A fast automatic focusing method for infrared imaging system based on gradient calculation

The traditional automatic focusing method of infrared imaging system is often based on image clarity evaluation function, which controls servo motor to move from the starting position to the longest distance and finds the position with the highest image clarity evaluation function value in this path, and then controls the servo motor to move to that location. This paper puts forward a kind of infrared imaging fast automatic focusing method based on gradient calculation, which does not need to run the whole path, it firstly control the servo motor move to the position pre-calibrated, the image clarity evaluation near the position is monotonic and crest, on the basis of the feature with coarse and fine adjustment strategy for servo motor movement near the location, with less movement times, it can quickly find the position with the largest image clarity evaluation value based on gradient, so that it can quickly complete automatic focus. The experimental results show that this method can complete the auto-focusing of infrared imaging system within 3s, and the system has good stability and real-time performance.