The Monte Carlo Simulation Of Laser Underwater Target Detection

Comparing to the underwater sonar detection, the technology of underwater laser target detection has a lot of advantage in the marine detection field such as high precision and high efficiency. It is a new kind of advanced detection technology including many technologies such as laser, communication, signal processing and object identification, electronic technique and so on. It has very important practical value at ocean exploitation such as search and rescue, underwater reconnaissance, target recognition.The research background and situation of underwater laser target detection technology are introduced. And several technologies of green-blue laser underwater target detection developed in recent years are discussed such as range gated imaging system, synchronous scanning system, polarized laser imaging system, streak tube imaging lidar system. Meanwhile the optics properties such as absorption, scattering, inherent optical properties and apparent optical properties are described in detail. The process of how the blue-green laser transmit in the seawater was simulated with Monte Carlo algorithm. The laser propagation space and time characteristics' change along with the water quality parameters and other system parameters were analyzed. Three power characteristics, which were forward scatter, backward scatter and echo signal, were discussed. The simulated results show:1.With the transmit distance increasing, the radius of forward scatter light spot is increased and the change becomes stable after reaching a certain distance. The light intensity has a downtrend which looks like analogous exponential when the transmit distance increases. In the same transmit distance with different water quality parameters, the light spot sizes have great difference and the light intensity is decreased significantly.2.The seawater attenuation coefficient has a very significant influence to backward scatter power. With the transmit distance increasing, the backward scatter power which received by the underwater laser target detection system is increased at first and attenuated exponentially after reaching the peak value.3.The scatter times are increased and the echo signal power is decreased with the distance increasing. The seawater's absorption and scattering are increased and the echo signal power is decreased when the attenuation parameter and some other water quality parameters are increased.