仿生复眼光学偏振传感器及其大气偏振E矢量检测应用

大气光学偏振模式中包含了丰富的方向和位置信息,通过提起大气偏振模式信息可以实现一种全新概念的自主导航定位方式,E矢量是其偏振信息中最为关键和最为稳定的参数。本文仿照昆虫的导航偏振敏感机理,设计了一种仿生复眼光学偏振传感器;根据昆虫的POL-神经元的信号处理方式,推导出传感器输出信号数学处理方法;对传感器进行了测试实验并在不同天气下对大气偏振模式中E-矢量方向进行检测。通过对实际的大气偏振模式进行检测,实现了误差小于0.46752°的偏振E矢量检测,对大气E-矢量的检测表明仿生复眼光学偏振传感器能够实现对大气偏振模式的准确检测,为偏振光导航这一自主导航系统发展奠定了基础。     

基于微流体芯片结构的PDMS二次倒模工艺研究

研究了用于制作微流体芯片结构的聚二甲基硅氧烷(PDMS)与PDMS之间的倒模方法。首先,通过使用同一个微流体芯片模具倒出多个相同的PDMS负模结构;接着分别在各负模结构上溅射不同种类、不同厚度的金属,然后再对溅射过金属的负模上浇铸PDMS并固化以进行二次倒模,最后对二次倒模出的PDMS微流体结构表面粘连、结构完整性、尺寸等进行观测,从而通过比较得到倒模溅射所需的最佳金属和溅射金属薄膜的最优厚度。此方法倒出的PDMS微流体结构完整性好,不仅提出了一种全新的用于PDMS倒模的方法,而且解决了PDMS与PDMS之间直接倒模时所遇到的相互粘连和结构撕裂等难题。     

仿蝇复眼视觉系统中大视场图像的拼接

针对现有图像拼接算法难以满足实时性的要求,模仿蝇复眼的视觉机理,设计一种仿生复眼视觉系统,用多个摄像头模仿蝇复眼中的小眼,提出直接拼接算法,对各个摄像头获得的图像进行合成,形成一大视场图像.实验证明:在保证图像拼接质量的同时,直接拼接算法消耗的时间仅为传统的图像拼接方法的2.6%,可见该方法快捷有效,具有更好的实时性能.     

大幅面3D打印边缘能量均匀化畸变消除

在基于掩膜投影的CLIP型3D打印工艺中,通过平铺多台投影设备扩大成型幅面时,重叠区域像素亮度的叠加产生的光学接缝会导致模型实体在该处产生畸变,影响成型质量。针对该问题提出一种边缘能量均匀化方案,通过非线性衰减的方式设计一组对称灰度虚拟掩膜,与相邻设备的切分掩膜图像相融合,矫正重叠区域的紫外光强,使整个印刷平面获得均匀且统一的紫外曝光能。实际打印结果表明,该方案能够有效改善模型实体在光固化成型中切片薄层固化厚度不均和拼接处易断裂的问题,模型实体整体质量有明显提高。     

中国微米纳米-微纳结构对电容式柔性压力传感器性能影响的研究

设计制备出三明治结构的电容式柔性压力传感器,并对其性能进行研究.该传感器以银纳米线为电极材料,聚二甲基硅氧烷(PDMS)为柔性衬底,同时采用毛面玻璃和光面玻璃分别作为柔性衬底的制备模板,制备出微纳结构和平面结构的PDMS薄膜.然后采用喷涂法制备AgNWs/PDMS复合电极,以另外一层PDMS为介电层,将两电极面对面封装,得到电容式柔性压力传感器,最后系统研究了传感器的电极微纳结构对器件性能的影响.本文研究表明,具有微纳结构的AgNWs/PDMS复合薄膜传感器的灵敏度为1.0 kPa-1,而平面结构的AgNWs/PDMS复合薄膜传感器的灵敏度为0.6 kPa-1,由此可知具有微纳结构的柔性衬底能够显著提高器件的灵敏度.     

亚波长纳米金属光栅偏振聚光器设计

为有效利用白天和夜晚的全天候偏振光信息,进一步拓展偏振光导航系统在微光环境下的应用,基于昆虫复眼的偏振视觉仿生原理,设计了一种亚波长光栅式平面金属聚光透镜结构,可以在保证偏振信息采集的同时实现微光环境中光的聚焦增强。基于表面等离子体激元光学理论,利用具有特定变化规律的变间距w和变高度d的纳米金属光栅阵列结构,设计了一种新型亚波长纳米金属光栅偏振聚光器。采用时域有限差分(FDTD)方法,对聚光器的结构参数进行了数值模拟,通过对聚光器光场分布的优化分析,给出了各参数对焦点位置和聚焦效果的影响规律,同时求解了TM光的透射率。其中最优结构的焦点位置位于偏振聚光器光出口2 798 nm,光强值提高到了16倍。在450 nm的偏振光导航器敏感波段其透射率约为63%。提出的新型金属光栅偏振聚光器结构为未来微纳偏振导航器件的光学设计与集成制造提供了有效的参考。     

仿生复眼成像仿真模拟

通过对仿生复眼成像机制的分析,建立了复眼偏歪成像的模型。应用焦点附近三维光场理论和偏歪成像模型仿真出了与复眼成像一致的像斑图像。仿真像斑较好地体现了实际像斑的基本特征。根据实际成像条件仿真的像斑可以为仿生复眼的聚焦特性改进和成像位置算法研究提供仿真依据。     

光学杠杆法测量电致伸缩材料应变研究

提出利用光学杠杆测量电致伸缩材料性能的新方法,通过触点短臂传感微形变,并通过光学杠杆将微形变放大后形成光斑,利用CCD摄像头采集放大前后的光斑,通过对光斑图像进一步的处理可以得到微位移量,从而实现电致伸缩材料应变测量.利用该方法构建的测试系统对掺杂了钛酸钡的聚氨酯高分子材料的电致伸缩性能进行了测量,结果表明:在高场强作用下,掺杂聚氨酯高分子材料表现出了明显的电致伸缩特性;光学杠杆法的测试系统能有效地测量包括电致伸缩微形变在内的微形变,同时为电致伸缩材料性能研究提供了一种方法.     

基于 ＧＮＰｓ/ ＰＤＭＳ 复合薄膜的柔性压阻传感器制备及性能研究

目前柔性压力传感器已被用于众多领域,其中压阻薄膜是柔性压力传感器的核心。本文将石墨烯纳米片（GNPs）与聚二甲基硅氧烷（PDMS）复合,通过倒模的方法制备压阻薄膜,经测试,GNPs浓度为8%时,材料具有较好的性能。以此为基础,制备了压敏结构间距为1.2 mm,直径大小为1.0 mm的GNPs/PDMS基压阻传感器,经测试,所制备的传感器加载响应为340 ms,卸载响应速度为260 ms,并具有较好的稳定性,同时,基于该压阻式柔性压力传感器实现了人体手腕关节处压力信号的测试。     

基于PDMS海绵介质层的电容式柔性压力传感器

柔性压力传感器以其低成本和大的检测范围等优势广泛的应用于电子皮肤和可穿戴传感器领域。本文通过在PDMS中填充碳酸氢铵材料,制备了大面积高密度具有微观结构的PDMS海绵介质层,通过简易的方法完成了柔性压力传感器的制备。与以往的柔性压力传感器相比,制备的PDMS海绵介质层由于气孔的存在更容易在受到压力时发生形变,拥有高的灵敏度(0.23 kPa^-1)、大的检测范围(0～50 kPa)、稳定的重复性(>1 000循环)以及快的响应时间(<150 ms)。通过对不同厚度、不同大小的PDMS海绵介质层进行测试,利用厚度为1.5 mm,大小为8 mm×8 mm的PDMS海绵作为压力传感器的介质层实现了力的实时检测。     

Fast replication of out-of-plane microlens with polydimethylsiloxane and curable polymer (NOA73)

Out-of-plane microlens, as its in-plane counterpart, is an important micro optics component that can be used in building integrated micro-optic systems for many applications. In earlier publications from our group, an ultra violet (UV) lithography based technique for out-of-plane microlens fabrication was reported. In this paper, we report a replication technology for time-efficient fabrication of out-of-plane microlens made of a curable polymer, NOA73. Microlens of cured SU-8 polymer was fabricated using a unique tilted UV lithography process, polydimethylsiloxane (PDMS) was molded using the resulting SU-8 master to form a negative mold, curable polymer NOA73 was then casted in the PDMS mold and out-of-plane microlens replica made of NOA73 was finally obtained after curing. The entire replication process took less than 5 h. Since PDMS negative mold was reusable, multiple replications of the microlens could be done with the same mold and each replication only took about 30 min. Scanning electron microscopic (SEM) images showed that NOA73 microlens replica had almost identical shape as the SU-8 master. In Comparison to the SU-8 microlens, microlens replica of UV curable polymer had slightly longer focal length and smaller numerical aperture due to the lower refractive index of NOA73. In addition, NOA73 microlens replica also had improved spectral transmission. Because of its compatibility with soft lithography technique, the reported replication process may also be used to integrate out-of-plane microlens into micro-opto-electro-mechanical-systems (MOEMS) and BioMEMS chips.     

Artificial compound eye: a survey of the state-of-the-art

An artificial compound eye system is the bionic system of natural compound eyes with much wider field-of-view, better capacity to detect moving objects and higher sensitivity to light intensity than ordinary single-aperture eyes. In recent years, renewed attention has been paid to the artificial compound eyes, due to their better characteristics inheriting from insect compound eyes than ordinary optical imaging systems. This paper provides a comprehensive survey of the state-of-the-art work on artificial compound eyes. This review starts from natural compound eyes to artificial compound eyes including their system design, theoretical development and applications. The survey of artificial compound eyes is developed in terms of two main types: planar and curved artificial compound eyes. Finally, the most promising future research developments are highlighted.     

Fabrication and Characterization of Three-Dimensional Microlens Arrays in Sol-Gel Glass

We propose a new replication process for the realization of thick microlenses in$ SiO_2$glass with low organic content. We start by replicating an array of cylindrical micropillars made in SU-8 negative photoresist (Microchem) into poly-dimethylsiloxane (PDMS). The PDMS replica is filled with a photoresist (Clariant AZ 9260), applied to a glass substrate and soft-baked. After demoulding, we obtain cylindrical pillars that are given a dome-like shape by a thermal softening. This structure is used as a master in a second PDMS replication step. An in-house developed sol-gel glass material with low organic content is then poured in the second PDMS replica and subsequently thermally treated to obtain an array of thick, dense and crack-free microlenses. We characterize the shrinkage and the surface roughness of the microlenses. Using imaging of millimeter-size objects in an optical microscope setup, we characterize basic optical properties of the lenses, like focal length, magnification, and distribution of the light intensity around the focal plane.1741     

Impact of oxygen-permeable mold on fabrication of microchannels with ultraviolet curable materials

In this work, effect of oxygen diffusion on curing of materials which are sensitive to ultra violet light (UV) in fabrication of microchannels using micromolds with oxygen permeability is investigated. The effects of physical boundary conditions of mold on microfabrication of polymeric arrays of high aspect-ratio microchannels in presence of oxygen inhibition and under variable UV intensity and dose are studied analytically and experimentally. Polydimethylsiloxane (PDMS) as the oxygen-permeable material and polyurethane methacrylate (PUMA) as the UV-curable substrate are selected for experiments. It is shown that for a wide range of exposure intensity and dose, a thin layer of PUMA resin with thickness of a few micrometers in contact with the mold remains uncured and inhibited by high concentration of oxygen molecules while the overall curing rate is reduced by about tenfold for PDMS compared to impermeable silicon mold. The direct impact of presence of high concentration of oxygen in both of mold and resin during UV curing and due to insufficient exposure dose and intensity is a considerable alteration in geometries of manufactured microstructures. The obtained results are crucial for method of use of micromolding and evaluation of fidelity of the replicated microstructures with the proposed design in terms of verticality of the walls and details of the transferring patterns that are important to microfluidic applications.

     

Norland optical adhesive (NOA81) microchannels with adjustable wetting behavior and high chemical resistance against a range of mid-infrared-transparent organic solvents

Different methods to adjust the wetting behavior of surfaces of the UV-curable adhesive NOA81 were investigated and quantitatively characterized by dynamic contact angle measurements with an optical goniometer. A new method to make NOA81 surfaces hydrophobic by mixing an additive in the uncured polymer was presented. The effect was confirmed by surface roughness studies using atomic force microscopy and X-ray photoelectron spectroscopy measurements. The chemical resistance of NOA81 microfluidic channels was evaluated by flowing organic solvents therein. Emphasis was placed on IR-transparent organic solvents. A simple, low-cost method to fabricate chemically resistant, hydrophilic, hydrophobic and hybrid (hydrophilic and hydrophobic), all-polymer microfluidic channels made of NOA81 was reported. Applications like oil-in-water and water-in-oil droplet generation or handling of a multi-phase flow were presented to demonstrate the chemical resistance and the control over the wetting behavior of NOA81 microfluidic chips.     

Non-visual biological effect of lighting and the practical meaning for lighting for work

The effects of good lighting extend much further than we used to think. Recent medical and biological research has consistently shown that light entering the human eyes has, apart from a visual effect, also an important non-visual biological effect on the human body. As a consequence, good lighting has a positive influence on health, well-being, alertness, and even on sleep quality. Our better understanding of the diversity in lighting effects teaches us that new rules governing the design of good and healthy lighting installations are required. Thanks to the recent discovery of a novel photoreceptor in the eye and its probable distribution within the eye we can now begin to define these new rules. These will guide us to dynamic lighting installations: that is to say dynamic in lighting level and dynamic in tint of whiteness of the lighting colour.     

聚二甲基硅氧烷微流体芯片的制作技术

基于MEMS技术的微流体芯片在分析化学和生物医学领域显示了巨大的应用潜力。作为构建微流体芯片的基底材料———聚二甲基硅氧烷(PDMS)已经表现出了许多的优点:良好的电绝缘性、较高的热稳定性、优良的光学特性以及简单的加工工艺等。采用浇注法制作了PDMS电泳微芯片,对PDMS微流体芯片的加工工艺、封装方法和结构特征进行了探讨,并提出了相应的解决方案。     

Linear Quasi-Parallax SfM Using Laterally-Placed Eyes

A large class of visual systems in the biological world often has multiple eyes in simultaneous motion and yet has little or no overlap in the visual fields between the eyes. These systems include the lateral eyes found in many vertebrates and the compound eyes in insects. Instead of computing feature correspondences between the eyes, which might not even be possible due to the lack of overlap in the visual fields, we exploit the organizational possibility offered by the eye topography. In particular, we leverage on the pair of visual rays that are parallel to each other but opposite in direction, and compute what we call the quasi-parallax for translation recovery. Besides resulting in parsimonious visual processing, the quasi-parallax term also enhances the information pick-up for the translation, as it is almost rotation-free. The rotation is subsequently recovered from a pencil of visual rays using the individual epipolar constraints of each camera. As a result of using these different and appropriate aspects of visual rays for motion recovery, our method is numerically more effective in disambiguating the translation and rotation. In comparison to the gold standard solution obtained by the bundle adjustment (BA) technique, our method has a better Fisher information matrix for a lateral eye pair, as well as a superior experimental performance under the case of narrow field of view. For other eye configurations, the two methods achieve comparable performances, with our linear method slightly edging the nonlinear BA method when there exists imperfection in the calibration.     

一种基于几何分布的新支持向量机多分类方法

二叉树支持向量机是多分类问题的一种有效方法,然而分类的效果与二叉树的结构密切相关。获得更好的分类效果和更高的效率,要使得二叉树高度尽量小而两个子类尽量易分。距离通常用来衡量两个类的分离程度,但不能反映类的分布情况。考虑到多分类中类的分布,文中定义新的分离度和相似度来衡量两个类的分离度,并且提出了一中新的基于几何分布二叉树支持向量机多分类算法,该方法使得二叉树高度尽量小而两个子类尽量易分。实验表明该方法具有较高的分类准确率和效率。     

In-situ fabrication of an out-of-plane microlens with pre-definable focal length

Out-of-plane microlenses are an important component for integrated optics. Unlike their in-plane counterparts, the fabrication of out-of-plane microlenses is more complicated, which limits their applications. In this paper, a new technique that is capable of fabricating out-of-plane microlenses is described. The resulting lenses have pre-definable focal length and can focus light beams not only in the horizontal plane, but also in the vertical plane. The fabrication process is completely compatible with the soft lithography technique. The lens chamber with two thin polydimethylsiloxane (PDMS) membranes was designed and fabricated together with microfluidic or other components using the same UV lithography mask. The lens was then formed in an in-situ fashion. Curable polymers were injected into the lens chamber and cured while pneumatic pressure was applied to keep the PDMS membranes deformed in a quasi-spherical profile. Pneumatic pressure and membrane thickness can be adjusted to control the resulting lens focal length. With a group of lens chambers with different membrane thickness, a single pressure line can be used to fabricate microlenses with different focal lengths. Since cured polymer was used as the lens filling material, the resulting lens can be used without a pressure source. Different polymers can be selected for desirable optical properties. The simulation and experimental results have proved the feasibility of this technique and resulting lens showed good focusing ability for a divergent light beam from an on-chip multi-mode optical fiber. The small design footprint, total compatibility with soft lithography and technical versatility of this technique make it particularly useful for intergrating out-of-plane microlens into microfluidic chips, which may open new possibilities for the development of on-chip optical detection system.