emtek 2113 High deflection efficiency is one of the urgent requirements for practical liquid crystal optical phased array (LC-OPA).In this paper, we demonstrate that high order grating lobes induced from fringe effect are the most important issue to reduce occupation of main lobe.A novel theoretical model is developed to analyze the feature of grating lobes when the device of LC-OPA is working on the scheme of variable period grating (VPG) fbd191blrc or variable blazing grating (VBG).Subsequently, our experiments present the relevant results showing a good agreement with the theoretical analysis.