Research Of Overdriving Of The Liquid Crystal Wavefront Corrector

Liquid crystal wavefront corrector is the core device of liquid crystal adaptiveoptical system. Slow response is the key problem which prevents the liquid crystaladaptive optical systems from engineering. The design and synthesis of high Δn andlow viscosity nematic liquid crystal materials can improve the response of liquidcrystal wavefront corrector. However, the potential of the improvement of theresponse become more and more limited. Therefore, based on the liquid crystaldynamics theory, this thesis researched the liquid crystal hydrodynamic process ofdirector rotation behavior. When the driving voltage changes from the higher voltageto the lower voltage, the distribution of the director of the liquid crystal is closer andcloser to the equilibrium state, and the rotational speed is slower and slower. Thisserious tailing phenomenon cause the average speed of response greatly reduced.Overdriving is applying a higher voltage difference than the normal driven to drivethe liquid crystal molecules to reach the target phase faster.Based on the elastic theory of liquid crystal, this thesis derived the equilibriumequation and the hydrodynamic equation of the liquid crystal devices under theelectric field without distortion. The effect of the cell gap and voltage on the phaseresponse process is researched. Through the optimization of cell gap, the responsedelay of liquid crystal wavefront corrector can be reduced. By increasing Δ, theresponse delay can be shortened under the overdriving condition. This thesis studied the driving scheme of the commercial liquid crystalwavefront corrector and the optimization of various parameters systematically. Bythe analysis of the time domain error and simulation, according to the relevantparameters of the system,1.155ms was choosed as the optimal response delay. Thefast overdriving matrix data processing and transition are realized using GPU. Thetime needed is about30us which makes this method can be directly applied tocommercial liquid crystal wavefront corrector. The single frame overdriving isapplied to the open-loop Liquid crystal adaptive optics system. The bandwidth testand the outfield experiment showed that the system performance is significantlyimproved. The–3dB bandwidth is improved from27Hz to35Hz. on the basis of thesingle frame overdriving, the single frame overshoot overdriving and multi-frameoverdriving is proposed, which can further reduce the residual wavefront correctionerror.Through mathematical derivation, the mathematical relationship between theinput and the output of the residual error was obtained. The precised calibrationscheme was proposed to improve the phase level to gray level map precision further.The improved method of overdriving matrix measurement is put forward. The effectof temperature on the overdriving was studied.