利用联合付里叶变换谱干涉法测量透镜焦距

本文提出了采用联合付里叶变换频谱干涉法测量透镜焦距的方法。输入面上两个分布完全相同的图像经光学付里叶变换在频谱面上得到二者付里叶变换频谱的干涉条纹，通过测量干涉条纹的间距即可得到透镜的焦距。该方法装置简单、操作调整方便；易于采用实时空间光调制器、ＣＣＤ及微机实现快速自动测量，且具有较高的精度。文中进行了原理分析和实验验证。     

The use of a plane parallel glass plate for determining the lens' parameters

The present article reports a shearing interferometric technique for determining the various lens' parameters, namely, the focal length, refractive index, radii of curvatures etc. The wave aberrations have also been investigated for the different values of the focal length of the same lens by immersing it in various liquids. The lens itself acts both as autocollimator and decollimator. Modified criteria for evaluating the correct position of the focal length have been adopted. The defocusing involved is observed in terms of the interference fringes. The plane parallel glass plate acts as a double shearing interferometer. The location of the point source is confirmed by testing the wavefront parallelism. A graph (refractive index versus lens' power) with various liquids has been plotted which gives the desired parameters.     

Focus depth characteristics of lenses with long focal depth designed by a focal depth function

The validity of a focal length function is investigated in designing optical element with long focal depth and high lateral resolution. The designed lenses with different starting focal length are studied. Two focusing performance measures, focal depth and lateral resolution, are presented. Comparing with the conventional lens and optical element designed by other focal length function, numerical results of the designed optics element indicate that the long focal depth and high lateral resolution are achieved. The validity of the focal length function is confirmed. Meanwhile, the designed optical element is similar with the lens with spherical aberration. It means that one can easily implement long focal depth by applying appropriate phase modulation to a lens with spherical aberration.     

Focusing effect of a graded index photonic crystal lens

We present a new graded-index photonic crystal (GRIN PhC) structure which can be made by laser interference lithography (LIL). It can be applied as miniaturized focusing lens. Numerical simulations are carried out on the structures with different widths, lengths, and modulations. In the qualitative analysis of the focal length, focusing of a GRIN PhC was proved to originate from both the graded sizes of the rods and multimode interference. Multimode interference dominates the focusing effect when a GRIN PhC has a small length or a small difference in the rod sizes. Intensity distributions in different cases were given to support the conclusion.     

Focal length measurement of a varifocal liquid lens with capacitance detection

This paper reports on a detailed deformation model of varifocal liquid lenses fabricated by Parylene-on-liquid-deposition (POLD), which can be applied to measure and adjust the focal length of such lenses without using extra sensors or sensing mechanisms. The lens was fabricated by encapsulating a liquid between a transparent electrode and a polymer film that was covered with a metal electrode. When voltage is applied to the two electrodes, the lens deforms due to the electrostatic force, and its focal length and the capacitance between the two electrodes change simultaneously. This characteristic enables the focal length of the lens to be adjusted and detected by measuring the capacitance change. The focal length of the fabricated varifocal liquid lens changed from 153.6 to 82.6 mm by applying 150-V. The focal length change of the liquid lens was calculated from the change in its capacitance. Finally, to confirm the efficiency of this varifocal liquid lens, we fabricated a confocal distance sensor using the lens for laser scanning and demonstrated that this system can be used to measure distances of 94–140 mm with an average error of 0.83 mm and a standard deviation of 0.77 mm.     

计算全息法测量长焦透镜面形和焦距

为了同时对长焦透镜的面形和焦距进行高精度检测,提出在Zygo干涉仪的球面光路中加入一个二元衍射元件作为检测件的计算全息法。 首先对计算全息法检测长焦透镜的面形和焦距进行了理论推导,并给出焦距误差公式。在Zemax中使用在平面基底上制作的二元衍射元件对一个长焦透镜的面形和焦距进行了模拟检测,其中对该长焦透镜面形的干涉检测PV值为0.0034λ,对焦距的检测精度为-0.11%。最后详细分析了两类误差对检测结果的影响,其中光学元件的位置误差影响不超过0.1λ;二元衍射元件的制造误差影响约0.01λ,在具体制造过程中,其径向位置误差和台阶误差可分别在2 μm和5 nm之内。在综合考虑各项误差的情况下,该方法的检测精度仍然可控制在2λ/25之内。     

自参考激光剪切干涉法测量透镜焦距的实验研究

本文在改进的激光平板剪切干涉法基础上,提出了测量透镜焦距的一种新的实验方案。此方案根据透镜节点特性,以两组干涉条纹的平行作为判据,测量过程简便且精度较高。     

基于平行光管法的薄凸透镜焦距测量

薄凸透镜是光学仪器中最重要、最基本的元件,在天文、军事、医学等众多领域发挥着重要作用。焦距是薄透镜、反射镜等光学系统最重要的特性参量,因而准确测量薄透镜的焦距则显得尤为重要。实验室测量薄凸透镜焦距的方法有物距像距法、自准直法、光电法、平行光管法等。由于采用前3种方法测量透镜焦距的精度偏低,针对该问题,提出利用平行光管法测量薄凸透镜的焦距,并对实验误差作简单分析。实验结果表明,该方法可以高精度地测量薄凸透镜焦距,相对误差仅为0.138%。因此,采用平行光管法的薄凸透镜焦距测量方法是有效可行的。     

Studies of the characteristic parameters for a flattened-Gaussian beam through a defocusing lens

By introducing an equivalent focal length, analytical propagation equations of the characteristic parameters for a flattened-Gaussian beam through a defocusing lens in free space are obtained on the basis of Collins diffraction formula and definition of high-order intensity moments. The parametric characteristics of beam width, kurtosis parameter and power in the bucket are analyzed and discussed analytically or numerically. Numerical results show that the effects of different kinds or values of defocusing coefficient of the lens on these parameters are different. It is concluded that the action of the lens with different defocusing coefficient can be compensated by a series of lenses with different focal length in theory.     

大孔径变焦投影镜头设计

为了实现某一大孔径定焦投影镜头作为初始结构, 经过优化设计后成为大孔径变焦投影镜头, 根据设计目标的DMD对角线尺寸, 利用AUTOCAD对选择的定焦距系统的初始结构尺寸进行测绘, 初步选择各镜材料, 规划成5组元变焦系统, 利用各种操作数对镜头的基本参数和外形尺寸进行限制, 并合理利用2个非球面, 在光学设计软件Zemax与CODE V中往返优化, 得到一款在可见光波段内, 短焦距为14.61 mm、视场角为60°、F数为1.5, 长焦距为29.31 mm、视场角为30°、F数为1.6的变焦投影镜头。设计结果表明:各视场的传递函数(MTF)值在截至频率60 lp/mm处不低于0.46, 各焦距处的弥散角不超出1.6', 镜头具有良好的像质。该镜头系统由11块透镜和1块平行平板组成, 其中透镜2使用了非球面镜, 该镜头片数较少, 透镜折射率不高, 材料容易选择。     

The use of defocussed position of a Ronchi grating for evaluating the refractive index of lens

This report describes a Ronchi-grating shearing interferometric collimation method for determining the refractive index of a lens. A new formula has been deduced for the refractive index of the lens, which is independent of lens parameters. This newly developed device has two lenses. One of them collimates the light from a point source while the other acts as a decollimator. The point source acting as a test target is situated in the front focal plane of the collimator. The test lens is placed inside a glass cell in the back focal plane of the collimator. The Ronchi grating is exactly placed in the back focal plane of the decollimator, and a fringe-free space is observed in the common region. When the test lens is immersed in a liquid cell, it disturbs the focal point and hence interference fringes are observed. The combined system consisting of the test lens and the decollimator is moved to bring the focal point on the Ronchi grating. Thus, the difference between the two settings gives the amount of defocusing.     

Analysis of moiré fringes for measuring the focal length of lenses

We describe a technique based on fast Fourier transform and least-squares fit for automated analysis of moiré fringe patterns for accurately measuring the focal length of lenses. An interference fringe pattern is produced by a reflective diffraction grating interferometer and illuminates the test lens. Moiré fringes are generated by digitally superimposing the magnified fringe pattern imaged by the lens on the interference fringe pattern without the test lens. We analyze two common ways to generate the digital moiré effect: multiplication and subtraction with successive rectification of the two digitally stored intensity distributions, and we show that in the latter case by means of the described technique it is possible to determine the moiré spatial frequency by a simple and fully automated procedure.     

薄透镜厚度引起焦距测量误差的探究

从理想光具组的焦距公式出发,理论上分析了薄透镜厚度引起焦距测量的误差。采用物距像距法测定焦距,并与二次成像法测得的焦距比较,得出实验结论：采用物距像距法测量焦距,因薄透镜厚度引起的误差大小等于物距像距法测得的焦距与二次成像法测得的焦距之差;由于薄透镜的厚度越厚,折射越靠近光心,所测得的焦距值会偏小,因此对厚度引起的系统误差进行修正,得到修正后的焦距为fm＋Δf。     

2.94 μm Er:YAG激光热效应数值模拟及实验研究

理论分析了Er:YAG激光晶体的热退偏效应,模拟计算了该晶体棒端面退偏的分布,并进行了偏光干涉实验验证。结果表明,数值模拟和实验结果完全一致,热退偏效应随抽运能量增大而增强,退偏分布呈十字形,最大退偏发生在晶体棒端面上与起偏器偏振方向成45°方位处。同时,还阐明了一种利用临界稳定腔来测量灯抽运脉冲Er:YAG激光器有效热透镜焦距的简单方法,测量出不同抽运功率下Er:YAG晶体的等效热焦距。     

基于Talbot-Moiré法的长焦透镜焦距

 长焦距测量的Talbot Moiré法是研究热点,目前很多方法虽然都是基于Talbot现象和Moiré技术,但基本原理和实验方案各不相同,因此焦距计算公式也不相同。基于透镜位相变换作用,利用Talbot效应和Moiré条纹,通过图像处理的方法获得条纹的斜率变化,根据焦距与莫尔条纹斜率之间的关系求得透镜焦距。由于长焦透镜的焦距相对于被测透镜厚度大得多,完全可以看作是薄透镜对光束的变换,可用薄透镜对球面波的变换作用来近似表示其对高斯光束的变换。因此,该方法测量长焦透镜焦距对于高斯光束与非高斯光束焦距测量结果无差别,均适用。最后全面分析了该测量方法的误差及精度极限。在影响测量精度的各个误差因素中,光栅节距误差对焦距测量的影响最为显著。     

透镜初级球差的横向剪切干涉条纹研究

利用玻璃平行平板构成简单的横向剪切干涉仪可以观察到单薄透镜形成的准直光束的剪切干涉条纹,由干涉条纹分布求出对应的几何像差和离焦量.用焦距为190 mm的单薄透镜做实验,实验结果与计算机模拟结果符合,说明可以从剪切干涉条纹的分布求出透镜的轴向调整误差和初级球差.     

Thermal lens measurement technique in end-pumped solid state lasers: Application to diode-pumped microchip lasers

A simple derivation, which relates the thermal lens focal length in solid state lasers to pump power and a method for direct estimation of thermal lens focal length, is reported. This method is applicable to any type of stable resonator. The method is used for the measurement of the thermal lens focal length with an accuracy of 8% in an axially pumped microchip laser. The variation of focal length with pump power is also measured.     

一种新颖的简易凸透镜自动测焦设计方法

提出一种凸透镜自动测焦的设计方法。该方法直接从凸透镜焦距定义出发,应用凸透镜汇聚平行光于焦点测量其焦距,平行光采用激光器→扩束-准直镜获得。巧妙运用光敏电阻阵列设计解决调"共轴"问题,恰当设计测量过程轻松给出焦距测试结果。设计集光机电技术于一体,各部分技能又都很基础,具有广泛的实用性,整体设计方案可拓性也很强,具有较高的教学价值。     

反射法测凹透镜焦距

本文分析推导了透镜的凹面反射成像与凹透镜焦距的关系,介绍了利用此关系较方便地测量凹透镜焦距的方法。     

High-speed varifocal imaging with a tunable acoustic gradient index of refraction lens

Fluidic lenses allow for varifocal optical elements, but current approaches are limited by the speed at which focal length can be changed. Here we demonstrate the use of a tunable acoustic gradient (TAG) index of refraction lens as a fast varifocal element. The optical power of the TAG lens varies continuously, allowing for rapid selection and modification of the effective focal length at time scales of 1 mus and shorter. The wavefront curvature applied to the incident light is experimentally quantified as a function of time, and single-frame imaging is demonstrated. Results indicate that the TAG lens can successfully be employed to perform high-rate imaging at multiple locations.