| Underwater imaging is a very important method for submarine exploration,marine resources exploitation,subsea biological monitoring and identification.However,due to selective absorption and scattering of light by water,different wavelengths of light are attenuated differently,making the color of underwater imaging seriously distorted.Moreover,the color distortion becomes more obvious in distance.Based on national 863 project "Research on underwater hyperspectral imaging technology for target detecting and identifying",this paper presents a set of underwater spectral imaging system based on filter wheel.It can provide underwater spectral images of known targets,which is valuable reference for the future studing of 863 project,attributing to object detection and identification.A set of underwater spectral image system is developed initially,which contains hardware and software of imaging module,control system,structure of pressure cabin and sealing system.Autofocus method is adopted to meet the need of imaging at short distance.A series of tests and calibrations of the underwater spectral imaging system are carried out,including the range of imaging bands,resolution of sensor,as well as absolute radiation and sensitive limit.And spectral images are obtained in the air and underwater respectively,with the target of color plate.Then the multi-scale Retinex with color restoration(MSRCR)is adopted to enhance color plate images obtained from different narrowband bands.The information entropies of the spectral imagings obtained in the air and water are calculated and compared.The experimental results show that underwater spectral imaging technology combined with image enhancement algorithm based on MSRCR can improve the ability of color reduction effect of underwater image obviously.The main achievement of this paper is the development and test of an underwater spectral imaging system based on filter wheel.The results show that it meets the requirements of the index.The spectral imaging range is 400～700nm,the spectral resolution is 10nm,and the radiation correction accuracy is better than 10%.The spectral image can be acquired under underwater 50m. |
