| NLC is uniaxial in optics and dielectric and anisotropic in electricity. And this make it possible to control optical performance with electric field. LC apparatus almost meet all the needs of space optical communication such as weight,size,power consume,life,cost,driving voltage,intergration of optics and electricity,programe, optically take–over aperture,beam scanning, deflexional range and so on.Switches, deflexional facilities and scanning equipments which made with LC have been used in the system of labor in space communication.The only bug of LC Apparatus is that their answer speed only get microsecond rate or submicrosecond rate.But it is practical for them to be used in special beam capture,scan,deflexion controling which don't concerned with code rate and code type.In this paper we demonstrated a new field-controllable liquid-crystal phase grating which to used in orientation detecting and automatic tracking and aiming in space communication. The basis is that when incident polarized light gets through a liquid-crystal box,it's first diffraction angle and optical intensity are controlled by periodic electric field .Difference iterative method was used to estimate numerically director configurations in the NLC-BL037 cell in this paper. The refractive indices and phase retard of NLC in electric field was presented on the basis of the calculation of liquid crystal director distributions. Then we analysed the diffraction phenomenon when the linearly polarized light was controlled by diffraction grating which was based on rectangular grating and sinusoidal phase grating models and we got it's math model。Finally we designed the NLC phase grating and we did the experiment to validate the theoretic calculation.There are two innovated points in this paper.The first is that we abandoned mechanical apparatus in deflexion,and this is good for signal's disposal.The second is that we adopted NLC facility and this will largely lighten APT systerm's size ,weight and power consumption. |
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