模式搜索法在光纤有源自动对准中的应用

提出基于模式搜索法的光纤有源自动对准算法,实现了多自由度同时寻优,解决了不同自由度之间的交叉耦合问题,提高了对准速度和对准精度。通过仿真与实验研究,与传统的爬山法进行对比。仿真结果表明,激光二极管与单模光纤五自由度对准时,模式搜索法只需20次迭代就可以找到最大点,收敛速度是爬山法的9倍。实验结果证明,横向调整两个自由度对准时,模式搜索法搜索速度比爬山法平均快10 s,定位成功率达到90%。     

Optical Fiber Catheter with Distal End Bending Mechanism Control for Raman Biospectroscopy

Abstract

This work proposes the development of an optical catheter with bending control of the distal end. The probe consists of seven optical fibers wrapped in a resin and a biocompatible flexible teflon tube with a novel mechanical device that allows bending of the distal extremity to access a desired location of a human organ. A central fiber is used for tissue Raman excitation, five fibers are used for Raman signal collection, and the seventh for “optoclinical” treatment applications. Infrared, dispersive Raman spectra at 785 nm excitation were employed to optically characterize the proposed catheter. An excitation transmission loss of 16% was found compared to the traditional six collecting fibers catheter, both with their distal tip straight. By bending of the distal tip at different angles, with turning the intermediated section of the catheter around cylinders of different diameters (one finds a correlation between curvature angle of the tip and cylinder diameter), the transmission loss coefficient and transmission were determined for each distal tip angle. A transmission reduction of 5% was found for a 180° curvature. This optical catheter could be very useful in clinics, providing a way to control the fiber tip position and angle onto the tissue or organ.     

球透镜耦合效率研究

根据能量积分法计算了球透镜用于激光二极管(LD)与单模光纤(SMF)之间耦合的耦合效率,并对其进行研究。结果表明:当采用单球透镜时,所带来的轴向偏差为±30 μm,横向偏差为±1.0 μm,沿着X-Y平面的轴向倾角偏差为±1.2°;当采用双球透镜时,角向偏差最大,横向偏差次之,轴向偏差最小。     

由正交傅里叶-梅林矩定位的双光纤耦合微内尺度测量

为了解决微内尺度的精密测量问题,提出了一种基于正交傅里叶-梅林矩(OFMM’s)定位的双光纤耦合瞄准触发式微内尺度测量方法。该方法通过耦合器实现光能量在不同光纤间的反向传输,把双光纤传感器测头的横向位移量转化为光束的偏转量,通过显微成像系统把此偏转量转化为CCD图像捕捉系统更大的横向位移量。为提高测量精度,运用OFMM’s的幅值旋转不变性和独特的图像形状细节特征的描述能力对CCD图像捕捉系统的图像信号进行亚像素定位;根据OFMM’s的实际位置进行补偿以提高输出图像边缘的定位精度,从而提高测量精度。对OFMM’s的定位精度及传感器性能进行了实验验证,并依据JJF(黑)8-2008,利用自行研制的微小孔径测量机实现了对直径为200μm、深2 000μm深盲孔的直径测量,其测量重复性不确定度优于0.25μm。     

水导激光微细加工中激光与水束光纤耦合技术

为了保证水导激光微细加工中会聚激光与水束光纤的耦合效果,建立了高精度的耦合对准系统,提出了新的耦合对准方法,研制了特殊结构的耦合装置。由于激光要经过空气层、玻璃层、水层进入水束光纤,因此根据计算结果,采用特殊方法来确定会聚透镜与水束光纤起始端(喷嘴孔)的距离;研究了激光在水束光纤中发生全反射的最大入射角;通过流体动力学仿真,设计了腔内流场分布均匀的耦合装置,保证了直径0.12mm的水束光纤的高耦合品质;研究了激光能量在水束光纤中的衰减,采用特定波长、脉冲能量的激光和特殊过滤的去离子水来减小激光能量在水束光纤中耦合的损耗率。试验结果表明,能生成导光长度超过100mm的水束光纤;采用该耦合技术能够在0.2mm厚的硅基晶片上以2mm/s速度切割出缝宽0.12mm的均匀窄缝,几乎无裂纹、无热影响区。该耦合技术能够很好满足水导激光微细加工的要求。     

Lensed plastic optical fiber with an aspherical fiber end formed by joining an aspherical plastic lens and a plastic optical fiber using laser transmission welding

In optical communication systems which require the coupling of the light source to the fiber, efficient coupling can be practically realized either using a separate lens or by direct formation of the lens at the fiber end. A novel lensed plastic optical fiber (LPOF) is presented with efficient coupling of the plastic optical fibers with a light source. An aspherical plastic lens was bound with a flattened plastic fiber end by laser transmission welding (LTW) to form an aspherical fiber endface which can provide better coupling efficiency than a spherical fiberface. An analysis demonstrates that LTW can offer strong welding with small heat affected zones that are appropriate for commercial use. In this study a useful method for manufacturing lensed-end fibers is developed and demonstrated experimentally.     

Remote Detection of Organochlorides With a Fiber Optic Based Sensor II. a Dedicated Portable Fluorimeter

ABSTRACT

A dedicated portable fluorimeter, for use with fiber optic chemical sensors (FOCS) has been designed, constructed, tested, and calibrated. This represents a major advance in the development of a FOCS system suitable for in-field use. The portable fluorimeter uses an incandescent lamp, instead of a laser, for FOCS excitation and a photodiode, in place of a photomultiplier tube for detecting the fluorescence signal. It uses an optical system which is internally connected to a unitized optical block by 600 μm core optical fibers, to minimize alignment problems and increase overall system ruggedness. The system noise is less than .1.5 mV and the long-term drift is less than ±2 mV/hour. Measurements of organochloride were made at concentrations as low as 80 parts-per-billion with a signal to noise ratio of 40:1.     

高温下小区域变形长时测量方法的研究及其应用

对于高温下服役的构件，焊缝区域较为狭小，焊缝以及热影响区（HAZ）的高温变形难以用传统的方法测量。文中利用石英光纤和数字图象处理技术，研究开发一种能在高温下长时测量局部变形的新方法和测量系统，分析讨论了测量精度，并用HK40炉管焊缝长时蠕变变形的测量，分析比较了焊缝和母材的蠕变性能差异。     

808nm高亮度半导体激光器光纤耦合器件

针对单个808nm单管半导体激光器输出功率低,采用端面泵浦方式对光纤激光器进行泵浦时受到限制的问题,本文利用空间合束技术制成高亮度半导体激光器光纤耦合模块来提高808nm单管半导体激光器泵浦掺Nd3+双包层光纤激光器的效率。首先,通过微透镜对每个单管半导体激光器进行快慢轴准直;然后,使用反射棱镜对每个激光器发出的光进行空间合束;最后,利用自行设计的扩束系统将合束后的光束进行扩束,聚焦进入光纤,从而极大地提高光纤耦合模块的亮度。实验中将4只连续输出功率为5W的单管半导体激光器发出的光束耦合进芯径为105μm、数值孔径(NA)为0.2的光纤,当工作电流为5.8A时,通过光纤输出的功率为15.22W,耦合效率达到74%,亮度超过1.4MW/cm2.sr。     

精密视觉印刷设备的自标定

为了提高全自动视觉印刷设备的精度,提出了一种简易、有效标定基于三自由度平面并联调整台的视觉丝网印刷设备的算法。首先,分析和标定了视觉测量系统,并通过激光干涉仪验证了结果的准确性。然后,分析了三自由度平面并联调整台的几何参数误差;基于印刷设备自身的视觉测量系统,分步标定了并联平台的动平台坐标系、传动比误差和仅需的部分几何误差源。提出了一种满足全姿态且适应不同制程的三角形面姿态插值方法和纠偏调整算法,从而避免了较为复杂的几何全参数辨识,降低了对调试人员的技术要求。实验结果表明：在并联调整台工作空间内,标定后的最大位置误差从标定前的161.6 μm下降为12.3 μm,最大姿态误差从标定前的2.232″下降为0.720″,基本满足印刷设备对精度的要求。     

A Novel Opto-Mechanical System Coupled to a Spectrophotometer for Measuring Coatings on Small Size Substrates and Optical Fiber Filters

Abstract

A novel opto-mechanical system coupled to a commercial spectrophotometer using optical fibers was developed to measure optical transmittance of small samples, like filters deposited on optical fiber tips or micrometric substrates, as well as to investigate transmission uniformity of filters by surface scanning. It consists of two identical modules, reference and sample, both inserted in the chamber of the spectrophotometer. Each module was formed by an optical fiber, 200 µm core diameter and numerical aperture of 0.22, supported by adjustable positioning mounts for easing alignment. The system was validated by measuring the transmittance spectrum of a coated glass substrate with and without the opto-mechanical system, showing no significant differences between both methods. To determine the system versatility were undergone two transmittance experiments: one for a filter deposited on the tip of an optical fiber and the other by scanning the surface of a coated glass substrate. It can be concluded that the opto-mechanical system allows to measurement the transmittance of small size filters and optical fibers filters, as well as to scan over large coated surfaces to investigate coating uniformity.     

Optimization of processing parameters for double-ridged rectangular tube rotary draw bending based on grey relational analysis

The rotary draw bending of double-ridged rectangular tube is a complex nonlinear physical process with multifactors coupling effects. Processing parameters, especially clearances and friction coefficients between tube and various dies, have a significant effect on the forming quality of the double-ridged rectangular tube in rotary draw bending. If the values of these processing parameters are inappropriate, some defects including cross-sectional deformation, wall thinning, and wall thickening easily occur in the bending process of double-ridged rectangular tube. So optimization of these processing parameters is of great importance to control these defects. Based on the grey relational analysis method combined with the orthogonal experimental design and finite element simulation, a grey relational analysis model was established for the rotary draw bending process of double-ridged rectangular H96 brass tube. With the model, optimization of clearances and friction coefficients between tube and various dies was implemented with consideration of interactive effects of the above defects. The results show that (1) the main factors influencing cross-sectional deformation, wall thickening, and wall thinning are tube–mandrel clearance Δc _m, tube-bending die clearance Δc _b, and tube–mandrel clearance Δc _m, respectively. (2) The optimal values of clearances Δc _m, Δc _p, Δc _w, and Δc _b and friction coefficients μ_m, μ_p, μ_w, and μ_b of tube–mandrel, tube–pressure die, tube–wiper die, and tube-bending die are 0.15, 0.2, 0.2, 0.2, 0.02, 0.3, 0.06 and 0.17 mm, respectively. Furthermore, the verification for the optimal values of these processing parameters was carried out, and the double-ridged rectangular H96 bent tube obtained by using the optimal values of these processing parameters has the minimum values of cross-sectional deformation, wall thinning, and wall thickening and can satisfy the national aviation industry standards.     

利用光压差分技术筛选细胞的影响参数

本文采用有限体积法建立了交叉型细胞分离模型,提出了一种基于光压差分的细胞筛选仿真方法,分析微流体中细胞筛选的影响因素。基于层流、流体流动粒子追踪、波动光学理论,利用有限元分析法建立了一种交叉型光学颗粒分离模型,研究了利用光压差分技术分离细胞的各种影响因素,其中包括微粒直径,激光功率、温度、光纤直径,分析了微粒在流体中因光辐射压力作用下的偏移距离。实验结果表明:在微流体中,激光功率、细胞直径、温度(20℃)和偏移距离大体上成正比关系,光纤直径和细胞直径在大小相当的情况下光辐射压力能够达到最大值,当激光通过光纤作用于直径分别为3,8和20μm的微粒时,光纤直径为7μm或8μm时光辐射压力最大,所以选用直径为8μm的单模光纤作为一个重要的实验光学器件。所得结论为深入研究细胞筛选影响因素的数值仿真精度提供了参考与借鉴。     

Manufacturing process of copper microgrooves utilizing a novel optical fiber-based laser-induced etching technique

A new approach for the fabrication of copper microgrooves with near triangular cross-sectional profile is introduced. For manufacturing the microgrooves, a laser-induced thermochemical etching technique based on an optical fiber as an optical waveguide and machining tool is proposed, which significantly reduced the complexity of a conventional laser etching set up. It is explained that the possible problem of fiber damage during laser etching with the proposed method can be solved by appropriately controlling the gap between the sample surface and fiber tip. The fabrication of copper microgrooves with 100 ∼ 300 μm in depth and 100 ∼ 150 μm in width is accomplished with the proposed technique. The grooves fabricated in the optimal process condition have smooth surfaces and clear edge. The angle of triangular groove is measured to be in the range of 30 ∼ 50 degree and the aspect ratio of grooves is about 1 ∼ 2. The overall etching results such as etch width, depth, and aspect ratio variation are reported in detail with respect to process variables.     

Wide angle near-field optical probes by reverse tube etching

We present a simple modification of the tube etching process for the fabrication of fiber probes for near-field optical microscopy. It increases the taper angle of the probe by a factor of two. The novelty is that the fiber is immersed in hydrofluoric acid and chemically etched in an upside-down geometry. The tip formation occurs inside the micrometer tube cavity formed by the polymeric jacket. By applying this approach, called reverse tube etching, to multimode fibers with 200/250 microm core/cladding diameter, we have fabricated tapered regions featuring high surface smoothness and average cone angles of approximately 30 degrees . A simple model based on the crucial role of the gravity in removing the etching products, explains the tip formation process.     

激光干涉微轮廓测量仪

基于Michelson干涉仪测量原理研制的微轮廓测量仪,载物平台采用步进电机和压电陶瓷(PZT)两级闭环驱动与定位,步进电机用于快速粗定位和扩大测量范围,压电陶瓷用于精密定位,重复定位精度为10 nm;测量光路采用共干涉系统,对机械振动,温度漂移不敏感;测量范围20 mm×20 mm×0.4 mm,纵向分辨率为0.32 μm,横向分辨率为0.5μm.     

柔性再生碳纤维湿法取向仿真模拟及其复合材料性能研究

基于珠链模型,采用离散单元法对纤维模型进行柔性化处理;通过搭建EDEM-Fluent耦合仿真模型,对柔性再生碳纤维在渐缩流场中的流动取向过程进行仿真模拟。采用湿法取向技术对6 mm纤维进行重新取向排布制备取向毡,将仿真结果与实验结果进行对比。采用模压法制备了碳纤维/环氧树脂基复合材料,对其力学性能进行表征。结果表明：在纤维跟随流体运动的过程中,纤维会受到轴向剪切力的作用,发生不同程度的弯曲变形,并沿着流体流动方向发生旋转,从而在移动过程中完成取向。利用二维方向张量对纤维毡取向度进行表征,其取向度为98%;制备的取向复合材料弯曲强度和模量较未取向材料分别提升70.6%和88.5%。     

光纤石英玻璃基板微V槽阵列的精密磨削

针对脆性石英玻璃的微加工,利用自主研发的金刚石砂轮微尖端修整工艺,研发了光纤阵列石英玻璃微V槽磨削技术。分析了60°的微V槽形状偏差对光纤耦合损耗的影响,然后,研究了砂轮微尖端的误差补偿修整工艺。最后,实验分析了微V槽的磨削精度。理论分析显示:微V槽角度、间距和宽度的偏差分别控制在±0.42°、±1.04μm和±1.2μm以内时,耦合损耗小于0.5dB。实验结果表明:开发的数控磨削工艺可加工高精度的60°微V槽阵列;采用数控轨迹和角度补偿修整后,砂轮微尖端半径可平均达到10.46μm,角度精度为(60±0.22)°;对石英玻璃进行微磨削后,微V槽的角度偏差达到0.4°,尖端半径为10.5μm,宽度偏差为0.3μm,间距偏差为0.5μm,可保证光纤阵列的精密对接。     

Feedback-controlled laser fabrication of micromirror substrates

Short (40-200 μs) single focused CO(2) laser pulses of energy ?100 μJ were used to fabricate high quality concave micromirror templates on silica and fluoride glass. The ablated features have diameters of ≈20-100 μm and average root-mean-square (RMS) surface microroughness near their center of less than 0.2 nm. Temporally monitoring the fabrication process revealed that it proceeds on a time scale shorter than the laser pulse duration. We implement a fast feedback control loop (≈20 kHz bandwidth) based on the light emitted by the sample that ensures an RMS size dispersion of less than 5% in arrays on chips or in individually fabricated features on an optical fiber tip, a significant improvement over previous approaches using longer pulses and open loop operation.     

分光测色仪中的光谱仪系统

根据分光测色仪的应用需要,对分光系统、光电接收系统及相关电路组成的光谱仪进行了模块化设计,以方便仪器的整体设计、装调和测试。考虑分光测色仪是非成像光学仪器,故提出用光纤来连接各光学模块。根据应用需求提出了光谱仪的主要技术指标,所设计光谱仪很好地完成了球差和彗差的校正。分析了用滤光片消除二级衍射光谱的方法,解决了光纤和光谱仪数值孔径不匹配的问题。研制了光谱仪系统,其外形尺寸为130mm×90mm×45mm。实验测试显示,在狭缝宽度为50μm时,光谱仪各波段的光谱分辨率都可以达到2nm。对光谱仪进行了波长定标,定标精度小于0.2nm,整个工作波段占401个像元,满足1nm的波长输出间隔的设计要求。该光谱仪的可弯曲光纤和电子线路便于整机灵活布局与模块拆卸,同时方便单独测试。所述方法为分光测色仪的整机研制与测试打下了良好的基础。