Research On High Precision Spot Extraction And Location Technology Based On Liquid Crystal Optical Closed-loop System

With the development of the information age,the use of laser as the carrier,the space laser communication technology with high transmission rate,large amount of information and large coverage has been greatly developed.The establishment and maintenance of space laser communication link is mainly determined by the performance of targeting,acquisition,tracking(PAT)system,while the traditional laser communication PAT system is transforming from mechanical servo to non-mechanical servo represented by liquid crystal optical closed-loop system.The high-precision positioning of the beacon spot is a prerequisite for the efficient operation of the liquid crystal optical closed-loop system,but under the special conditions of the liquid crystal grating,the beam will undergo Bragg diffraction,resulting in multiple diffracted spots.It has always been a difficult problem to quickly and accurately extract and locate the center position of the target spot in the diffracted spot.Therefore,The method of extracting and locating liquid crystal Bragg diffraction spot with high precision is studied in detail.In this paper,the relevant characteristics of Bragg diffracted spot in liquid crystal closed-loop system are expounded,and the influencing factors of spot imaging are analyzed.The median filtering method was selected to filter out the high-frequency noise in the diffracted spot image.The spot extraction method in the form of row and column scanning was adopted to accurately extract the main valve spot according to the energy characteristics of the spot.A spot positioning method based on Gaussian cross-section fitting is proposed to achieve high-precision positioning of target spots.At the same time,in the hardware implementation link,the relevant algorithms are improved,and methods such as parallel full comparison sorting and one-time scan of the connected domain are used to map.Through the simulation of the proposed method,it is concluded that under the condition of light saturation,the average absolute error of the positioning method proposed in this paper is 0.09 pixels in the X direction,the standard deviation is 0.12 pixels,and the average absolute error in the Y direction is 0.12 pixels,the standard deviation is 0.11 pixels.Under the influence of medium and weak turbulence,the average absolute error of the localization method in the X direction is 0.43 pixels,the standard deviation is 0.20 pixels,and the average absolute error in the Y direction is 0.30 pixels.The standard deviation is 0.23 pixels,and this paper proposes that the positioning method is better than the traditional positioning method in both the average absolute error and standard deviation;the experimental optical path of spot positioning accuracy analysis is designed,and the positioning effect calculated by several traditional algorithms is compared with the real spatial position of the spot,the mean value of the algorithm positioning results in this paper is closer to the real value,the deviation between the mean and the real value is always within 0.8 pixels,and the RMS value is always within 0.82 pixels,which means it has better stability;a spot tracking verification experimental platform is built to verify the effect of the proposed algorithm in actual tracking in the scenario of beacon light moving in different forms It is found that the algorithm in this paper can complete stable tracking within 3 oscillation cycles.