Vibration-Based Laser Interferometry for Non-Contact Defect Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing defect detection methods using speckle interferometry or speckle shearing interferometry face challenges in detecting defects in hard-to-access locations and incur high costs due to the need for an excitation device and communication equipment, especially when the inspection object is in a difficult-to-reach place.
Innovation Solution
A defect detection method that emits continuous or quasi-continuous laser light to a vibrating inspection object, generating integrated intensity by shifting the phase of reflected laser light or reference laser light, and obtaining a distribution of interference to detect defects without an excitation device, utilizing environmental or artificial vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an excitation device is attached to the inspection object to generate vibration, then defect detection accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The inspection object utilizes its own environmental vibrations (from traffic, wind, or operational conditions) to generate the necessary vibration for defect detection, eliminating the need for external excitation devices. The system captures and processes these naturally occurring vibrations to detect defects, making the inspection object serve its own inspection needs.
Solution Approach 2:
The patent replaces the mechanical excitation device with an optical-based vibration sensing system using laser interferometry. Instead of mechanically exciting the object and measuring the response, the system uses laser light to detect the object's natural vibrations, substituting a mechanical system with an optical measurement system.
2Measurement precision
If an excitation device and communication equipment are used for defect detection, then measurement precision is improved, but cost increases
Solution Approach 1:
The system eliminates expensive excitation and communication equipment by using the inspection object's own environmental vibrations. The laser interferometry system processes these natural vibrations directly, removing the need for additional costly components while maintaining defect detection capability.
Solution Approach 2:
The patent employs a cost-effective laser interferometry measurement system that captures vibration information passively without requiring expensive, complex excitation devices and communication equipment. The system uses readily available laser technology and standard interferometry techniques to achieve accurate defect detection at lower cost.
3Loss of time
If only one image of interference pattern is acquired, then measurement time is reduced, but defect detection accuracy becomes location-dependent
Solution Approach 1:
The system captures multiple interference pattern images at different time points during the vibration cycle, corresponding to different phases of the vibration. By analyzing the vibration state across multiple phases, the system reconstructs the complete vibration pattern, enabling accurate defect detection regardless of the defect's location on the inspection object.
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 defect detection without the need for an excitation device or communication equipment, reducing costs and allowing detection in hard-to-access locations by leveraging existing vibrations, such as those from traffic or manual tools, while maintaining high accuracy.
Implementation Method 1
an interference pattern due to the light of the irradiation light reflected at each point on the surface of the inspection object in the measurement region and the reference light is acquired
Implementation Method 2
emitting laser light continuously or quasi-continuously from a laser light source for a time longer than a period of vibration generated in an inspection object to a measurement region on a surface of the inspection object in a state in which the vibration is being generated in the inspection object
Data Source
AI summary
A defect detection device 10 is provided with: a laser light source 11 for irradiating laser light to a measurement region R of a surface of an inspection object S; a laser light source control unit 15 for controlling the laser light source so as to cause laser light to be outputted continuously or quasi-continuously for a time longer than a period of vibration generated in the inspection object; an interferometer (speckle shearing interferometer 14) for generating interference light in which reflected light of the laser light reflected in the measurement region and reference laser light emitted from the laser light source 11 interfere; a detector (image sensor 145) for detecting the intensity of the interference light for each point in the measurement region R; a phase shifter 143 for shifting the phase of the reflected laser light or the reference laser light; an integrated intensity pattern determination unit 16 for obtaining an integrated intensity obtained by integrating the intensity for each point over an integration time longer the period of the vibration in three or more phases, the phase being shifted by the phase shifter 143 into three or more different phases; an interference degree distribution generation unit 17 for obtaining the distribution of the degree of interference based on the integrated intensity obtained in each of the three or more phases for each point; and a defect detection unit 18 for detecting a defect in the measurement region R based on the distribution of the degree of interference in the measurement region R.