水下同步扫描三角测距成像理论建模及仿真分析

针对激光同步扫描三角测距成像系统水下应用时,考虑不同介质界面的折射效应,通过理论建模,得出水下同步扫描三角测距成像系统的空间三维坐标测量关系表达式。分析了基线距离、接收透镜焦距等系统主要参数对距离测量分辨率的影响,以及成像探测器长度对测量范围的影响。仿真结果表明:增大基线距离和接收透镜焦距,有利于提高距离测量分辨率,增加成像探测器长度,有利于增大系统测量范围,为水下同步扫描三角测距成像系统的设计提供了理论依据。     

Spectral focusing characteristics of a grazing-incidence flat-field grating spectrometer

The spectral focusing characteristics of a grazing-incidence flat-field spectrometer with a spherical variable-line-spacing grating in the 5－40nm spectral range are presented. The spectrometer can be used for any object at a distance in the 50mm－infinity range from the grating apex with a diffracted spectrum sharply focused on an almost flat focal plane at a constant distance from the grating apex.     

Performance of an optical stand-off control system for laser materials processing

This paper presents an experimental investigation into a high-bandwidth optical range sensor for laser materials processing stand-off control. Radiation from a low-power laser beam is focused onto a workpiece surface and light reflected from the surface is collected through a main lens and directed into an imaging lens which focuses the signal to two positions after being split by a beam splitter. The irradiances of the two beams are detected by photodiodes placed behind pinhole apertures positioned fore and aft of the two focal positions. A differential amplifier is used to generate an output signal that determines the magnitude and direction of any workpiece displacement. The system facilitates a measuring range of ±6 mm. A set of of experiments are performed and results are analysed for different setup configurations. The approximate range of instrument linearity is ±1 mm for the 75-mm focal length main less and ±2 mm for the 120-mm lens; in this linear range the optimal accuracy resolution is 1 μm. The system's effectiveness is controlling the stand-off distance of a laser cutting machine, and hence cut quality, is assessed.     

A conical air-coupled capacitance transducer for surface imaging

This paper describes the construction and operation of an air-coupled capacitance transducer with a conical backplate. This was designed to produce a focal region over an extended distance along the transducer axis. Measurements were performed to examine both the frequency response of the transducer in pulse-echo mode, and the lateral resolution for imaging purposes. The radiated field was measured and compared to theory, and the extent of the focal region determined. Images of surface topography are presented, to illustrate the range of application of the transducer.     

High-reflectivity high-contrast grating focusing reflector on silicon-on-insulator wafer

A high-contrast grating(HCG) focusing reflector providing phase front control of reflected light and high reflectivity is proposed and fabricated.Basic design rules to engineer this category of structures are given in detail.A 1550 nm TM polarized incident light of 11.86 mm in focal length and 0.8320 in reflectivity is obtained in experiment.The wavelength dependence of the fabricated HCGs from 1530 nm to 1580 nm is also tested.The test results show that the focal length is in the range of 11.81-12 mm,which is close to the designed focal length of 15 mm.The reflectivity is almost above 0.56 within a bandwidth of 50 nm.At a distance of 11.86 mm,the light is focused to a round spot with the highest concentration,which is much smaller than the size of the incident beam.The FWHM of the reflected light beam decreases to 120 nm,and the intensity increases to 1.18.     

Diffraction of a modulated laser beam in 3ω optics system

Based on diffraction optical theory, diffraction of a laser beam with periodic amplitude modulation and phase distortion is derived in 3ω optics system. Influence of defocus distance and focal length of a focusing lens on intensity distribution of diffraction light is investigated by numerical simulation. The results show that appropriate distance away from the focus spot and increase the focal length in final optical systems are beneficial to control the modulation of light intensity fluctuations and reduce the optical components damage caused by small-scale self-focusing effect.     

透射晶体谱仪及其理论计算

为了测量更广能量范围的等离子体辐射的硬X射线轫致辐射光谱,以获得激光等离子体超热电子能谱的特性,基于柱面弯曲晶体的分光原理,提出了透射晶体谱仪。为满足实验中光源到谱仪距离不同的需要,设计了Johann型可调节透射晶体谱仪。谱仪中的会聚狭缝设计成可移动的,位置随着光源到谱仪距离的变化而改变。通过理论计算获得了会聚狭缝位置变量与光源距离变化之间的关系,得出小角度(小于0.2 rad)入射时能够保证入射光线经过晶体后近似会聚于一点,并对谱仪具体设计时遇到的一些问题,给出了初步的理论分析和看法。该谱仪中会聚狭缝的可调节解除了谱仪到光源距离固定的限制;前端晶体的可更换,也增加了谱仪测量的灵活性。     

极小景深条件下显微镜大范围聚焦算法

自动聚焦是全自动显微成像中的一项关键技术。为了克服已有聚焦算法对聚焦起始点敏感及聚焦范围过小的问题,从分析大范围聚焦曲线形态入手,依据离焦距离、初始搜索方向和初始搜索范围等参量和曲线形态参数间的制约关系,将聚焦划分为六种类型,极值搜索中结合聚焦函数值的变化信息并通过启发式方式将未知类型转化为基本型,从而实现了大范围聚焦到小范围聚焦的转换。然后在聚焦曲线陡峭区范围内对曲线进行高斯拟合以获取最优焦平面。基于自行研发的全自动显微镜系统对提出的算法进行了验证,实验结果证明了该算法的有效性。     

硬X射线透射晶体谱仪的设计性能参数

激光等离子体相互作用高分辨硬X射线光谱的测量通常采用柱面透射弯晶谱仪实现。利用几何光学模型对柱面透射弯晶谱仪的关键技术参数进行了理论计算和数值模拟,给出了谱仪弯晶曲率半径、光源到晶体的距离、光源尺寸和探测器的位置等因素对谱仪测谱范围和分辨能力的影响情况,分析了光谱分辨水平随能点的变化。分析结果表明:晶体曲率半径对测谱范围和谱分辨能力影响大,在光源尺寸较小时,随着探测器与罗兰圆距离的增加,谱线之间距离增加的速度大于光谱线宽增加的速度,使得分辨能力增加。     

摄影焦距对测量箭体漂移影响的分析

高速摄影仪在航天试验靶场中主要用于火箭垂直起飞段的横向漂移测量,它采用近距离、短焦距物镜对火箭进行跟踪测量,任何微小的线量误差将带来较大的测量误差,以致严重影响火箭漂移量的处理精度。为此,建立了高速摄影仪摄影焦距的微量变化对箭体漂移量误差产生影响的数学模型,利用标称数据进行仿真分析,并给出焦距修正系数的计算方法。     

Research on OEF geometry control algorithm in dual-galvanometric laser scanning manufacturing

For the dual-galvanometric laser scanning manufacturing, the traditional geometry algorithm-fθ only considered the distance between the two swaying mirrors, the distance between the swaying mirror and the convex lens, the mirror swaying angle, and the lens focal length. And it could not correctly express the manufacturing track which was made geometry distorted. Based on analysis, a creative geometry control algorithm - optical entire factors (OEF) was brought forward. From the creative algorithm it can be known that OEF geometry control algorithm was concerned with not only the distance of the two swaying mirrors, distance between the swaying mirror and the convex lens, mirror swaying angle, and lens focal length, but also the lens central height, lens convex radius, and medium refractive index. The manufacturing system can manufacture satisfied geometry with the creative double ends approach (DEA) control model based on OEF in the experiments.     

Laser-induced ignition by optical breakdown

This paper is an experimental work of the applied methodical character in which as an attempt to optimize a laser ignition system a systematic study of the best incoupling geometry for the employed Nd:YAG laser was performed. The incoupling geometry comprises the pump fiber and an aspheric collimating lens. In this context, the distance between pump fiber and collimating lens was made continuously variable. The distance between fiber and lens primarily influences the diameter of the pump beam. In this way, it is possible to control the pulse energy as well as the number of pulses generated within a pump cycle. Furthermore, investigations to analyze the focal size dependence of plasma generation were carried out. As a result, it was found that it is possible to reduce optical losses caused by plasma transmission by choosing an optimum focal volume. This experiment was carried out for different pressures and focal volumes.     

基于相位展开及拼接算法的一种高精度大量程宽光谱干涉显微术

宽光谱干涉显微术广泛应用于高精密检测领域,它测量样品形貌通常采用垂直扫描干涉术对亚微米至毫米级特征进行测量,以及相移干涉术对纳米级特征进行测量。其中,相移干涉术精度可达纳米级,但量程有限,高度变化对应的相位需限制在区间内。采用包裹相位展开算法可以扩展相移干涉术的量程,也仅适用于平滑表面,当高度起伏超出焦深或者光源相干长度的限定范围时,干涉条纹模糊或对比度丧失,所解算的结果将产生较大误差甚至错误。提出一种基于相位展开及拼接算法的高精度、大量程宽光谱干涉显微测量方法,以干涉条纹调制度量化条纹质量,条纹对比度高、成像清晰的区域对应调制度较高,定义当前焦面条纹调制度高于阈值的区域为理想区域,定义焦面条纹调制度低于阈值的区域为问题区域。以相位展开算法获得理想区域中的样品相位分布,问题区域的包裹相位不进行展开。使用微位移结构纵向移动物镜焦平面,选择合理的步长,使相邻焦面位置理想区域展开后的真实相位保持部分区域重合,根据重合区域的相位值均差可以实现不同焦面位置的高精度相位拼接,最终获得扩展量程的高精度真实相位结果,进而可以恢复样品完整的表面形貌分布。该算法通过对理想区域的筛选,避免了相位在问题区域展...     

红外光学系统焦距测量装置校准规范说明

红外光学系统焦距测量装置是红外光学系统焦距校准和检测的技术手段之一。红外光学系统焦距测量装置校准规范不仅应用于计量部门，保证计量部门日常校准工作的准确性、一致性和可溯源性，同时为红外光学系统焦距测量装置生产部门提供了技术依据，满足红外光学系统焦距测量装置用户在申请各种认证过程中对红外光学系统焦距测量系统的要求。简要介绍红外光学系统焦距测量装置校准规范的主要构成和主要参数校准方法及不确定度评定。     

聚丙烯酸酯泡沫密度均匀性的射线检测技术

低密度泡沫材料大多存在一定程度的密度不均匀性，这对其后续使用性能将带来不良影响。文中简述了ICF靶用聚丙烯酸酯泡沫的制备方法，并利用β射线和X射线检测技术，对直径为mm量级的低密度聚丙烯酸酯泡沫柱进行密度分布表征。研究结果表明:泡沫柱沿轴向的密度分布比较均匀，而沿径向呈内低外高分布，形成了明显的密度梯度。实验表明:射线检测技术测量靶用低密度泡沫的方法可基本满足目前的实验要求，但密度分辨率和空间分辨率还有待进一步提高。     

Effects of excimer laser illumination on microdrilling into an oblique polymer surface

In this work, we present the experimental results of micromachining into polymethy-methacrylate exposed to oblique KrF excimer laser beams. The results of low-aspect-ratio ablations show that the ablation rate decreases monotonously with the increase of incident angle for various fluences. The ablation rate of high-aspect-ratio drilling with opening center on the focal plane is almost independent of incident angles and is less than that of low-aspect-ratio ablation. The results of high-aspect-ratio ablations show that the openings of the holes at a distance from the focal plane are enlarged and their edges are blurred. Besides, the depth of a hole in the samples oblique to the laser beam at a distance from the focal plane decreases with the increase of the distance from the focal plane. The number of deep holes generated by oblique laser beams through a matrix of apertures decreases with the increase of incident angle. Those phenomena reveal the influence of the local light intensity on microdrilling into an oblique surface.     

大气湍流中部分相干聚焦涡旋光束的传输特性

基于广义惠更斯-菲涅耳原理和相位结构函数的平方近似,研究了部分相干高斯-谢尔模型涡旋光束被聚焦后在大气湍流中的传输特性,得到了焦平面上光强解析表达式.利用该表达式,详细研究了该类光束在大气湍流中传输焦平面上的光强分布特性.结果表明：在大气湍流中,随着传输距离的增加,涡旋光束的奇异性逐渐降低.对于拓扑荷大的以及空间相干长度较长的涡旋光束,光束奇异性的保持相对要好.在一定的焦距长度和湍流大气条件下,我们可以通过调整光源的拓扑荷和相干长度控制焦面光强分布和焦斑大小.另外,有一定拓扑荷的涡旋光束可以在一定程度上降低大气湍流对传输光束焦面光强分布的影响.     

平焦场光栅光谱仪的新用法

计算发现,当平焦场光栅光谱仪的光源位置任意变化时,总能通过改变光栅的入射角,保持光谱焦平面到光栅的距离基本不变。以此为依据提出了平焦场光栅光谱仪的新用法,使得该谱仪使用灵活,适应性强,在极步外和软Ｘ射线光谱学的有关实验中发挥更大的作用。谱仪的摄谱范围５～４０ｎｍ之间。     

Optimization of Axial Intensity Point Spread Function

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Optimization of Axial Intensity Point Spread Function

It is known that for the converged laser beam, the axial intensity distribution corresponds to a Gaussian curve, that is, the intensity on the focal plane is the peak intensity. When it defocuses, the intensity would decrease rapidly. In optical data storage, for instance, we expect the intensity within a certain distance to be almost equal. In this paper, we propose to use a pure phase superresolution apodizer to optimize the axial intensity distribution of the converged laser beam and at the same time improve the resolution. The intensity point spread function remains almost identical in a wide range within the focal depth.