We report remote detection of oil using a flash Raman lidar system. The utilization of an expanding laser beam and an intensified CCD camera enabled the wide field-of-view observation, capturing the whole scene simultaneously. The second harmonic of a standard Q-switched Nd:YAG laser (532 nm) provided the illumination of the water and oil samples separately prepared under atmospheric conditions. We demonstrated the possibility of remote flash Raman lidar measurements using the interference filters at the water (649 nm) and oil (623 nm) Raman wavelengths.
The progress toward developing a technique for the underwater remote detection of gases using Raman lidar is reported. In this work, we describe the development of the marine Raman lidar system for monitoring the CH4 gas of Taketomi submarine hot spring. The transmitter of lidar system was the third harmonic of a standard Q-switched Nd:YAG laser (355 nm). The receiver of this system consisted by a telescope with a diameter of 200 mm, a spectrometer, a CCD camera for measuring Raman spectrum, and a PMT for monitoring Raman lidar signals. In order to evaluate the performance of our system, we demonstrated the Raman spectroscopic measurements from a barge down to the water depth of about 30 m.
High-speed laser remote sensing of defects inside a concrete specimen was demonstrated. In the proposed measurement setup, high-power laser pulses irradiated a concrete surface to generate vibration that can be detected by an optical interferometer, which was constructed using photorefractive crystal. The laser-based remote sensing system achieved inspection speeds of 25 Hz. The predominant frequency of a mock-up defect that was embedded in a concrete specimen was measured. The inspection result was identical to that obtained using a conventional hammering method.
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