System Design And Research On Laser Imaging For Underwater Target

The ocean is an important domain for scientific and engineering research intwenty-first century. It is urgent to develop advanced methods to discover and exploitthe sea. In recent years, the laser imaging system for underwater target became a noveloceanic detection technique due to the development of high energy laser andoptoelectronic devices. Laser imaging system has the advantages of high resolution andhigh efficiency. In this article, laser imaging system for underwater target using pulsedlaser and streak tube is designed and discussed.Firstly, the structure and principle of the streak tube which is the key instrument ofthe laser imaging system for underwater target are presented. And the target rangedetection model for streak tube imaging system is built. The range detection capabilityof streak tube is discussed. Based on the field of view of streak tube imaging system,the lidar equation in large field of view is built. The relationship between detectionrange and attenuation coefficient is obtained.Secondly, a proto of streak tube laser imaging system is built. The hardware andsoftware of this imaging system including laser, synchronization module, optical system,programming and image processing algorithm are discussed.Thirdly, the property of laser propagation in water is analyzed. The comparativemeasurement of attenuation coefficient of laser light in water is investigated. Weprocess the values of laser light energy or power measured in multiple positions on theroute of laser propagation by data fitting to obtain the attenuation coefficient of laserlight in water precisely. We measure the attenuation coefficients of green pulse laser,continuous green and blue laser in the laboratory and then discuss the comparisons ofthem.Fourthly, an imaging experiment is carried out in the laboratory. We obtain theintensity image, range image and3D range image for targets situated15m far from theimaging system. The result of the experiment demonstrates the3D imaging capability ofstreak tube laser imaging system.