SUBTRACTION OF BACKPROPAGATION INTERFERENCE BASED ON POLARIZATION IN UNDERWATER VISION SYSTEMS FOR OPERATION IN TURBID WATER

Abstract

The study of the sea depths in order to ensure safety, the effective use of underwater resources
is an urgent task. The first part of the article briefly considers the physical phenomena and
limitations that arise during the propagation of electromagnetic waves in the visible range in the
underwater environment. It is shown that underwater vision systems (as a class of specialized
technical vision systems - TVS) based on conventional CCD matrices face a number of fundamental
limitations in terms of improving the efficiency of functioning in natural water of low transparency.
In particular, the use of artificial light sources as part of underwater vision systems in turbid
water leads to the occurrence of backpropagation interference (BPR), which leads to spurious
illumination of the optical device matrix. As a promising direction in the development of underwater
vision systems, it is proposed to use methods for subtracting POR based on information about
the polarization of light. In the review part of the article, the latest achievements in this field are
considered. The main part of the article presents the methodology for studying the proposed method
for subtracting the POR based on a comparison of the results obtained by processing images
with known methods for estimating the Stokes vector parameters DoLP and AoLP, which allow
obtaining information about the degree of polarization and the prevailing polarization angles of
the scene, respectively. The experimentally obtained results of processing an underwater scene in
water of varying degrees of turbidity using the DoLP, AoLP algorithms and the proposed methods
for subtracting the POR are presented. Distinctive features are the use of four rather than two
polarization directions in calculations, as well as the original mathematical apparatus for processing
signals from the machine vision camera matrix.