Bidirectional Laser Scanning for Doppler Shift Correction
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Solution Overview
Problem
Existing technologies fail to accurately correct Doppler shift during laser-based measurements of social infrastructure structures due to changes in scan direction and difficulty in measuring the same point multiple times, especially when the measurement target is stationary.
Innovation Solution
A measurement apparatus and method that acquires scan data in two different directions, and applies a spatial correction to remove the influence of Doppler shift by, and combines the data using averaging processing to cancel out the Doppler shift, allowing for accurate Doppler, and spatial correction, enabling high-accuracy three-dimensional shape measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser scanning is performed in a single direction to measure social infrastructure structures, then measurement speed is improved, but measurement accuracy deteriorates due to uncorrected Doppler shift
Solution Approach 1:
The patent implements periodic bidirectional scanning, alternating between forward and backward scanning directions. By periodically reversing the scanning direction, the system creates alternating Doppler shift signs that can be mathematically canceled through averaging, thereby maintaining high measurement speed while correcting accuracy degradation from Doppler effects
2Measurement precision
If the measurement target is scanned multiple times at different positions to correct Doppler shift, then measurement accuracy is improved, but device complexity and operation difficulty increase
Solution Approach 1:
The system uses its own scanning motion to generate the correction data. By scanning in alternating directions and using the known relationship between scan direction and Doppler shift sign, the system self-corrects without requiring external reference objects or complex additional measurement equipment. The laser scanner itself provides both the measurement function and the correction function
3Measurement precision
If pre-measurement is performed at multiple speeds to calculate correction values, then Doppler shift correction accuracy is improved, but measurement time increases
Solution Approach 1:
The patent performs Doppler correction calculations continuously during the scanning process itself, rather than requiring separate pre-measurement phases. By calculating correction values in real-time using the alternating bidirectional scan data, the system eliminates idle pre-measurement time and maintains continuous productive operation throughout the measurement process
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 method effectively corrects Doppler shift, enabling high-accuracy three-dimensional shape measurement and damage detection in infrastructure structures, improving measurement precision and efficiency.
Implementation Method 1
measurement accuracy (distance measurement accuracy) is reduced due to a Doppler shift in a case where a scanner and a measurement object are moving relative to each other
Data Source
AI summary
The present disclosure enables to correct a Doppler shift with high accuracy. In the measurement apparatus according to one aspect of the present invention, the processor acquire first scan data including information indicating a first distance, which is a distance from a laser scanner to a measure portion of an object, obtained by scanning the measure portion in a first direction with the laser scanner; acquire second scan data including information indicating a second distance, which is a distance from the laser scanner to the measure portion of the object, obtained by scanning the measure portion in a second direction different from the first direction with the laser scanner; and calculate corrected data in which an influence of a Doppler shift in the first scan data and the second scan data is removed by applying an averaging processing to the first scan data and the second scan data.