基于白光干涉法测量微光栅形貌及相关几何参量的研究

基于显微白光干涉术,利用扫描干涉显微镜对四台阶面阵微光栅记录了128幅白光干涉图,并分别运用重心法、空间频域算法、移相算法及包络曲线拟合法对扫描干涉图进行了分析处理。被测微光栅的形貌及周期在各算法下均完全吻合,台阶总高最大相差0.8%。同时,用美国Veeco白光轮廓仪对同一样品的形貌及光栅周期进行了测试,数据显示两者结果非常吻合,仅台阶总高相差0.7%。研究结果表明,所采用的四种算法均适用于微观三维形貌的测量。     

Real-time displacement measurements with a Fabry-Perot cavity and a diode laser

We present the basic operating principles of a traceable measurement system suitable for use with atomic force microscopes (AFMs) and nanometer-resolution displacement sensors. Our method is based upon a tunable external-cavity diode laser system which is servo-locked via a phase-modulated heterodyne locking technique to a Fabry-Perot interferometer cavity. We discuss mechanical considerations for the use of this cavity as a displacement metrology system and we describe methods for making real-time (sub 10 ms sampling period) measurements of the optical heterodyne signals. Our interferometer system produces a root-mean-squared (RMS) displacement measurement resolution of 20 pm. Two applications of the system are described. First, the system was used to examine known optical mixing errors in a heterodyne Michelson interferometer. Second, the Fabry-Perot interferometer was integrated into the Z axis of a commercial AFM scanning stage and used to produce interferometer-based images of a 17 nm step height specimen. We also demonstrate atomic resolution interferometer-based images of a 0.3 nm silicon single atomic step-terrace specimen.     

Form Error Characterisation by an Optical Profiler

Form errors are deviations of the machined surface from the geometrical surface excluding position errors, waviness and roughness. From a functional point of view, as for surface roughness, form error characterisation is also important. In the present work, an optical profiler is used to measure and numerically characterise form errors such as roundness and cylindricity of cylindrical surfaces. A double orientation method using mean value analysis has been applied to separate the workpiece error from the spindle error during roundness measurement. Software is developed for data generation, fitting the reference data for assessing form errors in terms of statistical and functional parameters including new parameters. An optical profiler measures all the surface irregularities and hence can be used to study both micro and macro errors of the profile measured. A study of both roughness and roundness parameters along the circumferential direction is made for the unfiltered signal using different filter cut-off values. It is known that filtering greatly affects the value of the form error parameters measured. The form measurements obtained by the optical profiler are compared with the stylus profiler and the results are presented.     

Measurements of dimensional standards and etalons with feature size from tens of micrometres to millimetres by using sensor strengthened nanomeasuring machine

A laser focus sensor and a contact inductive sensor have been coupled to an ultra high precision positioning stage, referred to as a nanomeasuring machine (NMM), for measurements of dimensional standards with a large measurement volume of 25 mm × 25 mm × 5 mm. Control and measurement software have been designed and complemented. The measurement uncertainty of strengthened NMM has been analyzed and discussed. Groove depth and step height standards with feature heights of tens of micrometres to millimetres as well as aspherical surface etalons are calibrated by nanomeasuring machine. The paper also introduces a method for characterising the measured aspheric surface by least square fitting the measured data to a quadratic paraboloid function. The obtained quadratic coefficients are compared to that measured by a conventional coordinate measuring machine (CMM) and a stylus profiler, showing a good agreement.     

Exact reconstruction method for on-machine measurement of profile

We present a new reconstruction method for measuring profile of large, ultraprecise absolute optical surfaces with a compact interferometer. The profile of workpiece can be reconstructed exactly with high lateral resolution and large non-equidistant scanning step. Both systematic errors of the interferometer and height offsets of the scanning stage can be eliminated. Additional angular measurement can be used to measure pitching angles of the scanning stage. The exact reconstruction method is verified by computer simulation and on-machine measurement experiment.     

基于原子力显微镜的薄膜厚度检测系统

研制了一种基于原子力显微镜的薄膜厚度检测系统。该系统首先绘制薄膜轮廓曲线,根据曲线找到薄膜边界,然后计算镀膜区与无膜区的高度差,得到薄膜厚度。跟台阶仪、光学轮廓仪相比,该系统具有操作简单、抗干扰能力强、精度高的优点。实验表明。该系统有很高的重复性,能够精确测量各种不同性质的薄膜的厚度。     

Micro optical power meter for direct in situ measurement of light transmitted from microscopic systems and focused on micro-samples

This paper reports a micro optical power meter which is able to perform effective and precise measurement on the optical power at the focus of different microscopic systems. The power meter can be easily placed on the stages of different microscopes and even partly immersed into solution to directly measure the optical power transmitted from the microscope objective and focused on the sample suspended in solution. The testing experiments demonstrated that the power meter has the characteristics of high precision, excellent linearity, high sensitivity, good stability, and high responding speed. It can accurately measure power levels from 0.1 to 50 mW in visible wavelength in various conditions and environments, which may encounter in practical applications. The optical power measurements using the power meter performed in some biological cell culturing solutions and in air for the same laser light reveal the first time that the powers measured in solutions were about 5%-8% greater than that measured in air at the same position. This not only suggests the necessity of performing direct measurement in situ in solution to obtain the real optical power projected on the suspended samples, but also indicates that such a micro optical power meter can meet almost all the requirements of optical power measurement in different fields from biomedicine to material sciences.     

Application of a portable measuring system with acoustic Doppler current profiler to discharge observations in steep rivers

Obtaining discharge measurements during high flows is very difficult in steep rivers (slopes greater than about 0.1%) because of the highly unstable free surfaces and bed elevations. In this study, a portable flow measuring system with an acoustic velocimeter was developed. The proposed system has been proved to be better than existing systems for streamflow measurements in steep rivers. Field data collected by conventional velocimeters were analyzed, and compared with the flow measurements using the portable system with an ADP (acoustic Doppler profiler) or ADCP (acoustic Doppler current profiler). The effects of channel patterns on the applicability of the highly efficient discharge estimation method, as proposed by C.L. Chiu [An efficient method of discharge measurement in rivers and streams. In: Lecture of the workshop for development and application of discharge measurement in Taiwan. Taichung (Taiwan): National Chung-Hsing University, 1996. p. 55 [in Chinese]], were also discussed. In general, the method was applicable to higher flows where the measuring verticals were reasonably stable.     

Precision of light intensity measurement in biological optical microscopy

Standardization and calibration of optical microscopy systems have become an important issue owing to the increasing role of biological imaging in high‐content screening technology. The proper interpretation of data from high‐content screening imaging experiments requires detailed information about the capabilities of the systems, including their available dynamic range, sensitivity and noise. Currently available techniques for calibration and standardization of digital microscopes commonly used in cell biology laboratories provide an estimation of stability and measurement precision (noise) of an imaging system at a single level of signal intensity. In addition, only the total noise level, not its characteristics (spectrum), is measured. We propose a novel technique for estimation of temporal variability of signal and noise in microscopic imaging. The method requires registration of a time series of images of any stationary biological specimen. The subsequent analysis involves a multi‐step process, which separates monotonic, periodic and random components of every pixel intensity change in time. The technique allows simultaneous determination of dark, photonic and multiplicative components of noise present in biological measurements. Consequently, a respective confidence interval (noise level) is obtained for each level of signal. The technique is validated using test sets of biological images with known signal and noise characteristics. The method is also applied to assess uncertainty of measurement obtained with two CCD cameras in a wide‐field microscope.     

A procedure for minimizing cellular shrinkage in electron microscope preparation: a quantitative study on frog gall bladder

Nomarski differential interference contrast microscopy of whole-mount preparations of frog gall bladders has been used for light microscopic measurement of epithelial cell luminal area. Measurements were performed: in buffer after fixation, and in cured Epon after step-by-step and after continuous dehydration and infiltration procedures. Sections cut perpendicularly to the luminal surface were used for the measurement of epithelial cell height. From these measurements epithelial cell mean volumes were calculated. The comparative measurements showed that a step procedure results in significantly smaller cellular dimensions than does a procedure of slow and continuous change of concentration of the preparative media, the difference in epithelial cell mean volume being about 40%. Electron microscopy of thin sections of continuously processed specimens showed superior ultrastructural preservation of cytoplasmic density and microplical arrangement compared to the step processed counterparts. The principle was successfully applied in processing for scanning electron microscopy of osmotically extremely fragile preparations of erythrocyte ghosts; similarly, formation of the luminal cobblestone appearance of gall bladder epithelium was prevented. The present studies support the view that at least part of the volume shrinkage through the procedures of embedding is caused by osmotic gradients set up in the tissue.     

基于并行共聚焦显微系统的物方差动轴向测量

差动共聚焦显微成像技术可以获得很高的轴向测量精度,然而已有的差动共聚焦测量技术主要适用于激光扫描共聚焦,还不能满足微纳加工过程中对工件进行非接触式的在线、在位测量的要求。本文在分析差动共聚焦显微成像系统能够实现轴向测量原理的基础上,提出了适用于并行共聚焦技术的轴向测量方法。该方法利用均匀白光照明,在像方只需要使用一台相机做探测器,在物方通过移动载物台分别对样品在焦前和焦后两次成像,根据预先刻度好的差动曲线就可以得出物体表面的高度。理论模拟与实验结果均表明,该方法可以实现高精度的轴向测量,对500nm的台阶样品测量的平均误差为2.9nm,相对误差为0.58%。该方法简单、廉价、测量精度高,可以用于普通显微镜,易于实现样品的三维快速形貌还原与测量。     

An optical measurement of surface profile

With the recent advances in generating extremely smooth surfaces, new surface metrologies are needed to stay one step ahead. This paper describes a non-contact optical instrument for measuring surface profile with a height sensitivity of the order of 1 Å. The measurement technique, including pertinent design considerations, is outlined and measurements of polished and single point diamond machined surfaces are shown. The limitations as well as the potential impact of this technique are also discussed     

Comparison of optical and stylus methods for measurement of surface texture

Optical methods are increasingly used for measurement of surface texture, particularly for areal measurements where the optical methods are generally faster. A new Working Group under Technical Committee (TC) 213 in the International Organization for Standardization is addressing standardization issues for areal surface texture measurement and characterization and has formed a project team to address issues posed by the optical methods. In this paper, we review the different methods of measuring surface texture and describe a classification scheme for them. We highlight optical methods and describe some of their characteristics as well as compare surface-profiling results obtained from three optical methods with those obtained from stylus profiler instruments. For moderately rough surfaces (Ra?≈?500 nm), roughness measurements obtained with white light interferometric (WLI) microscopy, confocal microscopy, and the stylus method seem to provide close agreement on the same roughness samples. For surface roughness measurements in the 50 to 300 nm range of Ra, discrepancies between WLI and the stylus method are observed. In some cases the discrepancy is as large as about 75% of the value obtained with the stylus method. By contrast, the results for phase shifting interferometry over its expected range of application are in moderately good agreement with those of the stylus method.     

The light microscope on its way from an analytical to a preparative tool

Light intensities of up to 10¹³ W/cm² can be generated by focusing light, particularly laser pulses, into a microscope. Such power densities can be used to cut, perforate, or fuse microscopic objects with submicrometre accuracy. Suitable light sources for such a ‘microbeam’ are nitrogen lasers with a working wavelength of 337 nm, frequency-multiplied Neodym YAG lasers (266 or 355 nm) or excimer lasers (308 nm). In combination with dye lasers, tunable microbeams covering the wavelength range from the ultraviolet to the infra-red can be constructed. Such laser microbeams can be used to modify microchip substrates. Micro-injection of materials into biological cells or fusion of selected cell pairs under total microscopic control is also possible. Using the same equipment, elongated biological objects can be microdissected with submicrometre precision, for example in attempts to isolate DNA from a specific region of the human genome. In addition to the use of high-power pulsed lasers, the light of a continuous-wave infra-red laser can be used for the transport of microscopic objects. There, light pressure and the inhomogeneity of the electric field in a light pulse are used to trap microscopic objects in the focused laser beam, using the beam as ultrafine non-mechanical tweezers. Unlike mechanical microtools the optical trap is gentle and absolutely sterile. A combined laser microbeam and optical trap (a microbeam-trap) converts the light microscope, which is usually regarded as an analytical instrument, into a universal preparative instrument that allows micromanipulation of microscopic objects without mechanical contact. In contrast to any other micromanipulator, the microbeam-trap can work in the depth of an object without opening it.     

光学互相关测速系统设计与验证

针对两相流颗粒运动速度测量及基于互相关原理设计了双光路激光测速系统。采用搭建的变频电机带动绕丝产生已知旋转线速度的装置开展光学互相关测速验证实验。通过测量绕丝经双光路激光的光强衰减信号,再对两路信号进行互相关分析,从而得到测点绕丝旋转线速度。以电机转速计算的测点绕丝线速度作为参考值进行测量精度验证,得到光学互相关测速方法的测量相对误差在6%以内,验证了光学互相关测速方法的准确性。     

High speed nano-metrology

For manufacturing at the nanometre scale a method for rapid and accurate measurement of the resultant functional devices is required. Although atomic force microscopy (AFM) has the requisite spatial resolution, it is severely limited in scan speed, the resolution and repeatability of vertical and lateral measurements being degraded when speed is increased. Here we present a new approach to AFM that makes a direct and feedback-independent measurement of surface height using a laser interferometer focused onto the back of the AFM tip. Combining this direct height measurement with a passive, feedback-free method for maintaining tip-sample contact removes the constraint on scan speed that comes from the bandwidth of the z-feedback loop. Conventional laser reflection detection is used for feedback control, which now plays the role of minimising tip-sample forces, rather than producing the sample topography. Using the system in conjunction with a rapid scanner, true height images are obtained with areas up to (36 × 36) μm(2) at 1 image/second, suitable for in-line applications.     

Shearing interference microscope for step‐height measurements

A shearing interference microscope using a Savart prism as the shear plate is proposed for inspecting step‐heights. Where the light beam propagates through the Savart prism and microscopic system to illuminate the sample, it then turns back to re‐pass through the Savart prism and microscopic system to generate a shearing interference pattern on the camera. Two measurement modes, phase‐shifting and phase‐scanning, can be utilized to determine the depths of the step‐heights on the sample. The first mode, which employs a narrowband source, is based on the five‐step phase‐shifting algorithm and has a measurement range of a quarter‐wavelength. The second mode, which adopts a broadband source, is based on peak‐intensity identification technology and has a measurement range up to a few micrometres. This paper is to introduce the configuration and measurement theory of this microscope, perform a setup used to implement it, and present the experimental results from the uses of the setup. The results not only verify the validity but also confirm the high measurement repeatability of the proposed microscope.     

6 km自容式湍流观测剖面仪设计与试验研究

目前大部分湍流观测剖面仪的观测范围在1 km以浅。为获取深海湍流数据,探究深海动力过程演变机制与能量耗散过程,研制6 km自容式湍流观测剖面仪。从湍流观测应用的翼型剪切流传感器测量原理出发,分析约束深海剖面仪设计的关键技术,开展了深海剖面仪稳定水动力布局设计、耐压6 km的轻量化结构设计、下潜速度分析与控制设计。观测传感器集成微结构的双PNS系列翼型剪切流传感器与FP07快速温度传感器,实现了深海湍流两个维度下湍动能耗散与热耗散的同步、高速观测,采用模块化的设计思想完成自容式湍流观测硬件系统的设计。通过性能检测试验,剖面仪可满足6 km应用,下潜速度线性可调范围0.4~0.9 m/s,验证了剖面仪结构设计的可行性;海上试验,并与MSS90进行比测,剖面仪测量湍流脉动剪切变化趋势与MSS90相同,计算的湍流剪切波数谱与Nasmyth理论谱在截止波数前非常吻合,相同深度的湍动能耗散率与MSS90为同一数量级,验证了深海6 km自容式湍流观测剖面仪湍流测量的准确性。     

Two-photon image correlation spectroscopy and image cross-correlation spectroscopy

We introduce two-photon image correlation spectroscopy (ICS) using a video rate capable multiphoton microscope. We demonstrate how video rate two-photon microscopic imaging and image correlation analysis may be combined to measure molecular transport properties over ranges typical of biomolecules in membrane environments. Using two-photon ICS, we measured diffusion coefficients as large as 10⁻⁸ cm² s⁻¹ that matched theoretical predictions for samples of fluorescent microspheres suspended in aqueous sucrose solutions. We also show the sensitivity of the method for measuring microscopic flow using analogous test samples. We demonstrate explicitly the advantages of the image correlation approach for measurement of correlation functions with high signal-to-noise in relatively short time periods and discuss situations when these methods represent improvements over non-imaging fluorescence correlation spectroscopy. We present the first demonstration of two-photon image cross-correlation spectroscopy where we simultaneously excite (via two-photon absorption) non-identical fluorophores with a single pulsed laser. We also demonstrate cellular application of two-photon ICS for measurements of slow diffusion of green fluorescent protein/adhesion receptor constructs within the basal membrane of live CHO fibroblast cells.     

有图形硅片显微图像微距线宽测量方法研究

针对硅片关键尺寸高精度准确测量的要求，在整像素级标准件法二维图像微距尺寸测量的基础上，本文综合应用基于卡尺的标准件法和空间矩亚像素细分算法，提出了具有像素级高速度、亚像素级高精度线宽测量的两步标定法。通过给出一个焊盘样本的实际测量结果来分析对比，表明该方法测量精度有了明显地提高，可以用来进行有图形硅片关键尺寸的测量标定。