Defect Detection Device Using Elastic Wave Interferometry
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Solution Overview
Problem
Existing defect detection methods using speckle interferometry or speckle shearing interferometry struggle to detect defects obscured by shielding members, as they can only observe interference light reflected from the surface and fail to detect defects outside the observable range.
Innovation Solution
A defect detection device that excites an elastic wave with a specific vibration mode and direction, using an excitation source positioned on the inspection target, and employs speckle interferometry or shearing interferometry to measure displacement in multiple phases, allowing detection of defects through reflected or scattered waves, even when partially obscured by shielding members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If speckle interferometry or speckle shearing interferometry is used to measure surface displacement, then defect detection capability is improved, but defects obscured by shielding members cannot be detected
Solution Approach 1:
The patent transitions from two-dimensional surface displacement measurement to three-dimensional subsurface defect detection by utilizing the propagation and reflection of elastic waves through the object's interior. The elastic wave source generates waves that penetrate the object, and sensors detect reflected waves from defects at various depths, enabling detection beyond the surface plane.
Solution Approach 2:
The patent introduces elastic waves as an intermediary medium to detect defects. Instead of directly observing surface displacement, the system uses elastic waves that propagate through the object and reflect off subsurface defects, carrying information about hidden defects to the sensors. This intermediary enables indirect detection of defects obscured by shielding members.
2Measurement precision
If a dot-shaped detection laser is used in laser interferometry, then measurement precision is improved, but scanning time increases significantly
Solution Approach 1:
The patent replaces the mechanical scanning system with an acoustic wave-based detection system. Instead of moving a dot-shaped laser across the surface, the system uses elastic waves that naturally propagate and cover the inspection area, with sensors detecting reflected waves from defects throughout the region simultaneously, eliminating the need for time-consuming point-by-point scanning.
3Measurement precision
If elastic wave amplitude varies across the inspection area, then detection sensitivity at high amplitude regions is improved, but defects in low amplitude regions become undetectable
Solution Approach 1:
The patent employs dynamic signal processing techniques to handle varying wave amplitudes. The system captures reflected wave signals at different time points and uses signal processing methods to normalize and reconstruct the defect information, ensuring consistent detection sensitivity across regions with different initial wave amplitudes.
Solution Approach 2:
The patent changes the detection parameter from direct displacement measurement to reflected wave signal analysis. By detecting the characteristics of reflected waves (time of flight, amplitude, frequency content) rather than direct surface displacement, the system achieves uniform detection sensitivity regardless of the incident wave amplitude distribution across the inspection area.
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
Enables the detection of defects both within and outside the observable range, improving sensitivity and accuracy by generating and analyzing elastic waves with controlled amplitude and phase, effectively overcoming the limitations of previous methods.
Implementation Method 1
excite an elastic wave in an inspection target object
Implementation Method 2
measure a displacement of each point in a front-back direction within an illumination area in at least three different phases of the elastic wave, by speckle interferometry or speckle shearing interferometry
Implementation Method 3
measure a displacement of each point in a front-back direction within an illumination area in at least three different phases of the elastic wave, by speckle interferometry or speckle shearing interferometry
Implementation Method 4
the interference pattern by the light which is the illumination light reflected at each point on the surface of the inspection target object within the inspection area and the reference light is obtained
Implementation Method 5
detect either one or both of a reflected wave and a scattered wave of the elastic wave
Implementation Method 6
detect either one or both of a reflected wave and a scattered wave of the elastic wave
Data Source
AI summary
[PROBLEM] To provide a defect detection device capable of detecting not only a defect within a visible range but also a defect outside the visible range among the objects to be inspected. [SOLUTION] A defect detection device 10 includes: an excitation source 11 capable of being placed at any position on a surface of an inspection target object S, the excitation source 11 being configured to excite an elastic wave within the inspection target object S, the elastic wave being predominant in one vibration mode and propagating in a predetermined direction; an illumination unit (pulsed laser light source 13, illumination light lens 14) configured to perform stroboscopic illumination on an illumination area of the surface of the inspection target object by using a laser light source; a displacement measurement unit (speckle shearing interferometer 15) configured to collectively measure a displacement of each point in a front-back direction within the illumination area in at least three different phases of the elastic wave, by speckle interferometry or speckle shearing interferometry; and a reflected wave/scattered wave detector 16 configured to detect either one or both of a reflected wave and a scattered wave of the elastic wave, based on the displacement measured by the displacement measurement unit.