Research On The Detecting System For The Forward Light Scattered By Ship Wakes

Ship bubbles wakes is a streak of foamy and turbulent region behind a moving ship, which is a special production of ship movement. Any kind of physical characteristic of ship wakes is high usable for torpedo research. The main work of the thesis is to design and build up a system for detecting and analyzing the forward light scattered by ship wakes. The laser based photoelectrical detecting technology is used for the ship wakes detection. Through detecting the change of optical parameter of the scattering light, we can know whether the bubbles exists on the laser passing way, which can approve whether torpedo enters or get out of the ship wakes. As an experimental system, the system has many functions, such as measuring at different depth, with different incident light wavelength and different light path length and it also can detect the polarization characteristics of the scattering light. The system has low electric noise and balanced gain of the amplifying circuit. Experimental results demonstrate that the system is able to meet the requirements for actual application in the sea.The entire opto-electric detection system is hermetically sealed in a 7 meters high stainless steel frame, which is airtight and pressure tested by filling in 2atm air and immersing in water for 120hr. Experiment results also show that the SNR of the electrical system is lower than 60dB and the signal transmission (over 200m) is real time, accurate and interference resistant. The power stability of the 650nm laser is better than 95%, the power stability of the 532nm laser is higher than 91%. Simulated ship wakes detecting experiment is carried out with the system, which shows that the forward scatter light from the wakes bubbles could be clearly detected and recognized from the signal both in the time domain and frequency domain.