Clear Underwater Imaging Based On Depolarization Of Scattering

Underwater polarization imaging has shown its powerful potential for many applications because it has simpler setup,less cost and better image quality.However,most of current polarization imaging methods emphasized to utilize the linear polarized component and neglect the circular polarized component during the whole clear imaging process.These methods failed when the degree of polarization between target and backscattering was similar.To overcome these problems,this thesis proposed an underwater Mueller matrix descattering imaging method based on depolarization in scattering environment.The proposed method used Mueller matrix measurement to acquire intensity information and polarization information.Then based on the characteristic of depolarization index(Dep)variation in turbid water condition,an optimal transmittance map was calculated.Finally,a clear underwater image was recovered by using the underwater imaging model of Mueller matrix.The innovative work in this thesis includes:i).we studied the variation of Dep caused by the scattering depolarization in the turbid water,and verified the feasibility to use Dep to reconstruct the clear underwater image in turbid water condition.We found that when the scattering particle was uniformly distributed,and its size was similar with the illumination wavelength,a negative exponential distribution was found between the Dep and the distance in Mie scattering region.We also found that there were differences about the Dep values between different objects,as well as between objects and the background.ii).we studied the relationship between Dep and backscattering intensity in turbid water condition.An approximate linear distribution was found there.This was why the Dep map could be used to estimate the backscattering and the transmittance map.iii).we combined Mueller matrix with the Jaffe-Mc Glamery imaging model,and established a clear underwater imaging method using Mueller matrix imaging in turbid water condition.The algorithm of this method was also presented.And the experiment shows the validity of the proposed method.As far as we know,it's the first time that the Mueller matrix was introduced into the clear underwater imaging.The proposed method solved the imaging problem for the targets with polarization-variation surface existed in turbid water condition.And it may inspire a thorough change in the clear underwater imaging achievement,and maybe helpful to develop the next generation underwater equipment which is more powerful and robust.