| As a key technology of underwater to air imaging systems,namely virtual periscopes,underwater to air imaging is widely used in submarine covert to air observation,sea and air early warning,and monitoring and broadcasting complex marine environment and hydrological information.However,there are many difficulties faced by this technology,such as randomly fluctuating sea waves that cause changes in the refraction and reflection paths of light at the water space interface,causing serious deformation and distortion of underwater images.At the same time,seawater has absorption and scattering effects on light,which can cause image color distortion and blurred details.Starting from the actual application requirements of virtual periscope,this paper carefully analyzes the current technical problems of water-air imaging technology,with the aim of improving the clarity and visibility of restored images,improving the restoration quality of distorted images,and reducing the time required to restore distorted images.The specific work is summarized as follows:(1)Firstly,the related transmission properties of light under water and at different water-air medium plane are studied and analyzed,and how it leads to image degradation is expounded.Secondly,through the experimental simulation,the underwater imaging through the Snell window and the boundary properties of the Snell window are explored.The influence curve of Snell window on the brightness of air target and the visual elevation range of underwater camera observation are given.Combined with the image degradation model under wavefront disturbance,the causes of image distortion are analyzed.(2)For randomly fluctuating waves,introducing adaptive and adjustable blue green structured light,an underwater to air imaging pattern integrating proactive and passive is constructed.And based on this model,a wave restoration method based on Helmholtz Hodge Decomposition(HHD)is proposed.Firstly,the structured light is projected onto the water surface,and the structured light image is distorted due to the random fluctuation of the water surface.Then the feature information of the twisted structured light is extracted and matched with the standard reference structured light to obtain the two-dimensional twisted vector field that causes the deformation of the water surface.Then,the Helmholtz-Hodge decomposition of the vector field is performed to estimate the wave surface and realize the real-time three-dimensional reconstruction of the ocean wave.Finally,through a large number of experimental simulations,the usefulness of the algorithm is tested.(3)Basis the research ideas in(2),a distorted image correction algorithm based on Helmholtz Hodge decomposition is come forward,which is further advanced on the basis of wavefront inversion.Firstly,the wave surface is sampled under calm water using structured light;Next,under the fluctuating water surface,the wavefront distorted structured light images captured by the underwater camera are filtered and eliminated using a customized image preprocessing method based on HSI space;Then,a feature point finding algorithm based on slope analysis is used to extract and match the characteristic message of the structured light picture carrying wave surface information to obtain the two-dimensional distorted vector field of the corresponding sampling point in the structured light image,and Helmholtz Hodge decomposition is performed on it.Combining finite difference and interpolation techniques,a dimensional transformation pattern of structured light is acquired,and combining the displacement ratio relationship between the reflected imaging structured light and the refractive imaging aerial target object,distortion correction of underwater aerial target objects is achieved;Finally,GPU parallel computing is used to accelerate its processing.(4)Basis the underwater air imaging pattern in(2),a real-time underwater to air distorted image restoration system platform is established.Combined with the distorted image restoration software designed and implemented based on the Helmholtz Hodge decomposition image restoration algorithm,real-time restoration and correction of the air distorted target image under water wave disturbance is achieved.Through multiple experimental tests,using image quality evaluation indicators and algorithm time consuming detection,the image correction results of this algorithm and traditional algorithms are compared and analyzed,thereby verifying the feasibility and efficiency of this algorithm,and also demonstrating the practical engineering value of the underwater space distortion image restoration experimental method and restoration algorithm proposed in this paper. |
