| 研究実績の概要 |
The laser-based system for remote inspection of unstable structures like bouncing highway bridge has been developed, set up and tested in laboratory. The system prototype has been assembled and tested both in laboratory and field conditions - under real highway bridge.
CO2 laser generating pulses of 4 Joules energy and 100 ns duration is used as a source of laser impact initiating vibration in the inspected object. CW Nd:NYO laser with 0.5W output power is used as a source of probing beams.
The system uses two-beam probing to decrease degree of signal instability. In laboratory, specially designed samples representing defects in highway bridge span have been used. The system has demonstrated capability of artificial defect recognition. The system is equipped with specially designed algorithm of automatic scanning the inspected area and real-time processing of data obtained. Two-dimensional map of inspected area is produced in real time. In laboratory experiments, comparison between two-beam probing and conventional homodyne one-beam probing techniques has demonstrated significant benefit of using two-beam probing idea.
In the end of March 2016, the system mobile prototype was delivered under the bridge in Juso area, Osaka. The bridge has both highway and railway lines. Defects in concrete/metal interface have been located preliminary by hammering. The system has demonstrated capability of recognition of these defect. However, it was found that the system needs more careful protection against sunlight, wind and acoustic noise. We plan to improve the system.
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