【作者】 蒋小平；

【导师】 刘德森；

【作者基本信息】 苏州大学 ， 凝聚态物理， 2011， 博士

【摘要】 生物复眼具有体积小、重量轻、视场角大、时间分辨率高等突出优点,微透镜阵列能充分发挥现代光学元器件向微型化、轻量化、阵列化、集成化和智能化方向发展的重要作用,将新型微透镜阵列研究与模仿生物复眼相结合,是微透镜阵列应用研究的热点之一,更是仿生学的重要研究课题。目前,国内外对仿复眼微透镜阵列的研究已经取得了阶段性成果,但在排列方式、材质、热稳定性、抗老化、抗机械应力或更完整地模仿生物复眼光学结构等方面仍有不同的局限。本文在对复眼光学结构分析的基础上,建立了一种复眼光学结构模型,进而提出并设计了一种采用光刻离子交换法制作的新型六角形孔径仿复眼曲面微透镜阵列,这种微透镜阵列具有孔径为六角形、填充率高、掩埋式、折射率呈三维梯度变化、基片为曲面、玻璃材质、微透镜元为一次性制作的“复合透镜”的特点,对已有仿复眼微透镜阵列存在的局限有一定突破。研究了对称的六角形开孔式Tl +- Na +离子扩散理论,利用扩散动力学分析了离子扩散区域相遇形成六角形边界问题,对在玻璃中形成折射率呈三维梯度变化的六角形孔径微透镜和具有凸透镜功能的开孔表面凸起进行了光学特性、成像特性分析,用矩阵光学的方法讨论了六角形孔径曲面微透镜阵列的光学特性。采用光刻离子交换法制作了仿复眼六角形孔径曲面型微透镜阵列,对其中的曝光掩模板的设计、基片制作、光刻、开孔蚀刻、离子交换等关键工艺进行了研究。在对玻璃材料的扩散特性测试的基础上,研究了中心距较大的六角形和圆形(为六角形内切圆)两种开孔的同温离子扩散特性,进而采用优化的方案,在曲率半径为250mm、直径为25mm的球面玻璃基片上成功制作了有2052个有效微透镜元的仿复眼六角形孔径曲面微透镜阵列。最后对制作的六角形孔径曲面微透镜阵列的形貌、曝光引起的开孔形变、多重成像、焦距、F数、球差、光斑、折射率分布等进行了观察、测试和分析,得到了如下结果:(1)采用光刻离子交换工艺,可一次性制作与复眼屈光器结构类似的六角形孔径曲面微透镜阵列;(2)当开孔设计为周期性六角形排列时,采用光刻离子交换工艺可以制作出边界为六角形的高填充率仿复眼微透镜阵列,但中心距相对较小的六角形开孔(相对于圆形开孔)是最佳的;(3)开孔式离子扩散的平均扩散速率、扩散系数因开孔形状、扩散方向不同而呈现不同的变化规律;(4)光刻离子交换法制作曲率半径较大(约为基片直径的20倍)的曲面微透镜阵列时,可以采用平面型曝光模板,图形形变率可忽略;(5)采用光刻离子交换工艺制作的曲面微透镜阵列多重成像质量、光学对称均匀性良好。焦距、F数自中心至边缘逐渐变小,数值孔径自中心向边缘逐渐变大,成像畸变较小,球差较为明显,聚焦性能较好,扫描光斑尺寸达4.92μm。此外,论文还提出了复眼时间分辨率、平面型掩模板对球面型基片曝光的形变率概念,并进行了分析;设计了一种简便的近似测量微透镜球差的方法。更多还原

【Abstract】 Compound eyes have some excellent features such as small size, light weight, big field angle of view and high time resolution. At the same time, microlens arrays play important roles in the development of modern optical systems advancing to micromation, lightweight, arraying, integrating and intelligentizing. To combine the novel microlens arrays and the simulation of compound eyes is one of the hot topics about microlens arrays and bionics. At the present time, phasic results have been obtained on microlens arrays simulated compound eyes, but it is limited in arrangement, material, thermal stability, corrosion resistance, anti-aging, responding to external stress or simulating whole optical functions of compound eyes.In this dissertation, based on analysis of optical structure of compound eyes, a model was founded. A method of fabricating a novel microlens array simulated compound eyes by photolithography and ion-exchange techniques is presented and designed. This kind of microlens with hexagonal aperture, high fill factor and gradient refractive index distributed in 3D is buried in a convex glass substrate, and each element of the microlens is a“compound lens”formed in a same process and in same time, which would breake the limitations of current ones in some aspects.The dissertation is focused on the diffusion theoretics of symmetrical apertured ion-exchange of Tl+-Na+, analysing the formation of hexagonal borders while the neighboring diffusion regions meet by theory of diffusion kinetics, analysis of optical and imaging characteristics of the microlens with hexagonal aperture and gradient refractive index in 3D and the bulge like a convex lens, and discussing the optical characteristics of the microlens array with hexagonal aperture buried in a convex substrate by method of matrix optics. Then a microlens array with hexagonal aperture and buried in a convex substrate was fabricated by photolithography and ion-exchange techniques including such key steps as design of a photomask, fabrication of the substrate, photolithography, etching apertures and ion-exchange. Firstly, the defusion characteristics of the glass used in the following fabrications was tested. Then, based on the testing results, the author studied the defusion characteristics of two samples with hexagonal and circular aperture, separately (The circle is just an incircle of the hexagon). Followed, a microlens array with hexagonal aperture and 2052 available microlenses was fabricated in a convex substrate with curvature radius of 250mm and diameter of 25mm. Finally, the appearance and cutting section of the microlens array, deformation in photolithography, multiple imaging, focal length, F number, spherical aberration, focused spot and distribution of refractive index is observed, measured and analyzed, then the following results are obtained.(1) A microlens array with hexagonal aperture and buried in a convex substrate simulated the dioptric apparatus of a compound eye can be fabricated by photolithography and ion-exchange.(2) A microlens array with high fill factor and hexagonal borders between any two neighboring microlenses can be made by photolithography and ion-exchange techniques if the designed apertures are arranged in hexagon symmetrically.(3) There are different laws in average deffusion rate, deffusion coefficient for different apertured shapes and in different directions.(4) A plane photomask can be suitable for a convex substrate when the photolithography and ion-exchange techniques are employed if the radius of curvature is big enough (20 times of the diameter of the substrate) to the size of the substrate. At the same time, the pattern deformations can be ignored too.(5) The microlens array fabricated by photolithography and ion-exchange techniques is every good in quality of multiple imaging, optical symmetry and uniformity. From center of the microlens array to the edge, the focal length and F number decrease a little gradually, but the NA increases. The spherical aberration of the microlens array is conspicuous and it can focus a laser beam into a spot of 4.92μm.Furthermore, some comcepts such as time resolution and deformation rate, a simple and convenient method of testing spherical aberration of microlens array are presented and discussed in the dissertation.更多还原