Study On The Range Forecast Of IR Images Detecting System Under Sea-sky Background

The infrared thermal imaging system has been more and more widely used on the battlefield as its unique advantage. However, the tactical performance of the system is influenced by various factors such as t he performance of the system itself, target characteristic, atmospheric environment and so on. So, the study on the effective distance of the IR images detecting system under different weather conditions is necessary. Because the export limits of foreign on s uch software and related technologies, and although domestic has made great progress after extensive research, but there are still insufficient in the model of the target and the background radiation and the atmospheric model. In view of this, this paper carried out the research work in the study on the range forecast of IR images detecting system. The main research in the following areas:1. The range equation based on the MRTD is the main basis to describe the performance of IR imaging system, however, it will produce large error in the calculation process of the traditional distance equation. This paper analyzes the causes of the calculation error and the change rule, and then offers a new expression which is more in line with the actual physical process accords to the definition of MRTD and the basic principle of the IR images system. Finally, this paper deduced a distance equation based on the image radiation calibration method after analysis the influence of atmospheric path radiation.2. The key of range forecast is to get the radiation of target and background in the entrance pupil of the system, usually, we calculate this radiation by the self-radiation of target and background combined with atmospheric attenuation. However, the atmospheric physics process is very complicated and there is no complete atmospheric model and meteorological data in domestic, so usually it's difficult to calculate and the accuracy is not high. This paper shows that we can calculate the radiation of background through the 14 bit images which were collected by IR thermal imager and the radiation calibration data. This method detect the sea-sky-line at first, and then confirm the size of background with the relevant information at the basis of sea-sky-line, finally calculated the radiation of background according to the average grey value of background region in 14 bit image and the radiation calibration data.3. To complete the range forecast, this paper also model the target radiation with the atmospheric transmittance and atmospheric path radiation calculated by MODTRAN, and then calculate the MRTD of the system which has been corrected, finally solve the equation by iteration method which has used bisection method to speed up the solution. This paper offered a computing software which is written in C# on the basis of these theories. After the radiation calibration experiment and sea-sky experiment have been completed, we input related data into the program to calculate the effective distance, the result shows that, the range calculated in this paper is more accordance with actual situation.