Abstract:In the autonomous navigation of deep space exploration based on optical imaging, image edge processing directly affects the extraction of visual vector, which has a great influence on the accuracy of autonomous navigation. Otsu scheme is one of the most widely used image thresholding techniques. The traditional Otsu algorithm focuses more on the uniformity of the pixels in the same area, and it is suitable for situations where the target area and the background area in the image have little difference. Therefore, in the initial stage of autonomous navigation, navigation accuracy is low. In the new algorithm, according to the characteristics of the Mars image captured in the cruise section, then on the basis of Otsu scheme, an improved algorithm is proposed to redesign the criterion function, the variance of area where the gray value is higher than the undetermined threshold is expressed as a function of it, and the gray value correspond to maximum of this function's first order differential is taken for the optimal threshold. This method has the advantages of small computation and accurate image segmentation. The simulation results show that compared with Otsu scheme, the image threshold obtained by the improved algorithm can realize higher visual vector extraction accuracy and autonomous navigation accuracy.