纯相位液晶空间光调制器拟合泽尼克像差性能分析

纯相位液晶空间光调制器作为波前校正器构成的高分辨率、低能耗、价格低廉、易于控制的自适应光学系统受到越来越多的关注.作为一种新型波前校正器件,它对波前像差的校正能力是反映其在自适应光学系统中应用的一个重要的指标,因此有必要仔细地研究它对各种像差的校正能力,以确定其可能的应用范围.波前校正器对各阶泽尼克像差的拟合效果有效地反映了该器件对不同像差的校正能力.利用256×256像素的纯相位液晶空间光调制器(LC-SLM)产生不同系数的前36项泽尼克像差分析LC-SLM对不同像差的校正能力.讨论了填充因子、离散像素 关键词： 液晶空间光调制器 相位调制 自适应光学 泽尼克多项式     

光镊轴向阱位操控及器件安装误差对径向阱位操控的影响

光镊利用光学梯度力捕获和操控微小粒子,已经成为深入研究生物分子间相互作用等微观机制的独特技术.光镊光束操控系统一般由扩束输入镜、扩束输出镜、调焦透镜、耦合透镜和压电转镜等光学元器件组成,以保证物镜后瞳充满的前提下实现光镊阱位操控.光镊阱位的三维精确操控是实现光镊位钳和力钳模式的基本条件.本文根据矩阵光学,对基于无穷远校正显微镜的光镊操控光路进行计算,分析扩束输入镜、调焦透镜和物镜轴向位置调整,以及压电转镜、调焦透镜和耦合透镜安装位置误差对光镊径向阱位操控精度的影响,得到了物镜高度调整基本不会影响光镊径向位置操控,压电转镜和调焦透镜的安装位置误差对光镊径向阱位操控精度影响最大等结论,提出了能够实现径向阱位精确操控的轴向阱位动态操控范围,为光镊设计和操控提供理论和实验指导.     

用空间光调制器产生三维光阱阵列

本文提出了用液晶空间光调制器制作复合相位光栅、产生三维光阱阵列的新方案．在本方案中,首先将一维矩形光栅转变为能够产生纵向光阱阵列的环形光栅,再把环形光栅和二维矩形光栅组合成复合光栅．根据现有空间光调制器的技术参数,模拟仿真设计了产生5×5×5光阱阵列的光栅,以普通功率的高斯光波为输入光,正透镜聚焦衍射光,计算输出光强分布,结果表明：在透镜焦点附近获得具有很高峰值光强和光强梯度的三维光阱阵列,囚禁冷原子的光学偶极势达到mK量级,对原子的作用力远大于原子的重力．用大功率激光作为输入光波时,产生的光阱阵列也能用于囚禁Stark减速后的冷分子．     

轴向多光阱微粒捕获与实时直接观测技术

传统的光镊技术使用单个物镜同时进行光学捕获与显微成像,使得捕获与成像区域被限制在物镜焦平面附近,无法同时观察到沿光轴方向(即Z向)捕获的多个微粒.本文提出一种轴平面(XZ平面)GerchbergSaxton迭代算法来产生沿轴向分布的多光阱阵列,将轴平面成像技术与光镊结合,实现了沿轴向对二氧化硅微球的多光阱同时捕获与实时观测.通过视频分析法测量了多个二氧化硅微球在轴向光镊阵列中的布朗运动,并标定了光阱刚度.本文提出的轴向多光阱微粒捕获与实时观测技术为光学微操纵提供了一个新的观测视角和操纵方法,为生物医学、物理学等相关领域研究提供了一种新的技术手段.     

纯相位液晶空间光调制器拟合泽尼克像差性能分析

纯相位液晶空间光调制器作为波前校正器构成的高分辨率、低能耗、价格低廉、易于控制的自适应光学系统受到越来越多的关注.作为一种新型波前校正器件，它对波前像差的校正能力是反映其在自适应光学系统中应用的一个重要的指标，因此有必要仔细地研究它对各种像差的校正能力，以确定其可能的应用范围.波前校正器对各阶泽尼克像差的拟合效果有效地反映了该器件对不同像差的校正能力.利用256×256像素的纯相位液晶空间光调制器(LC-SLM)产生不同系数的前36项泽尼克像差分析LC-SLM对不同像差的校正能力.讨论了填充因子、离散像素     

有限远共轭显微镜光镊设计和误差分析

光镊是研究单分子生物物理特性的独特工具, 因而光镊设备的研发是一个极为重要的课题. 本文根据矩阵光学, 对基于有限远共轭显微镜的光镊操控光路进行计算, 得出了阱位径向操控和轴向操控方程, 并分析了光束调控系统、 共焦系统后置透镜和耦合透镜安装位置误差及物镜轴向位置调整对光镊阱位径向及轴向操控精度的影响. 计算结果显示, 当物镜初级像面和耦合透镜像方焦面完全重合, 光束调控系统和耦合透镜的距离误差对阱位径向和轴向操控精度没有影响. 光镊系统元器件定位不准时, 基于无限远共轭显微镜光镊的阱位径向操控误差和轴向操控误差都小于基于有限远共轭显微镜光镊的阱位径向操控误差和轴向操控误差. 当光镊耦合透镜定位误差控制在小于10 mm时, 基于有限远共轭显微镜光镊的径向和轴向操控误差分别小于5.9%和11.4%, 有限远共轭显微镜仍然存在改造为光镊的价值.本文理论为基于有限远共轭显微镜的光镊设计、改造和操控提供理论和实验指导. 关键词： 光镊 光学设计 矩阵 误差     

基于低损光学相变和超透镜的可控多阱光镊

为提升光镊在三维空间中对粒子的捕获性能,本文设计和分析了新型的双阱和多阱超透镜光镊方案.首先基于低损耗相变材料Sb₂S₃设计了可控超透镜双阱光镊,并对两个半径为250 mm的SiO₂粒子所受光力进行了矢量横向分析和轴向分析.仿真实验结果表明,当Sb₂S₃在晶态下时,超透镜捕获的两个粒子的横向光阱刚度k_x分别达到了约25.7 pN/(μm·W)和37.4 pN/(μm·W),轴向光阱刚度k_z均约为10.0 pN/(μm·W);而当Sb₂S₃在非晶态下时,k_x和k_z值均降低到其对应晶态下的1/10,且此时粒子在z方向上不能被稳定捕获,从而实现了在三维空间中对粒子的可控捕获.进一步本文给出了阵列式的可控多阱光镊.通过调控相变材料Sb₂S₃的晶态和非晶态,能形成不同组合粒子的三维捕获方案.这些新型可控光镊可实现多...     

共光路共模块自适应光学系统中赝相位共轭器件应用分析

研究了角反射器阵列形成赝相位共轭波的能力,计算了其对泽尼克多项式表示的各阶像差的保真度,分析了在共光路共模块自适应光学系统中角反射器阵列与哈特曼－夏克波前传感器二者之间单元数目,位置匹配方面的问题,对失配所带来的误差进行了计算。     

基于视觉原理和流体力学法的全息光镊三维光阱刚度测量

为了检测全息光镊的捕获能力,将基于视觉原理的光学测量系统用于全息光镊三维光阱刚度的测量.光学系统采用对称分布的双光源照射样品池,形成两个像点,通过跟踪像点位移获取被全息光镊捕获微球的三维位移信息.结合流体力学法测出本光学系统中单、双光阱的三维光阱刚度.实验结果表明:单光阱中,沿X、Y水平方向光阱刚度相差不大,而轴向光阱刚度落在水平方向的1/3~1/4范围;双光阱中,离光轴(即衍射中心)近的光阱其三维刚度要比距离光轴稍远的光阱要大,说明越靠近衍射中心,光的衍射效率越高,产生的光阱捕获能力也越强.     

共轭读出法消除光致变色材料全息记录中的相位畸变

采用有机光致变色材料-吲哚俘精酰胺/PMMA薄膜作为可擦写全息记录介质,建立了一种能消除全息光存储中相位畸变的光路.此光路采用参考光的相位共轭光再现全息图,能有效消除物光路中由于光学元件失调和记录材料缺陷引起的相位畸变,是全息光存储中提高再现像像质的一种有用光路.     

基于固定校正板和透镜阵列的机载共形窗口像差校正

为了校正大扫描视场机载共形窗口引入的像差,提出一种基于固定校正板和透镜阵列的静态校正方法。首先使用固定校正板校正静态像差;然后在像面前安置固定的透镜阵列,利用透镜阵列中的各个透镜单元分别校正不同扫描角度的动态像差;最后基于所提方法设计应用在机载共形光学系统中的像差校正器。设计结果表明,所提方法在±42°的扫描视场范围内能够良好地校正共形窗口引入的像差。与其他动态或静态校正方法相比,所提方法可以实现大扫描视场机载共形光学系统像差的校正,同时降低机载共形光学系统的质量,提高系统的稳定性。     

Vision improvement by correcting higher-order aberrations with customized soft contact lenses in keratoconic eyes

Higher-order aberration correction in abnormal eyes can result in significant vision improvement, especially in eyes with abnormal corneas. Customized optics such as phase plates and customized contact lenses are one of the most practical, nonsurgical ways to correct these ocular higher-order aberrations. We demonstrate the feasibility of correcting higher-order aberrations and improving visual performance with customized soft contact lenses in keratoconic eyes while compensating for the static decentration and rotation of the lens. A reduction of higher-order aberrations by a factor of 3 on average was obtained in these eyes. The higher-order aberration correction resulted in an average improvement of 2.1 lines in visual acuity over the conventional correction of defocus and astigmatism alone.     

Self-aligned imaging system using phase conjugate readout from elementary holographic grating

We propose a self-aligned imaging system (SAIS) using phase conjugate readout from an elementary holographic grating. The SAIS provides a huge amount of interconnections between a lot of points on two corresponding imaging planes without troublesome mechanical alignment. In the SAIS, a hologram for one-to-one interconnection is used for many-to-many interconnections. In addition, the SAIS has the capability of correcting aberration. Preliminary experiments verify the principle and the capability of the SAIS.     

Pickup lens inspection on the 5th order aberration using shearing interference by grating with curve fitting algorithm

An optical system based on shearing interference using diffraction grating was applied, to carry out the aberration inspection process of the pickup lens of a digital versatile disc (DVD) at high speed. An algorithm was devised that processes points allocated on certain lines on a fringe and fits relations between the distance from basis point to the measurement points, and phase data of the fringe at these points to an equation of higher degree as curve fitting. Aberration was numerically estimated as the size of a certain coefficient. Simulation showed that this algorithm could detect all 5th order aberrations independently. An inspection system developed based on this optical system and algorithm detected aberration as accurately as a conventional interferometer that has been used as the standard, attaining an inspection time of 1/10-1/20. In comparison with the spot method, this system has 5th order aberration detecting ability and 1/3 the inspection time.     

Simulation of Differential Phase Detection Method Combined with Astigmatic Method using a Half Mirror in an Optical Pick-up

In an error detection optical system for optical pick-ups using a parallel plane type half mirror, influence on the differential phase detection (DPD) signal by a coma aberration was simulated. The coma aberration deforms the spot profile on the photodetector and influences the DPD signal level characteristics and the offset characteristics with respect to the objective lens shift. In the 4-segment-type DPD, the coma aberration caused by a half mirror 2.75 mm thick hardly affects the DPD signal if the photodetector is not misaligned. On the other hand, the 2-segment-type DPD has a small offset variation with respect to the objective lens shift and a large variation of the DPD signal level against the misalignment of the photodetector in comparison with the 4-segment-type DPD when there is no coma aberration. In the presence of a coma aberration, however, these variations of the 2-segment-type DPD are suppressed by choosing a pair of elements without the coma apex part of the spot.     

Optimum holographic optical element lens recorded by visible laser beams for an infrared two-dimensional vertical-cavity surface-emitting laser array

We have designed an optimum holographic optical element (HOE) lens recorded by visible laser beams for an infrared two-dimensional vertical-cavity surface-emitting laser (VCSEL) array. The hologram computer-aided design tool that we have developed is used for the optimum design. The optimum HOE has both high light efficiency and a small amount of aberration. An Nd:YAG laser operated at 532 nm and an 8 x 8 VCSEL array operated at 850 nm are used for HOE recording and reconstruction, respectively. The designed lens is experimentally demonstrated, and the experimental results of the lens almost agree with the numerical results.     

Techniques for phase correction in coherent ultrasound imaging systems

The problem of phase aberrations modeled as a near field thin phase screen is considered. Here three new techniques for phase aberration correction are presented. In the "central element" correction technique the echo-signal at each array element is aligned with the signal at the central array element. In the "variable speckle look-back" correction technique the signal at each array element is aligned with the sum of signals from all previously corrected elements. In the "variable central speckle look-back" correction technique the signal at each array element is aligned with the sum of signals from the central group of all previously corrected elements. The performance of new techniques for phase aberration correction is tested by means of simulating the point-spread function for both point and speckle targets. The results of simulation show that the new techniques have the better accuracy of phase correction than the classical "neighbor element" technique.     

Improvement of the axial trapping effect using azimuthally polarised trapping beam

A dual optical tweezers system,which consists of a doughnut mode optical tweezer (DMOT) with the azimuthally polarised trapping beam and a solid mode optical tweezer (SMOT) with the Gauss trapping beam was constructed to compare the axial trapping effect of DMOT and SMOT.The long-distance axial trapping of ST68 microbubbles (MBs) achieved by DMOT was more stable than that of SMOT.Moreover the axial trapping force measured using the viscous drag method,was depended on the diameter of the particle,the laser power,and the numerical aperture (NA) of the objective lens.The measurement of the axial trapping force and the acquisition of CCD images of trapping effect confirmed that the DMOT showed excellent axial trapping ability than SMOT.A simple and effective method is developed to improve axial trapping effect using the azimuthally polarized beam as trapping beam.This is helpful for the long-distance manipulating of particles especially polarised biological objects in axial direction.     

基于液晶空间光调制器的全息显示

在传统的纯相位全息显示系统中, 一般基于快速傅里叶变换(FFT)算法来计算相位全息图, 在FFT的计算中需要遵循Nyquist采样定理, 因此, 重建图像的尺寸往往受限于空间光调制器的固定采样率. 这个限制可以通过卷积算法或者两步菲涅耳衍射算法来解决, 但是需要使用多个FFT的计算, 导致计算量增大. 鉴于此, 提出了一种基于透镜的纯相位全息图计算方法. 在全息图的计算中, 通过透镜的成像原理建立一个采样率可变的虚拟全息面, 通过调节相应的距离参数使得在全息图的计算中可以任意调节原始图像的采样率, 摆脱了传统方法中液晶空间光调制器带宽积对重建图像尺寸的限制, 并且这种算法只需使用一次FFT就能达到变采样率的衍射计算, 大幅提高了全息图的计算速度. 数值模拟及光学实验结果证明了此方法可以在全息显示光学系统中清晰地重建不同尺寸的图像. 同时该系统可以有效地消除由空间光调制器的像素化结构带来的零级衍射.