Research On Underwater Laser Imaging And Image Processing Technique

Underwater laser imaging utilizing the unique characteristics in aspects of spectral, time and spatial of blue-green laser in seawater to image underwater targets, This make up for the lack of underwater sonar system in aspects of imaging resolution and close detection, and thus achieve a large area detection with high speed and high precision. it has a good application in the fields of military and civilian. With increasingly fierce competition and deepening development for marine resources, underwater laser imaging technology has become a competing research hotspot in the world. This article will carry out the research on three aspects in underwater laser transmission, range-gated imaging and underwater image processing.Water is a special environment in which there are a large number of medium and suspended particulates. When lights spread in the water there is a serious scattering and absorption effects, what is the main cause of high noise and low contrast in the underwater imaging. According to the characteristics of light wave transmission in the water and the optical scattering theory, we conductor a systematic analysis and calculations for the scattering properties of the particles in aqueous media, then derived the law of effluent medium decaying exponential, the correlation between seawater optical properties and optical parameters. Simulate the time-domain broadening characteristics of pulse width when laser transmission in water with the method of small angle approximation, obtain the relationship between the time- domain broadening and transmission distance, water quality parameters. By studying characteristics of light wave transmission in water, analysis the factors that impact underwater imaging distance and image quality, thus seeking ways to improve.Underwater laser range-gated imaging technology is an effective method to inhibit to back scattering of seawater particulates. Through modeling the laser transmission in seawater, we analyze and calculate the reflected signal power of target and the back scattering power of water. Then obtain the relationship between target reflected signal power, the backward scattering power and the factors as imaging distance and attenuation coefficient in water. Based on this, we deduce the SNR formula for range-gated imaging system, and then analyze the key parameters that affect the imaging performance of the system, which provides a theory basis for the design of underwater laser imaging system.At last,we analyze characteristics of images collected in underwater laser imaging system. On the basis of research on evaluation for underwater image, we use traditional algorithm to process underwater image,we study the applicability of traditional algorithm in underwater image processing. On this basis, we propose a method that based on judgment the type of image noise to process the underwater image.