A Multi-laser Center Location Algorithm With Auto-focusing

Fiber lasers are widely used in industrial, communication and medical fields because of their good beam quality, small size and low cost. Especially in the field of national defense, more and more attention has been paid to the application of fiber lasers. Due to the non-linear effect and thermal effect of fiber lasers, the power of a single laser is limited, and laser synthesis is an effective way to solve this problem,including coherent synthesis and non-coherent synthesis. The laser positioning problem in laser beam synthesis technology was researched in this dissertation, the main researches are as follows.1. CCD camera was used for the front part of laser tracking in laser beam positioning system, and CCD auto-focus process is a key step in system automation.Three key problems were discussed, including auto - focusing, namely image clarity evaluation function, focus window selection and focus search algorithm. Aiming at the problem of sparse image content of binoculars, an image segmentation focusing window search method is proposed. The image clarity is evaluated by using the sub grid with the largest gradient in the image combining with Tenengrad function. The experiment shows that this method improves the sharpness of evaluation function. With the problem of the autofocus process cost too much time caused by the long focal length of the telescope, this dissertation combined with the focusing characteristics of the telescope, a method of presetting the zoom position was proposed, shortening the focal length range of the search process and shortening the focusing time .2. The influence of atmospheric transmission on the laser positioning in the space was analyzed. Various kinds of noise in the atmosphere were added to laser, including natural noise and artificial noise, which limits the sensitivity of the receiving equipment.An improved soft and hard threshold wavelet de-noising method is proposed to make the wavelet coefficients have good continuity and can suppress the additional oscillation after reconstructing the wavelet, while keeping the edge information of the laser image.3. The threshold segmentation method is used to reduce the computational complexity in the image processing and to eliminate the interference of the background to the positioning process. By comparing the OTSU method and the KSW maximum entropy segmentation method in different scenes, the KSW maximum entropy method was proved to be adaptive and accurate while distinguish the spot image. In order to verify the ability of the KSW maximum entropy segmentation method to improve the localization accuracy of the laser spot, Simulation was designed.4. A method of transforming multi-spot image segmentation into single spot location by using regional growth marker method was proposed to solve the problem of multi-spot positioning. At the end of this dissertation, several laser spot localization algorithms were compared. The experimental results show that the improved Hough transform method has a good accuracy in the irregular spot image, which is better than the traditional Hough transform method, and the average error is decreased by about 36%relative to the gray Gravity method.