Unstructured scenarios play a critical role in specialty industries, where ensuring the health of their internal surfaces is essential for the safe operation of the device. However, the large depth-of-field variations within these surfaces often lead to insufficient or mismatched depth-of-field in conventional camera imaging, resulting in out-of-focus blur and poor defect detection. Therefore, this paper proposes a fast construction method of focused tracking curve based on an extreme value search algorithm, and realizes fast highdefinition imaging. Firstly, the basic construction method of the focused tracking curve was established. Secondly, an extreme value search algorithm is proposed to simplify the curve construction process. Finally, the construction of single / multi-focus tracking curves based on A/ B calibration plates was designed, and its influence on imaging clarity was analyzed. The results show that,the proposed algorithm effectively reduces the number of image acquisition times and increases the focusing speed by 34. 8% while focusing accurately. Based on the multi-focus tracking curve, the average value of the objective evaluation index of the image is increased by 10. 35% . Clear resolution of 0. 5 mm cracks is achieved under 100~ 1 000 mm depth of field span. Therefore, this method can provide a solution for high-definition full depth imaging in unstructured scenes with conventional cameras.