基于固态可调焦透镜的短焦大视场微型光学变焦系统机理及优化方法研究

Miniature optical zoom systems with short focal length and wide field of view have diverse applications in modern portable and wearable electrical devices. Conventional optical zoom systems face the problems of bulky structures and complicated supporting and driving mechanisms, which greatly limit their applications in miniature systems. Liquid, as well as liquid crystal, lenses bring us the possibility of miniature applications, but also a series of practical problems, including instability, hysteresis and limited tuning ranges. Solid tunable lenses that we proposed recently show a great potential to solve these problems by using freeform optical devices assisted with micro/miniature actuators. However, miniature optical zoom systems involving such solid tunable lenses face the problems of limited optical power and field of view, image plane shift, unbalanced image quality and coupling effect between optical, mechanical, and electrical fields. The inherent reasons leading to these problems are not clear. This project firstly establishes the physical model of the miniature optical zoom systems using the vector aberration theory, based on which the law of imaging, aberration characteristics, optical surface describing methods and effect of misalignments on system performance are systematically studied. Furthermore, the key factors limiting the increase of optical power and field of view, as well as the inherent reasons leading to the image plane shift, unbalanced image quality and coupling effect between optical, mechanical, and electrical fields, are analyzed thoroughly. Subsequently, the design methodology and rules of such non-rotational-symmetric miniature optical zoom systems, together with the optimization methods of the coupling mechanism between optical, mechanical, and electrical fields are studied. This project can benefit related fields with solid foundation, enriched methodologies

短焦大视场微型光学变焦系统在便携式及可穿戴电子设备上应用前景广阔。传统光学变焦系统结构复杂、体积臃肿，难以实现微型化应用，而液体或液晶透镜稳定性差、迟滞明显、变焦范围有限，难以达到实用要求。我们近期提出的基于自由曲面器件和微型驱动器的固态可调焦透镜有望解决这些问题。然而，研究发现，基于此类可调焦透镜的微型光学变焦系统在提高光焦度和增大视场上面临困难，同时暴露出了像面漂移、像质不均衡、光机电耦合影响等问题，其内在机理尚不清楚。课题基于矢量像差理论建立该非旋转对称微型光学变焦系统的物理模型，研究连续动态变焦情况下系统的成像规律、像差特性、最优面型描述方法及器件公差与装配误差的影响机理，揭示制约光焦度提高和视场增大的核心因素，理清产生像面漂移、像质不均衡、光机电耦合影响等问题的根本原因，进而建立此类系统的光学及光机电综合优化设计方法和准则，为相关研究夯实基础、丰富手段、拓宽思路，具有重要意义。

围绕“如何利用光学自由曲面器件和微型驱动器实现符合实用要求的短焦大视场微型光学变焦系统”这一核心问题，项目开展了固态可调焦透镜及微型光学变焦系统物理机理、复杂边界条件约束下非旋转对称微型光学变焦系统设计方法、几何工艺材料关联约束下微型光学变焦系统综合优化设计和微型光学变焦系统成像质量与变焦能力试验测试与评估四个方面的研究。.研究表明，基于自由曲面的固态变焦系统实现光学变焦的原理是利用微型驱动器精确控制光学组件的横向位移，进而改变其等效光学相位延迟，以实现不同的光焦度；连续动态变焦情形下，固态变焦系统的成像性能随光学组件的横向位移增大而逐渐劣化，减小三阶项系数有助于改善这一现象；自由曲面面型最优描述方法为XY高阶多项式，且在初始值选取时，其三阶项系数应在满足调焦范围的前提下尽量小，一阶项系数应使得两个光学组件之间的空气间隙最小；优化设计过程中，视场参数需至少覆盖子午面、弧矢面以及两面的45°夹角面以克服非旋转对称性带来的问题；优化函数需逐步增加以避免局域最优解，先优化点图及光线像差，再逐步增加成像性能约束和衍射性能约束，同时视场逐步增大，按照光轴旋转对称均匀分布，以实现全视场内的性能均衡控制；影响系统性能的误差包括组件相对位移、倾斜及旋转，其中相对运动方向的位移对性能的影响最为剧烈；设计了基于微型压电片和MEMS电热驱动器的驱动结构，基于对称V形四臂位移放大结构可分别实现约16倍和10倍的位移放大，两者动态响应时间分别在毫秒和百毫秒量级；基于固态可调焦透镜的水下变焦成像模块可实现对不同物距处目标的清晰成像，达到25线对每毫米的分辨率，可基本满足常见光学成像系统的要求。.课题揭示了固态可调焦透镜的变焦机理，理清了像面漂移、像质不均衡、光机电耦合影响等问题的原因，提出了此类系统的光学及光机电综合优化设计方法和准则，相关成果可为后续研究夯实基础、丰富手段、拓宽思路，具有重要意义。