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Image matching is an important topic in the field of computer vision, in view of high robustness and accuracy, SIFT or the improved methods based on SIFT is generally used for image matching algorithms. The traditional SIFT method is implemented on grayscale images without regard to the color information of images, which may cause decreasing of the matching points and reduction of the matching accuracy. Prevailing color descriptors can effectively add color information into SIFT, however dramatically increase the complexity of algorithm. In this paper, a novel approach is proposed to take advantage of the color information for image matching based on SIFT. The proposed algorithm uses the gradient information of color channel as the compensation of luminance channel, which can effectively enhance the color information with SIFT. Experimental results show that the number of feature points and matching accuracy can be significantly promoted, while the complexity and performance of image matching algorithm are well trade-off.

The dark current noise existing in the CCD of the astronomical observation camera has a serious influence on its working performance, reducing the working temperature of CCD can suppress the influence of dark current effectively. By analyzing the relationship between the CCD chip and the dark current noise, the optimum working temperature of the red band CCD focal plane is identified as -75℃. According to the refrigeration temperature, a cooling control system for focal plane based on a thermoelectric cooler (TEC) was designed. It is required that the system can achieve high precision temperature control for the target. In the cooling control system, the 80C32 microcontroller was used as its systematic core processor. The advanced PID control algorithm is adopted to control the temperature of the top end of TEC. The bottom end of the TEC setting a constant value according to the target temperature used to assist the upper TEC to control the temperature. The experimental results show that the cooling system satisfies the requirements of the focal plane for the astronomical observation camera, it can reach the working temperature of -75℃ and the accuracy of ±2℃.