Research On Enhanced Detection Of Ship Target Based On Polarimetric Characteristics Of Sea Surface

Infrared detection technology has extensive application prospects in the field of national military security,and it is the main means to achieve efficient surveillance of ships on the sea.In the process of persistent monitoring of the marine targets,due to the continuous changes of solar radiation flux and atmospheric heat convection,the temperature of the ship surface on the sea is in the process of dynamic changes.The ship target is not detectable when the radiance difference between the ship and the sea is less than the resolution of the infrared detection system,which is called the thermal crossover period.Thermal crossover is the main challenge of infrared detection system for target monitoring,which seriously reduces the operating efficiency of infrared detection system.In response to this problem,this dissertation uses polarimetric infrared detection system to improve the detection efficiency by enhancing the contrast of ship targets,based on the strong polarimetric characteristics of the sea surface.This article first briefly introduces the demonstration and verification system,and illustrates the ability of the system to extract the polarization features of the scene through the noise equivalent degree of polarization in the polarization mode.Then,according to the infrared radiation characteristics of the ship scene on the sea surface,the characterization model of the degree of polarization and the target contrast of the sea surface is established,and the influencing factors of the degree of polarization and contrast are analyzed through numerical simulation,and the demonstration experiment is performed to verify the actual sea surface.Degree of polarization range.Then,the mathematical model of the detection efficiency of the system in the intensity and polarization detection mode is established,and the main factors affecting the improvement of detection efficiency are analyzed,and the threshold contrast of the system for stable detection of ships on the sea surface is deduced through actual measurement analysis.Then the method of numerical analysis and experimental verification is used to prove the direction selectivity of polarization to improve the contrast of the target.Based on this,an orthogonal polarization detection method is proposed to realize the removal of the thermal cross environment,and its boundary conditions are analyzed.Finally,the established model and conclusions are applied to the space-based detection platform,and the efficiency of space-based polarization detection is simulated and analyzed.The innovations of this article mainly include the following three aspects:(1)The current characterization methods for the detection efficiency are mainly aimed at traditional intensity detection systems.In the polarization detection mode,detection scenes with strong polarization characteristics cause different polarization contrasts due to the anisotropy of radiance,which have different effects on the system signal-to-noise ratio.This paper analyzes the relationship between the sea surface polarization angle,the radiation passing direction of the system polarizer and the suppression of background radiation,and introduces the polarization suppression ratio to quantify the relationship between polarization contrast,entrance pupil contrast and sea surface polarization,and analyze the polarization threshold contrast of the system.(2)The research on the improvement of the target polarization detection efficiency in the thermal cross environment is currently all experimental demonstrations,and no quantitative analysis has been carried out on the principle.In response to this problem,this paper establishes a characterization method using threshold contrast as the boundary of the thermal cross environment,combines system performance with the radiation characteristics of the scene,and analyzes the improvement percentage of the system polarization detection mode to the target response contrast in the thermal cross environment and the system signal-to-noise ratio.Demonstration experiments are carried out to verify the improvement of target contrast under different system polarization angles.(3)Aiming at the problem of the thermal crossover period in the current traditional detection system when detecting sea ships and other targets,this paper proposes to use the orthogonal polarization detection method to reduce the contrast range of the thermal cross environment,the quantitative relationship between target polarization contrast and atmospheric extinction coefficient,detection distance,and noise equivalent contrast is established,and the boundary conditions for realizing a thermal cross environment are obtained.