FMCW Laser Interferometry for 3D Shape and Vibration Measurement
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Solution Overview
Problem
Existing methods for measuring the three-dimensional shape and vibration of social infrastructure structures like roads, bridges, and buildings are cumbersome and costly due to the combination of three-dimensional shape measurement and non-contact acoustic inspection systems, leading to potential errors and omissions in damage detection.
Innovation Solution
A measurement system utilizing a frequency-modulated continuous wave (FMCW) laser light source for both three-dimensional shape and vibration measurement, combining a laser scanner, interferometer, shape measurer, and vibration measurer to simplify the configuration and enhance detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three-dimensional shape measurement and non-contact acoustic inspection are performed using separate systems, then measurement coverage is comprehensive, but device complexity and cost increase
Solution Approach 1:
The patent combines three-dimensional shape measurement and non-contact acoustic inspection functions into a single integrated measurement system. The laser scanner performs both distance measurement for shape reconstruction and vibration measurement for acoustic inspection by analyzing frequency components of the reflected light, eliminating the need for separate inspection systems while maintaining comprehensive damage detection capability
Solution Approach 2:
The laser scanner is designed to perform multiple functions: it measures three-dimensional shape by calculating distance from phase information, and simultaneously performs non-contact acoustic inspection by detecting vibration frequencies from frequency components of the reflected light. This multi-functional approach allows one device to replace multiple specialized instruments
2Device complexity
If a single laser light source is shared for both shape and vibration measurement, then system size is reduced, but measurement precision may be compromised
Solution Approach 1:
The measurement process is segmented into distinct signal processing pathways: phase information extraction for distance/shape measurement and frequency component analysis for vibration measurement. By separating the analysis methods while using a common laser source, the system maintains high precision for both measurement types without mutual interference
Solution Approach 2:
The system uses frequency modulation of the laser light at specific rates to enable simultaneous extraction of both phase and frequency information. By applying excessive modulation and then selectively analyzing different components of the modulated signal, the system ensures sufficient precision for both shape and vibration measurement from a single light source
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 accurate measurement of both three-dimensional shape and vibration with a simple setup, allowing for precise detection of damage such as delamination by sharing a laser light source for both functions, reducing system size and cost.
Implementation Method 1
a frequency-modulated continuous wave (FMCW) laser light source
Implementation Method 2
an interferometer that splits the frequency-modulated continuous wave laser light into reference light and measurement light, and causes the reference light and reflected light of the measurement light reflected by the object to interfere with each other
Implementation Method 3
a laser scanner that scans an object with the frequency-modulated continuous wave laser light
Data Source
AI summary
The present invention enables to measure a three-dimensional shape and vibration of an object with a simple configuration. A measurement system includes: a laser light source that outputs frequency-modulated continuous wave laser light; a laser scanner that scans an object with the frequency-modulated continuous wave laser light; an interferometer that splits the frequency-modulated continuous wave laser light into reference light and measurement light, and inputs and causes the reference light and reflected light of the measurement light reflected by the object to interfere with each other; a shape measurer that measures a three-dimensional shape of the object based on a center frequency of a beat signal obtained by the interference; an FM demodulator that performs FM demodulation on the beat signal obtained by the interference to detect FM sidebands; and a vibration measurer that measures vibration of the object based on the FM sidebands obtained by the detection.