Application of eigenmode in the adaptive optics system based on a micromachined membrane deformable mirror

The construction process and characteristics of a deformable mirror eigenmode are introduced. The eigenmode of a 37-element micromachined membrane deformable mirror (MMDM) from OKO, Ltd. is analyzed. The Gaussian-Seidel low-order aberrations are fitted with eigenmodes as basic functions. An experimental adaptive optics (AO) system is constructed with the MMDM as the wavefront corrector, a deformable mirror eigenmode as the wavefront control algorithm, and a Shack-Hartmann wavefront sensor as the wavefront detector. The experimental results demonstrate that the deformable mirror eigenmode can act as the wavefront control algorithm for the AO system based on the MMDM.     

Adaptive control of a micromachined continuous-membrane deformable mirror for aberration compensation

The nonlinear response and strong coupling of control channels in micromachined membrane deformable mirror (MMDM) devices make it difficult for one to control the MMDM to obtain the desired mirror surface shapes. A closed-loop adaptive control algorithm is developed for a continuous-surface MMDM used for aberration compensation. The algorithm iteratively adjusts the control voltages of all electrodes to reduce the variance of the optical wave front measured with a Hartmann-Shack wave-front sensor. Zernike polynomials are used to represent the mirror surface shape as well as the optical wave front. An adaptive experimental system to compensate for the wave-front aberrations of a model eye has been built in which the developed adaptive mirror-control algorithm is used to control a deformable mirror with 19 active channels. The experimental results show that the algorithm can adaptively update control voltages to generate an optimum continuous mirror surface profile, compensating for the aberrations within the operating range of the deformable mirror.     

微机械薄膜变形镜的闭环校正模型

介绍了微机械薄膜变形镜(MMDM)面形影响函数的意义,并测量了Oko公司37通道MMDM的面形影响函数矩阵,实验验证了镜面形变和单个驱动电极电压平方之间的线性关系,分析了变形镜的校正能力,建立了自适应光学系统闭环校正的模型.搭建基于MMDM的自适应光学实验系统,采用人眼出射波前作为原始波前进行实验,结果表明,模型能快速有效的对动态畸变波前进行校正,为基于MMDM的自适应光学系统提供了算法支持.     

自适应光学系统MEMS微变形镜的研究

指出了传统变形镜研究所面临的瓶颈，以及采用MEMS技术研究微变形镜的优点．介绍了利用静电力驱动的平板电容式分立式微变形镜．分析结果表明它具有比传统变形镜更优越的性能．指出了进一步研究与发展MEMS微变形镜还需要解决的若干重要问题．     

大行程变形镜有限元分析

针对自适应光学系统对变形镜行程的更高要求,本文对提高变形镜行程技术进行了分析,提出了一种解决变形镜大行程的方法:匹配、优化变形镜的结构参数;利用有限元软件分析了该结构的各参数对变形镜主要性能指标:最大变形量、交连值及最大应力等的影响.根据分析结果,利用有限元分析方法对一自适应光学望远镜所用变形镜的镜面、驱动器结构参数进...     

The influence of high-frequency phase and correction distance on the phase correction effect

By studying the propagation characteristics of the wavefront phase of laser beams in adaptive optics systems, the influence of the high-frequency phase on the correction effect has been analyzed and the variations of correction effect with the position of optical deformable mirror have been analyzed quantitatively. The results show that the beam quality of the corrected beam in far field obviously degrades with an increase of high-frequency phase in a distorted wavefront, and the correction effect becomes worse and worse. In addition, the correction effect is related to the position of the deformable mirror; with an increase of the distance between the deformable mirror and the output mirror of the laser the correction effect is better. For a deformable mirror with a given unit size, when the distance of correction is more than 20?m the correction effect is perfect.     

微机械薄膜变形镜光学影响函数矩阵的测试与研究

介绍了微机械薄膜变形镜光学影响函数的理论表达式以及其具有的线性叠架性，对OKO公司的37通道微机薄膜变形 进行了实际测量，得到了光学影响函数矩阵，方便了变形镜实际使用，实验结果验证了理论推导的正确性。     

新型静电驱动双向平动MEMS变形镜(英文)

设计了一种新型静电驱动双向平动的MEMS变形镜,其结构包括3部分:中央下电极,4个静电驱动杠杆结构以及反射镜面(上电极).该变形镜有两种驱动模式:向下驱动模式和向上驱动模式.在向上驱动时,4个杠杆结构实现了位移的放大;向下驱动时,利用了非线性弹性系数法扩展了镜面的平动范围.采用表面硅工艺完成了变形镜的加工.通过白光干涉仪对变形镜的测试表明:在向上驱动模式下,变形镜在驱动电压为31 V时位移达到1.1μm;在向下驱动模式下,变形镜在6 V的驱动电压下位移达到1.1μm.变形镜的总行程为2.2μm,达到了同样工艺下传统变形镜的3倍左右.     

Aberration-free dynamic focusing with a multichannel micromachined membrane deformable mirror

We demonstrate aberration-free dynamic focusing with a low-cost 19-channel continuous-surface micromachined membrane deformable mirror (MMDM). A lookup table of the optimum control voltages for various focal lengths is obtained with an adaptive optics algorithm. Diffraction-limited imaging resolution is achieved owing to the capablility of the MMDM for aberration compensation. The measured speed of the MMDM supports dynamic focusing operations at several hundred hertz. Our dynamic focusing approach is shown to function with either monochromatic or broadband optical sources.     

Variable zoom system with aberration correction capability

We describe experiments conducted with two deformable mirrors (DMs) at fixed locations in an optical microscope imaging system. In this configuration, the DM shapes are controlled to provide 2.5× zoom capability, to allow dynamic focus control and to compensate for aberrations of the fixed optical components. Zoom is achieved by simultaneously adjusting focal lengths of the two DMs, which are inserted between an infinity-corrected microscope objective and a tube lens. Image quality is measured using contrast modulation, and performance of the system is quantified, demonstrating an improved point spread function in the adaptively compensated system.     

压电厚膜驱动的高刚度微变形镜的制备

研究制备了一种压电厚膜微变形镜,微变形镜的连续薄膜式单晶硅镜面由61单元压电厚膜致动器阵列驱动.以镜面冲程与工作频带宽为目标,对微变形镜的结构参数进行优化设计,根据优化参数采用硅微加工技术试制了61单元致动器的微变形镜.镜面、压电陶瓷与弹性支撑层厚度分别为100μm、60μm与60μm,单元间距为5mm,通光口径为40 mm.对制备的样品性能进行了测试,微变形镜在100 V电压驱动下变形量约为2.84μm,工作带宽大于10 kHz.测试结果还表明压电厚膜驱动的微变形镜拥有较高刚度,有利于提高镜面初始平面度.     

基于锆钛酸铅薄膜的变形镜微致动器

以锆钛酸铅（PZT）薄膜作为驱动材料,制备了变形镜的微致动器阵列．使用有限元软件对致动器进行了模拟仿真,得到了驱动器上电极尺寸、Si弹性层厚度等参数对致动器性能的影响,获得了最优化的致动器结构．以钙钛矿相的镍酸镧（LNO）作为PZT薄膜在Pt衬底上生长的缓冲层,增强了PZT薄膜的（100）取向,减小了PZT薄膜的内部应力,提高了致动器的驱动性能．最终制备出的1μm厚PZT薄膜驱动的变形镜微致动器,在10V直流电压的激励下,具有2．0μm的变形量．以PZT薄膜作为驱动材料制备的变形镜微致动器阵列,对变形镜致动器的微型化和系统集成度的提高具有重要意义．     

Development of a new technology of deformable mirror for ultra intense laser applications

Adaptive optics is now a standard feature for the current ultra high intensity lasers facilities. Aberration induced by both the optical components and the thermal effects in the amplification stages can be corrected with an adaptive optics system to reach both maximum peak energy and fluence. In this article, we present the development of a new technology of deformable mirror. These mirrors are designed taking into account the needs and specificities of ultra intense laser applications. They provide exceptional stability, optical quality and innovative features like scalability and maintenance of the reflective surface.     

Optimal wave-front reconstruction strategies for multiconjugate adaptive optics

We propose an optimal approach for the phase reconstruction in a large field of view (FOV) for multiconjugate adaptive optics. This optimal approach is based on a minimum-mean-square-error estimator that minimizes the mean residual phase variance in the FOV of interest. It accounts for the C2n profile in order to optimally estimate the correction wave front to be applied to each deformable mirror (DM). This optimal approach also accounts for the fact that the number of DMs will always be smaller than the number of turbulent layers, since the C2n profile is a continuous function of the altitude h. Links between this optimal approach and a tomographic reconstruction of the turbulence volume are established. In particular, it is shown that the optimal approach consists of a full tomographic reconstruction of the turbulence volume followed by a projection onto the DMs accounting for the considered FOV of interest. The case where the turbulent layers are assumed to match the mirror positions [model-approximation (MA) approach], which might be a crude approximation, is also considered for comparison. This MA approach will rely on the notion of equivalent turbulent layers. A comparison between the optimal and MA approaches is proposed. It is shown that the optimal approach provides very good performance even with a small number of DMs (typically, one or two). For instance, good Strehl ratios (greater than 20%) are obtained for a 4-m telescope on a 150-arc sec x 150-arc sec FOV by using only three guide stars and two DMs.     

Deformable liposomes by reverse-phase evaporation method for an enhanced skin delivery of (+)-catechin

Background: (+)-catechin, as the most common catechin isomer, is recognized to be an antioxidant which benefits the skin in many ways. The purpose of the present study was to prepare and evaluate a suitable liposomal delivery systems for (+)-catechin topical application.

Methods: In this study, catechin-loaded conventional liposomal delivery system, deformable conventional liposomal delivery system and deformable liposomes prepared by reverse-phase evaporation (REV) method were compared. The three systems were characterized for liposome particle size, zeta-potential, entrapment efficiency, drug release, permeability across porcine skin and catechin deposition in the skin.

Results: It was revealed that the size of deformable conventional liposomes before freeze-drying and deformable REV liposomes after freeze-drying range from 335.6?±?71.7?nm to 551.1?±?53.4?nm, respectively, which were considered to be suitable for skin delivery. The deformable REV liposomes had a higher aqueous volume and thus were able to entrap greater amounts of hydrophilic (+)-catechin (50.0?±?5.9%) compared to conventional (30.0?±?3.8%) and deformable conventional liposomes (36.1?±?4.6%). All liposomal formulations exhibited a prolonged catechin release. Compared to deformable liposomes, the REV deformable liposomes showed a significantly better deposition of (+)-catechin while catechin solution did not permeate into the porcine ear skin.

Conclusion: Among all formulations studied, deformable REV liposomes were considered to be favorable for catechin topical delivery.     

Wave-front generation of Zernike polynomial modes with a micromachined membrane deformable mirror

We investigate the characteristics of a 37-channel micromachined membrane deformable mirror for wave-front generation. We demonstrate wave-front generation of the first 20 Zernike polynomial modes, using an iterative algorithm to adjust driving voltages. The results show that lower-order-mode wave fronts can be generated with good accuracy and large dynamic range, whereas the generation of higher-order modes is limited by the number of the actuator channels and the working range of the deformable mirror. The speed of wave-front generation can be as fast as several hundred hertz. Our results indicate that, in addition to generation of wave fronts with known aberrations, the characteristics of the micromachined membrane deformable mirror device can be useful in adaptive optics systems for compensating the first five orders of aberration.     

Adaptive Control of a Micromachined Continuous Membrane Deformable Mirror for Aberration Compensation

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Rollable,Stretchable, and Reconfigurable Graphene Hygroelectric Generators

Moisture‐triggered electricity generation has attracted much attention because of the effective utilization of the water‐molecule diffusion process widely existing in atmosphere. However, the monotonous and rigid structures of previously developed generators have heavily restricted their applications in complex and highly deformable working conditions. Herein, by a rational configuration design with a versatile laser processing strategy, graphene‐based hygroelectric generators (GHEGs) of sophisticated architectures with diversified functions such as rollable, stretchable, and even multidimensional transformation are achieved for the first time. More importantly, a wide range of 3D deformable generators that can automatically assemble and transform from planar geometries into spacial architectures are also successfully fabricated, including cubic boxes, pyramids, Miura‐ori, and footballs. These GHEGs demonstrate excellent electricity‐generation performance in curling and elongating states. The generated voltages are easily up to 1.5 V under humidity variation in atmosphere, powering a variety of commercial electronic components. These deformable GHEGs can be applied on complicated surfaces, human bodies, and many more beyond those demonstrated in this work.     

一种新型微变形镜键合技术

对一种新型可变形反射镜加工中的硅-玻璃阳极键合工艺进行了研究。设计了一种通过导线将压焊点引至键合区的特殊结构,使得键合过程中台柱与驱动电极保持等电势,从而有效避免了电极和结构之间的相互作用所引入的缺陷,使得最终获得的驱动电极的有效面积接近100%。针对键合前后气体体积收缩导致的镜面凹陷问题,提出在玻璃上加工出贯穿器件的浅槽结构。实验结果表明,在380C,1atm的环境下施加-1000V电压进行阳极键合时,当浅槽深度大于200nm时,将获得较好的镜面质量。     

Bimorph变形镜10.6μm薄膜研究

基于压电驱动器的Bimorph变形镜是10.6 μm系统的一个重要元件.为了镀制薄膜,本文首先利用有限元软件对两种镀膜夹持方式与沉积温度进行了计算,对热应力产生的热变形进行了分析,选择了合适的镀膜夹持方式.为了预测bimorph变形镜受激光辐照后的温升,对单晶硅与石英玻璃制作的bimorph变形镜有限元模型进行了计算与分析.最后,利用光度计对镀制的薄膜进行了反射率测量.试验结果显示反射率测量值大于99.5％,满足实际系统的需要.