements increase
Solution Approach 1:
The patent replaces the mechanical position-sensitive photodetector system with a membrane-free optical microphone that uses optical interference to detect acoustic pressure directly. This substitution eliminates the need for complex mechanical positioning and scanning systems while maintaining high detection precision for ultrasound waves generated by laser excitation.
Solution Approach 2:
The patent introduces an optical field as an intermediary between the laser excitation source and the detection system. The membrane-free optical microphone uses laser light to probe acoustic pressure variations through refractive index changes, creating an optical mediation layer that simplifies the direct mechanical detection approach while enhancing measurement capabilities.
2Device complexity
If laser and membrane-free optical microphone are rigidly connected and positioned on one side of the arrangement, then the setup simplicity is improved, but the scanning area significantly increases
Solution Approach 1:
The patent transitions from a lateral scanning approach to a vertical detection geometry. By positioning the membrane-free optical microphone above the material joint and utilizing the vertical propagation of acoustic waves, the system achieves effective testing without requiring extensive lateral scanning area, thus resolving the contradiction between setup simplicity and scanning area requirements.
3Measurement precision
If optical microphone is positioned next to welded joint, then the detection sensitivity is improved, but the adaptability to narrowly defined geometries decreases
Solution Approach 1:
The patent inverts the conventional positioning approach by placing the membrane-free optical microphone above the material joint rather than beside it. This inverted vertical positioning enables the system to detect acoustic waves propagating upward from the joint, significantly improving adaptability to narrowly defined geometries and confined spaces while preserving detection sensitivity through the air-coupled optical measurement principle.
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 approach improves the detection of material quality features by utilizing membrane-free optical microphones to analyze acoustic pressure variations and mode conversions, providing accurate assessments of material joints and interfaces with enhanced signal-to-noise ratios and reduced scanning requirements.
Implementation Method 1
exciting of acoustic waves in at least one component in the provided arrangement to be tested, with laser pulses from a laser light source
Implementation Method 2
The optical microphone directly measures the change of the refractive index in air, caused by the pressure difference within an ultrasound wave. The change of the refractive index is detected with an interferometer, a so-called Fabry-Perot-etalon
Implementation Method 3
The change of the refractive index is detected with an interferometer, a so-called Fabry-Perot-etalon, where a laser is reflected within a cavity of two partially reflecting mirrors
Data Source
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AI summary
The invention discloses a method and apparatus for testing material joints or material compounds having at least the following steps: (a) providing an arrangement to be tested consisting of at least two components, connected via a material joint, (b) excitation of acoustic waves in at least one component, in the provided arrangement to be tested, with laser pulses from a laser light source, (c) detecting ultrasound waves in a gaseous layer adjacent to the provided arrangement to be tested with a membrane-free optical microphone, (d) evaluating the ultrasound waves detected by determining an acoustic pressure variation of the ultrasound waves. Followed by e) evaluating the respective material joint based on the occurring mode conversion of a symmetrical mode with a first out-of-plane deflection into an asymmetrical mode with a second out-of-plane deflection, and/or based on acoustic standing waves at resonant frequencies in the material joint.