Research On Acquiring And Tracking Moving Object Based On Optical Phased Array

Laser radar plays an important role in the protection of space security, mainly used for spatial moving object searching, acquiring and tracking. As a multiple-laser-beams control in laser radar, optical phased array has such advantage as real time, no inertia and high precision. Compared to conventional laser rader, the laser rader used optical phased array can track moving object with more flexible way, high efficiency, high precision, therefore, method of acquiring and tracking moving object based on optical phased array is researched.One of the advantages of optical phased array is changing the shape and energy distribution of beam flexibly and agilely, which can form active lighting closed-loop tracking system with real-time image acquisition system. Optical phased array can generate variable laser net to search moving object, once found, Optical phased array changes the shape of the light adaptively, to make energy focus on the moving object. In this system, acquiring and tracking moving object software system should find and segment object from laser net image firstly, next predict the target trajectory and control the direction of laser net to make it cover the moving object all the time, in order to use active lighting to track moving object high efficiently, fast and stably. The main contents and achievements are described as following.(1) Theoretical method of acquiring moving object is studied in the condition of laser net lighting. In theory, method of acquiring moving object consists of moving object detection, image threshold segmentation and image filtering. On the basis of image gray characteristics, many different methods of moving object detection, image threshold segmentation and image filtering are studied separately, and methods of acquiring moving object are compared with simulation in order to determine fast and stable acquiring method. In the determined method, firstly moving object is detected by background differencing, secondly the noise of moving object image is attenuated by median filter, thirdly the image is segmented by OTSU method, at last the hole of object image is eliminated by morphological filter.(2) On the basis of acquired moving object, method of tracking moving object is studied, and consists of moving object image tracking and spatial transformation. Moving object image tracking does not only calculate the centroid position of object in current frame, but also predict the centroid position of object in next frame through gate centroid tracking method. And moving object spatial transformation transforms centroid position of imaged object to the real position of object for controlling the direction of laser net, in order to track object with the active lighting. (3) In order to validate the feasibility of the proposed method of acquiring and tracking moving object, tracking experiments have been performed. The experimental platform with optical phased array is designed to acquire and track moving object, and software is developed to achieve acquire and track moving object based on optical phased array. Experimental results demonstrate that the proposed method above can fast and stably track moving object in the condition of active lighting.