磁光成像无损检测方法的研究现状与展望

随着工业发展对智能化、无污染、高效率的需求,无损检测技术在工业中的应用是目前各国的研究重点。在此基础上,磁光成像检测将成为无损检测领域的主要方法之一。概述了国内外无损检测的发展现状,简单介绍了工业领域常用的无损检测方法;详细介绍了磁光成像检测技术的基本原理、激励方式、磁光薄膜和磁光图像处理方法,并分别对其发展现状和趋势作了归纳分析,包括国外磁光传感器成品的简介。此外,概述了磁光成像检测方法在航空航天业、工业铸锻焊件、激光焊接焊缝跟踪及光学器件制作中的应用;同时展望了磁光成像检测技术的发展方向。     

磁光薄膜电流传感器

磁光薄膜电流传感器，是基于磁致旋光介质在外磁场的作用下，对偏振光振动面的旋光原理、光导纤维对高压电场的隔离特性而设计的一种新型电流传感器。它可用于低压、高压和超高压配电网中，对直流、交流进行实时遥测和故障定位。     

全变分法恢复焊缝磁光图像质量分析

在利用磁光传感器检测焊缝位置时,因为受到试验环境的影响,采集的焊缝图像会出现图像降质现象,对微间隙焊缝进行准确检测造成困难,因此需对焊缝磁光图像进行图像恢复处理。采用全变分法图像恢复模型,分析图像恢复质量,结果表明,此模型能在降噪的同时,保持焊缝图像良好的细节特征。     

稀土石榴石磁光传感的研究

磁光传感是研究应用介质的法拉第效应检测外界磁场和电流的一种新型传感技术。本文研究的光纤磁光传感系统以稀土石榴石单晶薄膜为磁光介质。可检测≤10mT 的交直流磁场及相应的电流。线性度≤±1.5%,误差≤1.5%(满度)。     

微间隙焊缝磁光成像检测及跟踪方法

在激光对接焊过程中,必须精确检测焊缝位置并控制激光束始终对中焊缝。针对小于0.05 mm的微间隙对接焊缝,通过对焊件施加感应磁场,利用法拉第磁旋光原理构成磁光传感器,获取焊缝磁光图像。针对焊缝磁光图像,以焊缝磁光图像的灰度直方图为特征模版,研究一种基于均值漂移算法的激光焊焊缝检测与跟踪方法。通过均值漂移与粒子滤波相结合的算法,利用粒子滤波能够对图像大范围搜索目标的特点,实现焊缝全自动跟踪。同时,根据相似度Bhattacharyya系数对焊缝特征模版进行更新,提高焊缝跟踪精度。试验结果表明,利用均值漂移与粒子滤波相结合的算法能够从焊缝磁光图像中有效检测焊缝特征,实现焊缝的自动跟踪。     

光通信用磁光材料的研究进展

综述并分析了磁光玻璃、晶体和薄膜3类磁光材料的影响因素、制备工艺、性能和研究现状,并分别将3类磁光材料的研究成果列表对比。重点介绍了磁光晶体YIG的生长工艺因RoHS的实施而向无铅化发展的情况和掺杂稀土铁石榴石在光通信波段中的性能优势和工艺瓶颈。最后对光通信用磁光材料的未来发展趋势进行了展望。     

磁光玻璃专用高温炉设计

磁光玻璃专用高温炉是一种新型实验室高温炉,分为上下两部分,上部熔化搅拌,自动浇注,下部退火,整个过程处于高温环境,且相对隔绝了空气污染,提高了磁光玻璃熔化成型的质量,有效消除磁光玻璃中的气泡,条纹等缺陷,有利于提高磁光玻璃的Verdet常数和增大磁光玻璃的尺寸。     

氦光泵磁敏传感器共振信号模拟装置设计

氦光泵磁敏传感器和检测系统共同实现对磁场的测量。验证检测系统能否正常工作的传统方法是制作出整个传感器后进行调试。针对检测系统的可行性验证,设计了共振信号模拟装置。产生的磁共振信号能够模拟光学系统的功能,通过调制域测频实现了对检测系统反馈信号的实时测量。实验测试表明,该装置能够验证检测系统的可行性,其性能十分接近氦光泵磁敏传感器,并且具有测量精度高、实时性好、稳定可靠、不依赖工作环境、制作成本低等特点。     

磁光旋转谱和磁圆二向色性谱测量

本文描述了磁光旋转谱和磁圆二向色性谱测试装置的基本特性,用该装置测量了(BiTm)_3(FeGa)_5O_(12)薄膜磁光旋转θ的实部θ′和虚部θ″与光波长λ的关系,不同λ情况下YIG单晶的θ′与磁场强度H 的关系。讨论了测试结果,分析了测量误差。指出用磁光诃制倍频法测量磁光旋转谱和磁圆二向色性谱基本上不受激光源幅度变化和光路中其他元器件不稳定因素的影响,在λ=0.65～2.7μm 范围内,测量θ′的重复精度可达±0.005°。     

微间隙焊缝磁光成像卡尔曼滤波跟踪算法

在激光对接焊过程中,实时控制激光束准确对中焊缝是保证焊接质量的前提。针对紧密对接激光焊,研究一种用于微间隙(不大于0.1 mm)焊缝位置识别及跟踪的磁光成像卡尔曼滤波算法。采用磁光传感器实时获取焊接区域的微间隙焊缝磁光图像序列,利用微间隙焊缝磁光图像的灰度梯度特征提取焊缝位置坐标。以焊缝位置及位移量构成状态矢量,建立描述焊缝位置的状态方程和测量方程。同时,假设系统动态噪声和测量噪声为零均值随机分布的高斯白噪声,建立噪声环境下的卡尔曼滤波跟踪算法,计算最小均方差条件下焊缝中心最优预测值,减小系统噪声和过程噪声对焊缝位置测量的影响。试验结果显示,该方法能有效实现激光对接焊微间隙焊缝位置的识别与跟踪。     

焊接缺陷磁光成像动态检测与识别

为了实现焊接缺陷的自动检测,研究一种交变磁场激励下焊缝表面及亚表面缺陷的磁光成像动态无损检测方法。分析了基于法拉第磁致旋光效应的焊接缺陷磁光成像机理,并结合交变磁场原理推导出励磁变化与动态磁光成像的关系。探索低碳钢板的亚表面焊缝磁光成像特征试验,验证了所提方法可用于检测焊缝亚表面的未熔合缺陷。最后对高强钢焊缝特征的动态磁光图像进行分析,采用主成分分析法和支持向量机(PCA-SVM)模式识别方法建立了焊接缺陷分类模型。试验结果表明,所提方法可以识别高强钢焊件中的焊缝特征(未熔透、裂纹、凹坑和无缺陷),缺陷分类模型的整体识别率达到92.6%,能够实现焊缝表面及亚表面缺陷的自动检测。     

Note: Investigation of atom transfer using a red-detuned push beam in a double magneto-optical trap setup

We present our results on transfer of cold (87)Rb atoms from a vapor cell magneto-optical trap to ultrahigh vacuum magneto-optical trap (UHV-MOT) using a red-detuned continuous wave push beam in a double-magneto-optical trap setup. We find that use of retro-reflected red-detuned push laser beam results in higher number in UHV-MOT than the number obtained without retro-reflection of push beam.     

Detection of micro gap weld using magneto-optical imaging during laser welding

Accurate seam tracking plays a critical role in acquisition of good weld. During laser butt joint welding, the laser beam focus must be controlled to follow the weld trajectory. The key problem to be solved is the automatic identification of weld position. An approach to detect the micro gap weld (gap width is less than 0.05 mm) based on magneto-optical imaging (MOI) is proposed. The laser butt joint welding of carbon steel was carried out. A magnetic excitation device was used to magnetize the weldment, and it was found that magnetic field distribution at the weld was different from other regions. The magnetized weldment was detected by using a magneto-optical sensor, and magneto-optical images of the weld were captured. By analyzing and processing weld MO images with low contrast and strong magnetic field noises, the weld center position could be detected accurately. Weld MO images at different laser welding speeds were investigated to analyze the varieties of image characteristics. Experimental results indicated that the magneto-optical imaging technique could be applied to detect the micro gap weld accurately, which provides a novel approach for automatic identification and tracking of micro gap weld during laser welding.     

Near-field magneto-optical analysis in reflection mode SNOM

Observation of magnetic domains with in-plane magnetisations is demonstrated by scanning near-field optical microscopy (SNOM) in reflection mode. The longitudinal and transverse magneto-optical Kerr effects are employed as the contrast mechanisms; these are observed as either a change in the polarisation of the reflected light or reflectance, depending on magnetisation direction. SNOM images of Co and Ni thin films show magneto-optical contrast depending on polarisation of the incident and detected light. For the smooth cobalt thin films, the orientation for magnetic domains is estimated, based on the correlation between the contrasts in SNOM images obtained in different polarisation configurations and the directions of the magnetic vectors of the incident and reflected light. For the nickel films with pronounced topographic structures, the resulting near-field polarisation dependencies are more complicated, suggesting that the magneto-optical contrast in SNOM images are affected by the topographic cross-talk due to the depolarisation effects on surface topographic features.     

Apparatus for vectorial Kerr confocal microscopy

We present a confocal microscopy setup that is able to record magneto-optical hysteresis cycles separating the in-plane and out-of-plane magnetization components. This apparatus is based on a modified commercial microscope, where the light beam has been deviated from the cylindrical symmetry axis of the objective lenses by inserting a translating plate in the optical path. The instrument allows for the magneto-optical imaging with a lateral resolution of 600 nm at λ = 635 nm light wavelength.     

Versatile cold atom target apparatus

We report on a compact and transportable apparatus that consists of a cold atomic target at the center of a high resolution recoil ion momentum spectrometer. Cold rubidium atoms serve as a target which can be operated in three different modes: in continuous mode, consisting of a cold atom beam generated by a two-dimensional magneto-optical trap, in normal mode in which the atoms from the beam are trapped in a three-dimensional magneto-optical trap (3D MOT), and in high density mode in which the 3D MOT is operated in dark spontaneous optical trap configuration. The targets are characterized using photoionization.     

SPR谱仪的研制及在磁光复合薄膜测试中的应用

针对SPR增强磁光效应研究中复合金属薄膜结构的SPR激发测试,研制了一套角度扫描型SPR谱仪。通过巧妙的结构设计和运动控制,使得角度扫描过程中样品测试点始终处于棱镜底面样品基片的中心,保证了测试过程的一致性。对50nm金膜的重复性测验表明SPR谱仪具有较高的重复性和稳定度。利用搭建的SPR谱仪对磁光复合薄膜的测试结果表明,在制备的样品中,Au(15nm)/Co(5/10nm)/Au(5nm)复合结构是磁光等离子体系研究的最佳平台。     

Magneto-optical system for high speed real time imaging

A new magneto-optical system has been developed to expand the range of high speed real time magneto-optical imaging. A special source for the external magnetic field has also been designed, using a pump solenoid to rapidly excite the field coil. Together with careful modifications of the cryostat, to reduce eddy currents, ramping rates reaching 3000 T∕s have been achieved. Using a powerful laser as the light source, a custom designed optical assembly, and a high speed digital camera, real time imaging rates up to 30 000 frames per seconds have been demonstrated.