Laser Detection Of Underwater Acoustic Signals And Attenuate Low-frequency Waves

Underwater detection technology has important civil and military value in the field of ocean. At present, laser sonar technology is widely applied in underwater detection. However, it has not been insufficient to meet growing demand for underwater detection due to its poor mobility. A new detection technology which was combined with the sound detection technology and laser detection technology has been widespread attention in recent years.This paper discusses the method of detecting underwater target with the laser technology so far. Surface acoustic wave theory which was excitated by underwater sound source was analyzed. Surface acoustic wave of the one-dimensional theory model was established. The plane wave reflection and refraction were studies in water-air interface. From what has been discussed above,laser detection of underwater target is very feasible.A simple measurement system is developed to study the optical effect of the low-frequency liquid surface wave which excited by underwater acoustic source. The clear and high stable diffraction pattern is observed experimentally when the laser beam illuminates on the liquid surface which modulated by the underwater acoustic signal, the diffraction fringes is asymmetric distribution, and experiments and theory is very consistent. The relationship between surface wave amplitude and the distance which Surface wave propagation was studied. The analytical expression between diffraction patterns divergence angle and the liquid surface wave amplitude was theoretically derived. Surface wave amplitude were derived at different position. It was found that the surface wave amplitude is exponent attenuation with the change of the horizontal distance. The attenuation coefficients is dependent on the frequency of liquid surface acoustic wave, and the greater frequency, the smaller attenuation coefficient.