The sky background infrared radiation characteristic is of great significance to target detection and extraction is of great significance. Using 3~5 micron medium wave, 8~12 microns long wave infrared measuring equipment has carried on the long-term measure to the sky background infrared radiation intensity. In this paper, the difference of the sky background infrared radiation brightness was contrast researched between the cloudless fine weather and cloudy sky of foggy weather, the influence was also analyzed of the different observation angles, the sun position and atmospheric temperature on the sky background radiation. The research results show that the infrared radiation intensity in the cloudy sky background under foggy weather is greater than in the cloudless weather clear sky, background infrared radiation intensity of long wave under the condition of same sky background radiation luminance brightness is higher than that of bilateral radiation. As the observation Angle increases, the sky background radiation intensity decreased significantly, and the decreased amplitude of sky background radiation brightness is higher under small angle than under large angle. At the same time, the factors such as solar radiation, air temperature also have a great influence on the sky background radiation. The researched result will be useful to the infrared target detection and indentification.
A flat structure element is usually used in the traditional morphological detection. In this processing method, the infrared target is regarded as a single point without considering the imaging characteristics of infrared dim and small target. There is a gray transition zone between target and background. It is unreasonable that the transition region processed as background in the traditional morphological method. So, the infrared dim target detection results are not ideal by using the traditional morphological processing method. Aimed at this problem, the imaging characteristic of infrared dim and small target is analyzed. The Spatial distribution of infrared target gray scale is calculated. The result shows it is a tip package structure. The top peak is the target. Based on theoretical research on the morphological detection, the girdle structure elements are designed. This structure is composed of two circles. The target neighborhood zones are protected in this structure. They do not participate in the morphological calculation. The sixteen external zones are only participated in the calculation. The morphology of infrared target detection method is established based on this neighborhood zoned structure. The designed girdle structure is used in the opening operation and the traditional flat structure is used in the closing operation. The traditional Top-Hat algorithm is improved according to the girdle structure morphology method. And used the real infrared target image, the improved algorithm is simulated. The processed result shows that the girdle structure morphology method is effective in the background noise restraining. In order to evaluate the image processed result quantitatively, the signal noise ratio and signal noise ratio gain factor are used. Accordingly to the calculated result, the improved algorithm compared with the traditional morphological methods, inhibition of complex background with better.