Analysis of closed-boundary cylindrical microlenses with long focal depth designed by the general focal length function

In this paper, the general focal length function is used to design two-dimensional closed-boundary cylindrical microlenses (CBCMs) with long focal depth. The focusing characteristics of the designed microlenses is investigated by rigorous electromagnetic theory and the boundary element method. A number of focusing performance measures of the designed microlenses, such as the real focal depth, the focal depth range, the focal spot size, and the diffraction efficiency, are presented in detailed. As comparison, the focusing performance of the conventional lenses with the same parameters are investigated simultaneously. Our analysis indicates that the general focal length function is valid in designing CBCMs with larger extended focal depth. Comparing with the open-boundary cylindrical microlenses (OBCMs) designed using the same focal length function, we also find that the designed CBCMs with low f-number exhibit superiority of long focal depth.     

大孔径长焦距摄远物镜光学系统设计

对于长焦距摄远光学系统，大相对孔径意味着成像亮度更加优秀，但是也伴随着孔径边缘像差变差而难以校正的难题。利用折反系统减小光学系统总长，采用反射结构为基础，搭配前后两组校正镜构成光学系统，设计出大相对孔径，总长较短的摄远光学系统。光学系统工作波段为可见光波段，焦距1 000 mm，F数2.1，摄远比0.52，光学总长远小于焦距，遮拦比45%，全视场MTF在空间频率80 lp/mm处大于0.3，像面直径11 mm。该光学系统镜片全部采用球面镜，光学系统由2片反射镜和7片透射镜组成，结构紧凑，成像质量好。对摄远物镜进行公差分析，得出该设计公差较宽松。     

基于卡塞格林系统的红外制冷型长焦分档变倍光学系统的设计

本文基于卡塞格林系统设计了红外制冷型长焦分档变倍光学系统,计算、推导了光学初始参数及组元的光焦度分配。采用了二次成像结构形式,主物镜组采用R-C光学结构用于缩短筒长,使用投影镜组解决冷屏匹配问题,利用调焦镜实现调焦,通过切换投影镜组后组实现变倍,然后对光学系统像差进行了优化设计,分别给出了长焦系统和短焦系统不同视场的成像质量优化结果,0.8视场内光学传递函数在空间频率17 lp/mm时均大于0.4。最后对主要结构进行了相应的精度分析,结果表明该设计能够很好地满足工程实际需要。     

Rigorous electromagnetic analysis of metallic cylindrical focusing micromirrors with high diffraction efficiency, achromatic aberration and long focal depth

In this paper, we propose a kind of metallic cylindrical focusing micromirrors (MCFMs) with parabolic profiles, and the focal performance is investigated based on rigorous electromagnetic theory and the boundary element method (BEM). Numerical results by the BEM show that the proposed MCFM possesses a high diffraction efficiency and axially achromatic aberration. In addition, through designing a modulating phase function, the MCFM holds long focal depth and high transverse resolution simultaneously. It is believed that the MCFM should have wide application prospects in micro-optical systems, such as micro solar concentrators.     

High-resolution optical coherence tomography over a large depth range with an axicon lens

In optical coherence tomography, axial and lateral resolutions are determined by the source coherence length and the numerical aperture of the sampling lens, respectively. Whereas axial resolution can be improved by use of a broadband light source, there is a trade-off between lateral resolution and focusing depth when conventional optical elements are used. We report on the incorporation of an axicon lens into the sample arm of an interferometer to overcome this limitation. Using an axicon lens with a top angle of 160 degrees , we maintained 10-microm or better lateral resolution over a focusing depth of at least 6 mm. In addition to having high lateral resolution, the focusing spot has an intensity that is approximately constant over a greater depth range than when a conventional lens is used.     

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。     

基于大面阵CCD的复消色差航空相机物镜设计

为了满足航空相机物镜结构简单及高分辨率的要求,提出了一种基于波差法校正长焦距、宽波段的大面阵CCD航空相机物镜二级光谱的方法.介绍了二级光谱的基本原理,给出了波差法设计复消色差物镜的方程组.采用普通光学材料设计了复消色差航空相机物镜,系统焦距为400 mm,相对孔径为F/4,工作波段为420～850 nm.给出了光学系统图、纵向像差图及调制传递函数图.设计结果表明,采用该方法设计的航空相机物镜在60 lp/mm处各视场传递函数均在0.75以上,满足接收器件有效尺寸为36 mm×48 mm的大面阵CCD成像要求.     

Extending the depth of focus with high NA lens axicon

Based on vectorial Debye theory, tight focusing of x-polarized beam with high NA lens axicon is studied. The high NA lens axicon utilizes spherical aberration to duplicate the performance of an axicon and to create an extended focal line. The intensity distribution in the focal region is illustrated by numerical calculations. We show that the high NA lens axicon system can generates a sub wavelength beam (0.826λ) with depth of focus around 10λ.     

三环位相型光瞳滤波器的横向超分辨与轴向焦深扩展

用矢量衍射方法分析了线偏振光入射到带有三环位相型光瞳滤波器的高数值孔径物镜时,焦点的轴向和横向光强分布.数值模拟结果表明,高数值孔径物镜聚焦时需同时考虑光强的轴向和横向分布.通过加入三环位相光瞳滤波器,在实现横向超分辨的同时实现了光学系统轴向焦深扩展和轴向光强分布平坦化,并且位相调制深度变化时,会出现轴向焦移现象.对三环位相光瞳滤波器结构进行了优化,得出了优化结果. 关键词： 光学超分辨 扩展焦深 位相型光瞳滤波器 矢量衍射方法     

太阳光光纤耦合光学系统设计

介绍一种长焦距、大口径太阳光光纤耦合系统的光学设计。为达到减小大口径单透镜汇聚太阳光所产生的球差和色差的目的,采用聚光透镜后增加消像差光学系统的方法,并用Zemax软件设计优化出适用于光纤耦合的光学系统,经过优化设计得到光斑半径为45.043 m,能量集中度达95 %以上,像方孔径角为9.090 2,系统总长525.584 mm,满足数值孔径为0.22,芯径直径为1.5 mm的石英光纤的耦合要求。     

Hybrid lens with corrected sphero-chromatic aberration

An optical imaging element is considered, which consists of a plano-convex spherical glass lens and a holographic lens recorded on the flat surface. Such a ‘hybrid lens’ enables one simultaneously to correct spherical aberration and longitudinal chromatism for two given wavelengths. The imaging quality of such an achromatic lens of focal length f = 100 mm and relative aperture 1:10 is evaluated by the ray tracing method. The results ensure that the performance of such a hybrid lens is acceptable for field angles as high as 5:100.     

测量接触镜近轴后顶焦距可行性分析

主要论述了由焦度仪测量的接触镜实际后顶焦距转化为近轴后顶焦距的可行性问题以及近轴后顶焦距与实际应用相适应性的问题。通过分析和比对一些厂家生产的接触镜光学结构参量 r,n,d后认为 ,由于接触镜球差较大 ,而球差由光学结构参量确定 ,因而同一近轴后顶焦距不同 ,光学结构参量的接触镜实测后顶焦距也不同 ,并且偏差超出了允许范围。所以实际后顶焦距转化为近轴后顶焦距是不恰当的。同时近轴后顶焦距的倒数表征的光焦度与临床验光给出的实际光焦度意义不同 ,因而定义与实际应用不相适应。作者最后提出了接触镜后顶光焦度定义的修正建议     

大口径超长焦距紧凑型光学系统设计

为满足空间遥感光学系统结构紧凑、体积小以及高分辨率的需求,提出了一种长焦距紧凑型光学系统的设计方法。基于高斯光学和初级像差理论,创建了同轴四反射镜系统的初始结构,通过视场偏置的方法避免二次遮拦。对设计的大口径超长焦距同轴偏视场四反射光学系统进行优化,系统口径1 800 mm,有效焦距25 000 mm,全视场角1°×0.1°。设计结果表明,系统设计波像差优于λ/50(λ=632.8 nm),全视场相对畸变小于0.4%,光学筒长仅为有效焦距的1/10,结构简单紧凑,像质接近衍射极限,对大口径超长焦距空间遥感光学系统的设计具有一定的借鉴作用。     

基于三组元可调光焦度器件的变焦光学系统设计

采用矩阵光学理论分析三组元可调光焦度器件的变焦系统的一阶属性，得到了基于系统放大率的光焦度控制方程。结合三组元系统初始参数并以系统球差最小为目标，对其进行了初始结构设计，得到了透镜形状参数的控制函数，然后进行光焦度和像质评价验证计算，最后对设计实例进行了归化对比验证。验证结果表明:对球差最小优化值的求解可信，设计方法为采用可调光焦度器件设计变焦系统提供了参考。     

红外双焦无热化空间相机光学镜头设计

针对空间碎片探测相机光学镜头的设计要求,提出了一种全新的紧凑型、小型化、轻量化、高像质、可全天候工作、使用环境恶劣的光学镜头,突破了以往该类系统结构复杂、体积大、重量重、仅有一个焦距的瓶颈。利用衍射光学元件特殊的特性进行消色差和消热差设计,并利用锗和硅混合来校正系统色球差,最终设计镜头的焦距为30, 120 mm,相对孔径为1/4。设计结果表明,在空间频率16 lp/mm处,－40～60 ℃温度范围内,短焦距、长焦距的传递函数值分别优于0.45和0.55,接近衍射极限;短焦距、长焦距的最大RMS弥散斑直径分别为15.8, 7.2 m,远小于探测器像元尺寸30 m,表明该系统在实际使用温度环境下具有良好的成像质量。     

紫外宽光谱大相对孔径光学系统设计

现有大部分紫外光学镜头的工作带宽较窄,紫外镜头的材料相对较少,镜头的紫外色差校正困难,导致其应用适应性降低。采用负正透镜交叠分布与类双高斯对称式结构形式,并利用熔石英材料和氟化钙材料本身的宽光谱透过性,设计了一种兼具大相对孔径、宽视场和高分辨率的紫外宽光谱光学系统。该系统的工作波长范围为240 nm～360 nm,紫外工作带宽高达120 nm,所有透镜均采用球面透镜,便于加工和检测。在全视场范围内,以中心波长300 nm为参考波长,系统横向色差最大值不超过1个像素,在截止频率50 lp·mm?1处的调制传递函数值优于0.4,并且各个视场的像点弥散斑半径均方根值均优于10 μm。设计结果表明:该紫外宽光谱光学系统的成像性能优良,分辨率高,色差小,满足设计要求。     

宽光谱长焦距物镜的复消色差设计

介绍了以摄远型为初始结构的宽光谱长焦距折射式物镜的设计方法。对玻璃材料的选择进行了分析,并建立了能够分配三分离透镜组光焦度的复消色差方程组。通过理论计算和ZEMAX光学设计软件的优化,给出工作波长范围在0.4~0.9μm、焦距为400 mm、视场角为6.2°、相对孔径为1∶4的设计实例。设计结果表明,二级光谱得到了很好的校正,像质优良。     

Influences of pump beam distribution on thermal lensing spherical aberration in an LD end-pumped Nd:YAG laser

A numerical investigation is made on the thermal lensing and spherical aberration effect in an LD end-pumped Nd:YAG laser. Based on the finite element method (FEM), the laser rod temperature distribution is calculated and the focal length of the thermal lens is deduced, the influences of pump beam on the thermal lensing spherical aberration are mainly studied. The results show the thermal lens which focal length varied with the radial coordinate r is not an ideal lens. Given the heat dissipation boundary conditions, the radial dependent focal length will be shortened when the pump power raised or the waist radius of the pump beam reduced, meanwhile the radial differences of the focal length will decrease when the pump power increased. For a Super-Gaussian profile pump beam, the higher the exponent number, the more similar to flat top the pump beam is, and the less the radial differences of the focal length are.     

Design and properties of binary axilens

A novel optical element, axilens, proposed by Davidson et al., for achieving extended focal length is introduced. We propose a method to design the binary axilens which has high diffraction efficiency. Using computer numerical simulation, we designed 4 axilenses each has different parameters. In this paper we present our results and make comparison with that in ref. [1]. The properties of binary axilens such as the focal depth, the lateral resolution and the intensity distribution along axis is discussed.     

激光测头用二元准直透镜的研究

通过分析现用激光测头光学系统中所存在的制约测量范围与测量精度的问题，本文提出用二元长焦深、高分辨率器件取代传统准直透镜以提高测头技术性能，并详细推导了此二元器件的设计方法，给出了相位函数表达式。通过对一个设计实例的轴上光斑变化和光能分布情况的模拟计算，并与传统透镜相比较，说明这种二元器件用作准直透镜能够提高激光测头的技术性能。表明二元光学器件用于不接触测量系统具有巨大优势。