| In recent years,oil spills have occurred frequently in the surrounding waters of the country,seriously damaging the domestic marine ecological environment.Accurate identification of the type of oil spill is an important basis for quick handling and accurate traceability of oil spill incidents.However,the marine environment is complex and changeable,and traditional photoelectric detection methods often have problems such as high false alarm rate,poor real-time performance,and low discrimination ability when monitoring oil spills.It is difficult to meet the urgent needs for accurate detection and identification of oil spills.This paper proposes a combination of visible light and infrared,and a combination of intensity and polarization to distinguish marine oil spills.First,based on the theory of polarization imaging,the analytical expressions for the degree of polarization of visible light/infrared on calm and fluctuating water surfaces were derived,and a model of the degree of polarization of the oil spilled in the reflection space was constructed.The changing law of parameters such as angle,azimuth,refractive index,etc.;Then,the error caused by the polarization imaging method of the sub-focal plane in the oil spill detection process is analyzed,and the polarization characteristics of the optical system itself,the processing error of the micro-polarizer array,the response non-uniformity,and the polarization detection effect of the system calibration process are analyzed.influences;Based on the above analysis,the polarization-maintaining method of the polarization optical system is clarified,which reduces the polarization measurement error caused by the imaging system,thereby improving the accuracy of oil spill identification.In addition,a visible/infrared dual-band common-aperture polarization imaging optical system based on a split-focus plane polarization detector is designed.The front end of the system uses common-aperture reception,and the back end uses wavelength splitting to receive both the oil-spilled visible light polarization image and long-wave infrared polarization image.The dual-band design ensures that the field of view matches,which facilitates subsequent image fusion processing,and further improves the probability of oil spill identification.The design results show that the modulation transfer function of the visible light system is better than 0.5 at the Nyquist frequency 71lp/mm,and the modulation transfer function of the infrared system is better than 0.3 at the Nyquist frequency 30lp/mm.The tolerance analysis results show that the tolerance is relatively loose.The imaging quality of the system within the range meets the actual use requirements.Finally,a polarization-maintaining experiment of polarization imaging based on a splitfocus plane polarization detector was carried out.After correction,the contrast of the visible light intensity image was increased by more than 5%,the contrast of the visible light polarization image was increased by more than 7%,and the contrast of the infrared intensity image and the polarization image were increased by more than 3%;A multi-spectral polarization detection test for marine oil spills was carried out outdoors,and the experimental results show that: using visible light or infrared technology can only distinguish some oil type,but combined with the polarization information can not only distinguish between heavy oil and light oil,but also different types of light oil.Analyzing the polarization contrast of oil spill,the results show that: the polarization contrast between various oil types is generally higher than 5%,and the oil type discrimination effect is more obvious,which proves that the visible light,infrared and polarization multi-dimensional detection methods are effective in marine oil spill detection.The advantages and feasibility can provide an effective supplement to traditional oil spill detection methods and are of great significance to improving the ability of marine pollution control. |
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