Study On Beam Directing, Tracking And Aiming Technique Based On Liquid Crystal Phased Array

Acquiring tracking and pointing technique is widely used in fields of laser communication, laser radar, direction energy weapon and so on. The conventional beam tracking and directing technique depends on complicated mechanical transmission devices, resulting in complicated structures, substantial masses, high energy consuming. In recent years, as development of optical phase array(OPA) technique, it has been a new focus in beam control area. For it can realize beam control quickly, conveniently and non-mechanically, now OPA technique has been used in fields of beam shaping, optical tweezers, beam steering and so on. In the present paper, LCOPA(Liquid crystal optical phased array) based beam directing and tracking technique is studied systematically and some meaningful results are achieved as follows:1. This paper begins with reviewing conventional beam steering technique which is used in beam tracking and aiming area, then the research trend of LCOPA is previewed and the advantages of LCOPA is analyzed.2. Beam steering technique based on LCOPA is studied systematically. We established the physical model of LCOPA, and study the steering performance of LCOPA from theoretical analysis based on wave optical theory. Then fringing effect and fillfactor are studied in detail. Combined with stochastic parallel gradient descent(SPGD) algorithm, beam steering is realized. Beam steering method based on mode control is introduced in order to optimize the beam steering. We proposed a beam steering technique based on OPA to improve beam steering efficiency and precise, and beam steering with SPGD is demonstrated based on LCOPA for the first time3. A LCOPA based beam directing and tracking system is set up and analyzed. First, a LCOPA based system is designed. Combined with control theory, we establish the transfer function of the LCOPA system and analyze the basic target model. Target imaging, centroid location of primary phase error and atmospheric turbulence’s influence is analyzed based on the incoherent imaging theory. Both tilt and atmospheric turbulence will make an influence on the centroid location, we need to make compensation of it. We make a conclusion of tracking error of the LCOPA tracking system in the theory.4. Beam directing and tracking experiment based on LCOPA is studied. First, a new beam scanning and location method was raised based on imaging processing method. Beam directing and aiming system is realized, and the system has a maximum pointing error of 57μrad. Finally, beam tracking and aiming which is based on LCOPA and CCD running continuously is achieved. The system has a tracking field of view(FOV) of ±22mrad in one dimension, and can track the target which has an angle velocity of 2.78mrad/s. The system has a tracking FOV of ±12.88 mrad in two dimension, and can track the target which has an angle velocity of 0.69mrad/s. Beam aiming and tracking based on LCOPA is demonstrated for the first time.