The optical axes of electrically tunable liquid crystal (LC) lenses are usually tilted, and the corresponding asymmetric wavefront aberrations hinder the lenses from being diffraction-limited. Looking back at the literature studies since 1979, researchers used different approaches to compensate the tilting of the optical axis for achieving a perfect lens, or they utilized the intrinsically asymmetric wavefront aberration as a physical-planar free-form optics. However, the physics behind axis tilting has not been discussed yet, and the origin of the oblique optical axes of LC lenses in terms of anisotropic properties of molecules requires an investigation. In this paper, we study the origin of the asymmetrical tilting of optical axes of LC lenses. We found that the initial anisotropic molecular tilts (the so-called pretilt angle) result in the dielectric torque difference even under a rotationally symmetric electric field. Moreover, it is discovered that the rotational symmetry of the wavefront can be broken by generating uneven tilt angles of the LC molecules even though the electric potential is rotationally symmetric. Numerical results are presented and discussed to illustrate the mechanism.

中文翻译：

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在对称电场下，由初始各向异性分子倾斜引起的电可调聚焦透镜的倾斜光轴的原点。一世

电可调液晶（LC）透镜的光轴通常是倾斜的，并且相应的不对称波前像差阻碍了透镜受到衍射限制。回顾自1979年以来的文献研究，研究人员使用了不同的方法来补偿光轴的倾斜以获得理想的透镜，或者他们将本质上不对称的波前像差用作物理平面的自由形式光学器件。然而，尚未讨论轴倾斜背后的物理原理，就分子各向异性特性而言，LC透镜的倾斜光轴的起源尚待研究。在本文中，我们研究了LC透镜光轴的不对称倾斜的起源。我们发现，即使在旋转对称电场下，初始的各向异性分子倾斜（所谓的预倾角）也会导致介电转矩差。而且，发现即使电位是旋转对称的，也可以通过产生LC分子的不均匀的倾斜角来破坏波前的旋转对称。给出并讨论了数值结果以说明机理。