针对传统爬山搜索算法受调焦评价函数局部极值的干扰而不能准确聚焦的问题，提出一种基于调制传递函数辅助正焦判断的自动调焦搜索算法.该算法对爬山法进行改进，在选择图像清晰度评价函数基础上，同时考虑图像的调制传递函数值，综合判断搜索方向; 采用改进的刃边法，在自动完成刃边区域选择的基础上，可精确计算图像的调制传递函数值，并给出了改进算法的原理和实现. 为了衡量改进算法的性能，验证调焦系统成像效果，分别考虑搜索算法对不同调焦初始位置以及环境变化影响，在经纬仪自动调焦系统平台上展开算法的调焦实验分析.实验结果表明改进的自动调焦搜索算法能有效地排除局部极值干扰，使系统准确、可靠的调焦.

Traditional climbing search algorithm cannot usually focusing accurately due to the interference of evaluation function local extremum effected by measure environment. A searching algorithm of auto-focusing based on MTF auxiliary focal judgment was introduced to improve the climbing method. Definition evaluation function and MTF values of images were considered at the same time. And based on those results, search direction was judged. Slanted-edge method was improved to calculate the image MTF values accurately based on the auto-selection of slanted-edge area. At last, the principle and implementation of the improved algorithm was given. In the theodolite auto-fousing system, the system imaging effect was validated, and different initial position and circumstance were considered using the proposed searching algorithm. The experiment results of theodolite auto-focus system show that the improved climbing search algorithm can effectively eliminate the local extremum disturbance, and make the system searching focusing accurately and reliably.