Dynamic Compensation Strategy for Beam Pointing Based on Cascaded Liquid Crystal Polarization Gratings Using Liquid Crystal Optical Phased Array

As a core non-mechanical beam-steering device, cascaded liquid crystal polarization gratings (CLCPGs) suffer from insufficient pointing accuracy due to inherent fabrication and assembly errors, which must be compensated by liquid crystal optical phased array (LCOPA). However, in practical working conditions, LCOPA is vulnerable to coupled internal and external disturbances as well as inherent time delays, which prevent accurate compensation and limit the performance of the integrated system. To overcome these challenges, this paper proposes a novel composite control strategy. An improved observer and an improved Smith predictor are designed to estimate and compensate for the total disturbances and time delays, and parameter tuning is accomplished using the phase margin method. The effectiveness of the proposed strategy is validated on a LCOPA coarse–fine two-stage compensation system experimental platform. The results demonstrate that the strategy can effectively suppress disturbances and compensate for LCOPA errors, reducing the overall pointing error by more than 30% and increasing the dynamic response speed by 25%, while exhibiting excellent robustness and stability. This study provides theoretical and technical support for the engineering application of high-precision CLCPG scanning systems.