The research of underwater imaging based on the wavefront coding system

Abstract

Current research on the underwater imaging often needs particular techniques. Since the specificity of the underwater imaging system, it must overcome the impact of the turbulent and turbid of the water. In this paper we present a new application of the wavefront coding (WFC) system in the underwater imaging. Wavefront coding system is a two-step imaging system, by using a cubic phase mask with optimized parameters; we get the defocus-insensitive intermediate image in the imaging plane. Then the final sharp image can be obtained by deconvoluted the intermediate image with the point spread function (PSF). Initially the wavefront coding system is introduced to extent the depth of the field of the optical system and the allowance of the system can be great improved by using the optimized cubic phase mask. Because of the defocus-insensitive property, this system can eliminate the aberration brought by the turbulent of the water. The deconvolution can improve the imaging quality by deblurring intermediate image and reduce the impact brought by the turbid of the water. In order to get excellent result, we propose to use the global generalized minimal residual method as the deconvolution algorithm. Antireflective boundary conditions (BCs) are considered to eliminate ringing effect, and Kronecker product approximation is introduced to reduce the computation consumption. This method can give excellent deconvolution result. There is little ringing effect on the image border and little vibration on the edge. Theory analysis and the experiment show that this is an effective system in the underwater imaging. It is an economical system.