光纤色散法测量闪烁体脉冲光谱

提出了一种利用光纤波长色散测量脉冲光谱的方法.由于具有较宽光谱的脉冲光在一定长度的光纤中传播时会发生波形展宽,需要根据测量和标定结果校正展宽的波形才能得到光源的实际光谱曲线.标定时首先利用ps级脉冲光源对测量系统进行时间响应标定,得到系统的时间响应函数;接着测量不同波长光的走时,得到不同波长的群折射率;最后测量光纤中的光谱衰减,得到各种波长的相对衰减或传输效率.利用以上3个标定结果,对波形进行数字逆卷积,并进行走时校正和衰减系数校正,即可对所得到的波形进行恢复.经实验测量和数据处理,得到了一种红光闪烁体的发光光谱曲线,其中心波长与用其他方法测到的中心波长的差小于2 nm,谱线形状基本一致.研究显示,在脉冲光的脉冲宽度远小于其色散展宽时,可以利用光纤的波长色散对脉冲光的光谱进行测量.     

The dispersion of some optical properties of vitrinite

The dispersion characteristics of some optical properties of vitrinites from a number of coals of differing coal rank and type were investigated using a microscope photometer. The properties studied were air and oil reflectances, refractive index and absorption index. The technique employed involved the measurement of air and oil reflectances at a number of wavelengths in the visible spectrum for selected points on the coal, as opposed to averaging the reflectances obtained in each immersion medium for each wavelength. The values of air and oil reflectances were then used to calculate the corresponding values of refractive index (n) and absorption index (κ) using a rearrangement of Beer's equation. Smooth dispersion curves were obtained for each selected field of vitrinite using this procedure. This method was preferred to the more widely used method of calculating n and κ from the average air and oil reflectances at each wavelength, because refractive and absorption indices are non-linear functions of reflectance, which makes the arithmetic mean of the reflectances unsuitable for the calculation of n and κ. The values of all parameters for the vitrinites were found to increase towards the blue region of the visible spectrum and to increase at all wavelengths with increasing coal rank. Some negative values of κ² were obtained and the significance of these values is discussed.     

A new high-aperture glycerol immersion objective lens and its application to 3D-fluorescence microscopy

High‐resolution light microscopy of glycerol‐mounted biological specimens is performed almost exclusively with oil immersion lenses. The reason is that the index of refraction of the oil and the cover slip of ~1.51 is close to that of ~1.45 of the glycerol mountant, so that refractive index mismatch‐induced spherical aberrations are tolerable to some extent. Here we report the application of novel cover glass‐corrected glycerol immersion lenses of high numerical aperture (NA) and the avoidance of these aberrations. The new lenses feature a semi‐aperture angle of 68.5°, which is slightly larger than that of the diffraction‐limited 1.4 NA oil immersion lenses. The glycerol lenses are corrected for a quartz cover glass of 220 µm thickness and for a 80% glycerol‐water immersion solution. Featuring an aberration correction collar, the lens can adapt to glycerol concentrations ranging between 72% and 88%, to slight variations of the temperature, and to the cover glass thickness. As the refractive index mismatch‐induced aberrations are particularly important to quantitative confocal fluorescence microscopy, we investigated the axial sectioning ability and the axial chromatic aberrations in such a microscope as well as the image brightness as a function of the penetration depth. Whereas there is a significant decrease in image brightness associated with oil immersion, this decrease is absent with the glycerol immersion system. In addition, we show directly the compression of the optic axis in the case of oil immersion and its absence in the glycerol system. The unique advantages of these new lenses in high‐resolution microscopy with two coherently used opposing lenses, such as 4 Pi‐microscopy, are discussed.     

Modern techniques in reflectance measurements

In the field of quantitative investigation of microscopic images reflectance measurements with the aid of photoelectric equipment play an important role. Reflectances can be used for the identification of various components in a polished specimen, for chemical analysis and for the determination of the refractive index of a specimen as well as for a determination of the various absorption parameters of reflecting solid material. The parameters involved are: reflectances at given wavelengths, spectral reflectance curves in the visible, UV-, and near IR-spectral range, reflectances of optically anisotropic surfaces at varying orientations of the vibration plane of linearly polarized light, reflectances in air and in an immersion liquid (mainly in standard immersion oil). From spectral curves, quantitative expressions of colour can be derived. Due to improvements in reflectance standard materials and technical design of apparatus the measurements and calculations can be carried out very conveniently, quickly and precisely.     

Variable wavelength microinterferometry of textile fibres

A specific microinterferometric method, referred to as variable wavelength interferometry (VAWI), and its object-adapted version (AVAWI) are proposed for measuring the spectral dispersion of birefringence and/or spectral dispersion of the refractive indices n and n⊥ of textile fibres. The method uses monochromatic light with variable wavelength (Λ). The only parameters that are directly measured are the inter-fringe spacings (b) and the fibre thickness (or diameter), while other quantities are observed, read from the calibration graph b(Λ), and derived from quite simple formulae. A double-refracting interference microscope fitted with a tungsten-halogen lamp (12 V/100 W) and a wedge interference filter are used. No liquid immersion is required, and the fibre under study can simply be surrounded by an air medium. Results of measurements made on PPT and PA-6 fibres are given as an example.     

Aberration characteristics of immersion lenses for LVSEM

This paper investigates the on-axis aberration characteristics of various immersion objective lenses for low voltage scanning electron microscopy (LVSEM). A simple aperture lens model is used to generate smooth axial field distributions. The simulation results show that mixed field electric-magnetic immersion lenses are predicted to have between 1.5 and 2 times smaller aberration limited probe diameters than their pure-field counterparts. At a landing energy of 1 keV, mixed field immersion lenses operating at the vacuum electrical field breakdown limit are predicted to have on-axis aberration coefficients between 50 and 60 microm, yielding an ultimate image resolution of below 1 nm. These aberrations lie in the same range as those for LVSEM systems that employ aberration correctors.     

分光光度计光强采样电路设计

分光光度计是用于测量物质在不同波长光的透过率和吸收率等参数的仪器。由于光源和硅光二极管在不同波长下的特性差别很大 ,使得检测出的信号具有较大的动态范围 ,且在 335 nm处信号非常微弱。介绍测量分光光度计光强采样电路的设计方案 ,该电路具有简洁 ,可靠性高等优点     

可调谐锁模光纤激光器泵浦的超连续谱光源

为了实现平坦度更好、光谱覆盖可见光波段的超连续谱激光输出,研究了泵浦波长可调谐的全光纤结构超连续谱光纤激光器。设计搭建了一台非线性偏振旋转锁模脉冲光纤激光器,实现了9种中心波长的耗散孤子皮秒脉冲输出,波长调谐范围为1 041~1 076nm;以它作为种子源进行了两级功率放大,并泵浦10m长的光子晶体光纤,在泵浦激光功率为500mW时,得到9种输出光谱特性不同的超连续谱激光,得到当泵浦激光中心波长为1 050nm时,更利于实现光谱范围更宽、平坦度更好、可见光分量更多的超连续谱激光输出。为进一步拓宽超连续谱激光的光谱范围、提升光谱平坦度,将泵浦激光功率提升至1.45 W,最终实现了输出功率为600mW、短波边界为470nm、600~1 700nm内10dB光谱宽度为1 053nm的超连续谱激光输出。     

小型的高精度软X射线-极紫外反射率计

针对探月二期工程中的有效载荷之一极紫外相机中的多层膜光学元件高精度反射率测量的需要,建立了一台使用液体靶激光等离子体光源的小型软X射线-极紫外波段反射率计。该反射率计主要由激光等离子体光源、Mcpherson 247动狭缝掠入射单色仪及相关的数据采集系统组成。单色仪波段范围1-125nm,光谱分辨率小于0.08nm。无碎屑的液体靶激光等离子体光源的使用避免了光学元件的损坏,而动狭缝掠入射单色仪的使用则提高了光谱分辨率和波段范围。使用该反射率计实测了工作波长为13.5nm和30.4nm的Mo/Si多层膜的反射率,测量结果表明测量重复性优于±0.5%。     

Hilbert diagnostics of phase disturbances of the light field induced by a vortex flow

Methods of Hilbert filtration of phase disturbances of the light field in the spectral range of source emission are discussed. The evolution of complementary vortex rings induced in an air medium by a pressure pulse on the hole in the combustor wall under various boundary and initial conditions is experimentally studied.     

无限共轭距物镜的数值孔径全自动测量方法与系统

提出了一种针对无限共轭距显微物镜的数值孔径测量方法,采用载玻片与空气界面处的全反射效应以及其在物镜的后焦面产生的全反射圆作为数值孔径参考基准,根据阿贝正弦定理推导出物镜的数值孔径。完成了基于该原理的实验测试系统的研发,包括光学系统、控制系统和完整的后焦面算法流程。其中的图像处理算法采用了二维傅立叶相关分析和灰度统计。对若干实际的油浸物镜的数值孔径进行了测量,结果表明本方法相对误差低于1%,远低于本文对比的其它方法。本方法对应的实验测量装置简单,可快速、全自动化地对实际的油浸物镜的数值孔径进行测量,且测量结果具有高精度和高重复性的优势,能直接用于无限共轭距油浸物镜的数值孔径测量,解决当前制约我国高端镜头检测方面的困难,具有很好的应用前景。     

A twisted periscope arrangement for transporting elliptically polarized light without change in its polarization state

The authors describe a dual-mirror 90(°) twisted periscope arrangement for transporting polarized light in air, wherein a general elliptic polarization state of the light is preserved at all wavelengths. It is experimentally demonstrated that in the wavelength range 400-1000 nm, this arrangement preserves the polarization state fairly well when using either metallic or dielectric mirrors.     

半球形和超半球形固体浸没透镜光场分布比较

考虑了在固体浸没透镜(SIL)的球面表面的反射,应用矢量衍射理论比较分析了半球形固体浸没透镜(h-SIL)和等光程的超半球形固体浸没透镜(s-SIL)的透射场分布。h-SIL和s-SIL的分辨力、焦深、聚焦强度和随波长的色散被详细比较。计算结果发现:当它们被包围在空气中时,s-SIL的分辨力比h-SIL的大n倍以上(n是SIL的折射率);s-SIL的聚焦强度比h-SIL的大,但它的焦深比较小。s-SIL的横向色散率远大于h-SIL的,但h-SIL的轴向色散率与s-SIL的几乎相等。h-SIL的横向色散很小,可以忽略不计。     

Multispectral imaging of the ocular fundus using light emitting diode illumination

We present an imaging system based on light emitting diode (LED) illumination that produces multispectral optical images of the human ocular fundus. It uses a conventional fundus camera equipped with a high power LED light source and a highly sensitive electron-multiplying charge coupled device camera. It is able to take pictures at a series of wavelengths in rapid succession at short exposure times, thereby eliminating the image shift introduced by natural eye movements (saccades). In contrast with snapshot systems the images retain full spatial resolution. The system is not suitable for applications where the full spectral resolution is required as it uses discrete wavebands for illumination. This is not a problem in retinal imaging where the use of selected wavelengths is common. The modular nature of the light source allows new wavelengths to be introduced easily and at low cost. The use of wavelength-specific LEDs as a source is preferable to white light illumination and subsequent filtering of the remitted light as it minimizes the total light exposure of the subject. The system is controlled via a graphical user interface that enables flexible control of intensity, duration, and sequencing of sources in synchrony with the camera. Our initial experiments indicate that the system can acquire multispectral image sequences of the human retina at exposure times of 0.05 s in the range of 500-620 nm with mean signal to noise ratio of 17 dB (min 11, std 4.5), making it suitable for quantitative analysis with application to the diagnosis and screening of eye diseases such as diabetic retinopathy and age-related macular degeneration.     

Acousto-optic modulator system for femtosecond laser pulses

Femtosecond laser pulses have made a revolution in multiphoton excitation microscopy, micromachining, and optical storage for their unprecedented high peak power. However, modulation of their intensity with acousto-optic modulator (AOM) is frustrated by dispersion which results in a significant stretch in pulse width. Here we report a scheme composed of two acousto-optic deflectors (AODs) to modulate the intensity of the femtosecond laser pulses with simultaneous compensation for the temporal dispersion. With commercial AODs, we demonstrated such an AOM system for the femtosecond laser pulses with overall transmission efficiency of around 80%. The pulse width of the exit beam is 115-177 fs for an input pulse of 110 fs, across the wavelength range of 720-920 nm when the temporal dispersion compensation is optimally tuned at 800 nm. The fluorescence intensity in a two-photon microscopy experiment performed using this system increased 5.5-fold over that of the uncompensated AOM.     

激光等离子体软X线光源的研究

本文设计了一种高精度旋转靶系统的激光等离子体软X线光源,亮度高,强度大,光斑尺寸(100～200)μm,脉冲时间几十纳秒,可以辐射出直至软X线的连续光谱及迭加在连续光谱之上的线光谱,峰值波长位于(13～17)nm。在多次测量取平均的方式下,其稳定性和重复性优于±4.5%。     

基于光子晶体光纤参量振荡器的CARS成像光源研究

研究了一种基于光子晶体光纤参量振荡器的相干反斯托克斯拉曼散射(CARS)成像光源。该光源采用中心波长为1 030nm的皮秒光纤激光器作为泵浦源,以无截止单模光子晶体光纤作为参量增益,通过搭建光参量振荡器,实现平均功率为10mW的参量激光输出。在色散滤波效应的作用下,该光源输出波长可实现连续可调,调谐范围为782～793nm,对应的波数覆盖范围为2 901～3 078cm-1。该光源产生的两束激光脉冲可实现空间自同步、时间自重合,用于CARS成像测量时,无需空间、时间对准,有望推动CARS成像光源向全光纤化、小型化的方向发展。     

Detection of dust on JET with the high resolution Thomson scattering system

Dust particles have been observed with Thomson scattering systems on several tokamaks. We present here the first evidence of dust particles observed by the new high resolution Thomson scattering system on JET. The system consists of filter spectrometers that analyze the Thomson scattering spectrum from 670 to 1050 nm in four spectral channels. The laser source is a 5 J Q-switched Nd:YAG laser. Without a spectral channel at the laser wavelength, only dust particles that emit broadband light could be detected; these particles have been observed on JET after disruptions. The timing of their emission is clearly different from that expected for a Thomson scattering pulse. The light pulse from dust happens after the peak of the laser light and has a long tail.     

一种新的光学相干层析成像中色散现象的补偿方法

光学相干层析成像技术中,样品的色散特性将降低获取图像的分辨力。通过实验获取了不同色散特性的样品的相干图像。实验采用中心波长为845nm,频谱宽度为26nm的超辐射光源。实验的样品为一块30mm厚的BK 7玻璃。根据光源的频谱信息和样品的色散系数,理论计算了OCT信号的包络,并与实验中测得的信号相对比。同时提出了一种新的数值方法,来补偿样品的色散。该方法可在时域或者频域OCT中方便地应用。通过实验验证了该方法的可行性。     

快速光谱光度计的研制

基于多通道技术和脉冲照明光源,采用自扫描光电二极管阵列(SPD)作为光电探测器,研制成快速的光谱光度计。经过精密的波长定标和光谱反射比定标,在专用PC计算机控制下结合软件功能,实现对物体表面色的快速高精度测量。