Modeling And Simulation Of Underwater Acoustic Daylight Imaging System Using Reflector

In the field of underwater acoustic detection, ambient noise is considered an interference which degrades the performance of sonar. A great body of work on active and passive sonar systems is how to restrain the noise, while ambient noise is regarded as useful information when using underwater noise as the sole illumination for target detection and imaging.The main parts of this thesis are modeling and simulation of acoustic daylight imaging system. In the thesis, the basic principle of acoustic daylight imaging is researched and the imaging system is constructed. The acoustic lens consists of a concave mirror and a planar transducer array located at the image plane of the concave mirror, and the wave scattering from a target will be focused and received by the acoustic lens to achieve the visible image of the target. Based on the Helmholtz integral with the Kirchhoff approximation, the signal receiving model of acoustic lens and the acoustic scattering model of the target have been made, and stationary phase method is used to evaluate the scattering wave. The model of underwater noise field is composed of the stable single-frequency point sources independent from each other, and different noise field can be obtained by changing the number and the position of the sources. According to the internal relationship between the three sub-models, the model of acoustic daylight imaging system is connected.Lots of simulations on imaging of rigid sphere and square rigid board have done respectively. The performance of the acoustic daylight imaging system as a function of incident direction of the noise, frequency of the noise and target size is discussed, and some valuable simulation data for reference are obtained.