Real-time image enhancement processing methods of low contrast visible light over-the-horizon imaging

Although the CCD imaging system has been used widely in the area of border surveillance, the weather has a great impact on its effective distance. The investigated and analyzed results on the principle and technical means of the over-the-horizon CCD imaging show that the visibility distance of the system increases by 1.5 times at most under the condition of using the optical near-infrared filter only, so the digital image processing means must be adopted to enhance the contrast of scene image. The limitation of traditional enhancement method of overall gray transformation was analyzed, the partially overlapped sub-block local histogram equalization algorithm was proposed to obtain the goal observation of the scene more than two times of the visual distance.