Recognition and classification of red blood cells using digital holographic microscopy and data clustering with discriminant analysis

We propose to apply statistical clustering algorithms on a three-dimensional profile of red blood cells (RBCs) obtained through digital holographic microscopy (DHM). We show that two classes of RBCs stored for 14 and 38 days can be effectively classified. Two-dimensional intensity images of these cells are virtually the same. DHM allows for measurement of the RBCs' biconcave profile, resulting in a discriminative dataset. Two statistical clustering algorithms are compared. A model-based clustering approach classifies the pixels of an RBC and recognizes the RBC as either new or old based. The K-means algorithm is applied to the four-dimensional feature vector extracted from the RBC profile.     

Microgravity materials and life sciences research applications of digital holography

We investigate the utility of digital holographic interferometry for analyzing gravity-dependent mass transport phenomena as applicable to materials and life science research topics. Digital holography is useful for measurement of parameters that introduce phase changes in light traversing the material of interest, such as temperature or concentration variations in an aqueous environment. We have constructed, tested, and verified a compact, portable digital holographic monitor (DHM) suitable for characterization of transparent samples. It has proved useful for the study of systems such as protein crystal growth solutions and has been proposed for further application into studies involving microbial metabolism. The DHM is also sufficiently rugged for field operation in challenging environments a s may be encountered in a spacecraft or industrial setting. We discuss some system capabilities and limitations.     

Parallel two-step phase-shifting digital holograph microscopy based on a grating pair

An optical configuration for parallel two-step phase-shifting digital holographic microscopy (DHM) based on a grating pair is proposed for the purpose of real-time phase microscopy. Orthogonally circularly polarized object and reference waves are diffracted twice by a pair of gratings, and two parallel copies for each beams come into being. Combined with polarization elements, parallel two-step phase-shifting holograms are obtained. Based on the proposed configuration, two schemes of DHM, i.e., slightly off-axis and on-axis DHM, have been implemented. The slightly off-axis DHM suppresses the dc term by subtracting the two phase-shifting holograms from each other, thus the requirement on the off-axis angle and sampling power of the CCD camera is reduced greatly. The on-axis DHM has the least requirement on the resolving power of the CCD camera, while it requires that the reference wave is premeasured and its intensity is no less than 2 times the maximal intensity of the object wave.     

Effects of birefringence on Fizeau interferometry that uses a polarization phase-shifting technique

Interferometers that use different states of polarization for the reference and the test beams can modulate the relative phase shift by using polarization optics in the imaging system. Thus the interferometer can capture simultaneous images that have a fixed phase shift, which can be used for phase-shifting interferometry. As all measurements are made simultaneously, the interferometer is not sensitive to vibration. Fizeau interferometers of this type have an advantage compared with Twyman-Green-type systems because they are common-path interferometers. However, a polarization Fizeau interferometer is not strictly common path when both wavefronts are transmitted by an optic that suffers from birefringence. The two polarized beams see different phases owing to birefringence; as a result, an error can be introduced in the measurement. We study the effect of birefringence on measurement accuracy when different polarization techniques are used in Fizeau interferometers. We demonstrate that measurement error is reduced dramatically and can be eliminated if the reference and test beams are circularly polarized rather than linearly polarized.     

Vibration-resistant direct-phase-detecting optical interferometers

Two dual-beam differential direct-phase-detecting optical interferometers for scanning moving surfaces are described. Two beams from these interferometers are focused ~42 mum apart on moving surfaces, and the difference in their reflected path lengths is measured to provide the surface roughness measurement. These interferometers are exceptionally insensitive to environmental vibrations and to surface physical and chemical factors. Applications discussed include the measurement of the surface roughness of a rotating cylinder and a moving web.     

平衡式干涉仪的光学系统设计

介绍了两种平衡式干涉仪的光学系统设计方法,分别给出了用于单端测量和双端测量的具体设计方案.由于采用的平衡式光学系统中测量光束和参考光束具有近似相等的光程长度和相似的路径,其光程差仅由被测件的长度或被测表面与测量参考镜之间的距离而引起,因此干涉仪具有很高的稳定性.用双端测量双光程平衡式干涉仪对准零长度试样进行测量,在185 h测量中所得数据的标准偏差为2.1 nm.     

大长度激光测量中阿贝误差消除方法的研究

提出一种基于3路独立激光干涉仪消除大长度激光测量中的阿贝误差的方法,3路干涉仪的安装位置可布置成任意三角形。通过3路干涉仪的测量结果及被测仪器与3路干涉仪安装位置的几何关系,构造一路与被测仪器同光路的虚拟干涉仪,推导虚拟干涉仪的测长公式。该算法对干涉仪的安装位置无特殊要求,在实践中易于实现。为验证算法的有效性,依托于室内80 m大长度标准装置,通过改变被测仪器安装位置,在45 m范围内进行了3组不同的验证实验。实验结果显示消除阿贝误差后,残余的其它误差的最大值仅为1.10 μm,该算法可有效地消除阿贝误差。     

Design and performance of cryogenic, scanning Fabry-Perot interferometers for the Long-Wavelength Spectrometer on the Infrared Space Observatory

The design of cryogenic, scanning Fabry-Perot interferometers for the Long-Wavelength Spectrometer on the ESA Infrared Space Observatory is presented. The interferometers were designed to provide a spectral resolving power of 10(4) over the wavelength range 45-180 μm, with the highest possible transmission efficiency consistent with this requirement. Metal meshes, custom designed with the aid of a theoretical model of metallic reflection, were used as the reflecting elements. The scanning mechanism featured a spring-suspended plate, which was servocontrolled by moving coil actuators and monitored by capacitance micrometers. The spectroscopic performance of the interferometers was measured in the laboratory and is compared with the model developed for the interferometer design. Although the measured resolving powers were somewhat lower than expected because of the laboratory measurement conditions, the transmission efficiencies were in approximate agreement with the design specification.     

Multiple access coding interferometers in wave radio

Wave radios in the past have used passive wide-band with no multiple access (MA) coded interferometer architectures in modulator and demodulator circuits for QPSK digital data transmission and reception. The authors provide information and design insight on the use of MA coded interferometers in modulator and demodulator for UWB wave radio. Wave radio fitted with hardware MA coded interferometers offers MA to users as does CDMA using data codes. Experimental and simulation analyses of coded interferometers show that it is possible to establish a one-to-one wave radio hardware link by means of hardware-based codes (addresses). The number of UWB hardware-coded interferometers investigated is limited to three codes (code 0, code 1 and code 2) for demonstration purposes only.     

Prism-pair interferometry by homodyne interferometers with a common light source for high-accuracy measurement of the absolute refractive index of glasses

A prism-pair interferometer comprising two homodyne interferometers with a common light source was developed for high-precision measurements of the refractive index of optical glasses with an uncertainty of the order of 10(-6). The two interferometers measure changes in the optical path length in the glass sample and in air, respectively. Uncertainties in the absolute wavelength of the common light source are cancelled out by calculating a ratio between the results from the interferometers. Uncertainties in phase measurement are suppressed by a quadrature detection system. The combined standard uncertainty of the developed system is evaluated as 1.1×10(-6).     

A prototype optical encoder system with nanometer measurement capability

Optical gratings are becoming available with precision down to the 2 nm level, or below. Such gratings can be employed to make highly accurate measuring tools such as optical encoders and coordinate measuring tools which can find numerous applications in precision machining applications and integrated circuit industry such as image placement inspection. Such tools are significantly less expensive than interferometers because of the relaxed mechanical tolerances required on the associated stages. In this paper, a novel prototype optical encoder system is developed for grating-based measurement tools with nanometer accuracy. The location of the grating was determined with an error of 0.09 nm. This is comparable to the accuracy of state-of-the-art interferometers, but at much lower cost.     

Computerization of white-light contact interferometers based on optical image processing

A technique of computerization of white-light contact interferometers intended for calibration of reference end gauges and other objects in the range 0.1–1000 mm with resolution 0.001 μm is considered. Results are presented from studies of contact interferometers based on digital processing of interference images with the use of corresponding mathematical software. __________ Translated from Izmeritel’naya Tekhnika, No. 7, pp. 35–38, July, 2006.     

Measurement by multidirectional interferometers of the position and orientation of a positioning stage

A multidirectional interferometer system is developed to determine the position and orientation of a stage moved in a two-dimensional (2-D) space. In this system four corner-cube prisms are mounted on the moving stage, and four laser beams are incident on the corner cubes in different directions. Moving distances in the observed directions are measured by laser interferometers. The position and orientation of the stage are calculated from the moving distances of the corner cubes. Some experiments are done on the 2-D moving stage with four interferometers, and measurement errors are estimated from redundant data. The estimated accuracy is higher than 0.2 microm for translation and 0.3 x 10(-3) deg for rotation for a measurement range of 0.5 mm and 0.5 deg.     

Enlarging the angle of view in Michelson-interferometer-based shearography by embedding a 4f system

Digital shearography based on Michelson interferometers suffers from the disadvantage of a small angle of view due to the structure. We demonstrate a novel digital shearography system with a large angle of view. In the optical arrangement, the imaging lens is in front of the Michelson interferometer rather than behind it as in traditional digital shearography. Thus, the angle of view is no longer limited by the Michelson interferometer. The images transmitting between the separate lens and camera are accomplished by a 4f system in the new style of shearography. The influences of the 4f system on shearography are also discussed.     

Estimation of phase shifts linked only to the coating for a dielectric mirror

The wavefront is an important characteristic for a dielectric mirror. Its measurement is usually performed with interferometers. We introduce a new method to evaluate only the coating wavefront distortion due to nonuniform thickness errors by using a reflectometer. This method uses some reflectance or transmittance maps at a wavenumber σ(m) for which the reflectance or transmittance factor variation is high. These variations are translated into some central wavenumber σ(c) variations, which enables the determination of a phase map from experimental treatment.     

A viscous-type dynamic hysteresis model as a tool for loss separation in conducting ferromagnetic laminations

A viscous-type dynamic hysteresis model (DHM) that is compatible with any static hysteresis model is described. In contrast to existing dynamic models, the DHM is characterized by fixed desired properties over an infinite frequency range and provides the possibility of changing the shape of the steady-state hysteresis loop. The way the DHM is combined with Maxwell equations makes it possible for the first time to separate all three components of the total loss in conducting ferromagnetic laminations. These are the static hysteresis loss, classical eddy-current loss, and the excess loss treated as a dynamic hysteresis component. The study of their frequency dependencies opens a possibility of accurate iron loss prediction based on the loss separation principle.     

激光干涉仪在纳米测量中的典型应用

激光干涉仪具有测量分辨力高、测量结果可溯源等优点,在纳米测量中的应用日益广泛。介绍纳米测量机和低膨胀材料线膨胀系数测量装置中应用的迈克尔逊型激光干涉仪以及在高准确度位移测量装置中应用的法布里-珀罗型激光干涉仪,并结合这些实例对激光干涉仪光学系统设计、测量环境控制、迈克尔逊干涉仪非线性误差补偿以及法布里-珀罗干涉仪量程扩展等方面的关键问题进行分析和总结。所述原则和方法对实现纳米级测量准确度具有重要意义,可为高准确度激光干涉仪的研制及其在纳米测量中的更广泛应用提供技术参考。     

Motion generation and virtual simulation in a digital environment

The growing complexity in product design and manufacturing processes has made virtual prototyping an important new approach that enhances products and process development. Considering the ergonomic issues evident in product lifecycles, digital human modelling (DHM) is adopted for virtual simulation and proactive evaluation. A motion generation from semantics (MGS) system is proposed in this research. The MGS system features include virtual prototyping, natural language instruction, a method time measurement (MTM) translator and motion generator. The system was implemented using product lifecycle management (PLM) software and validated in an automotive manufacturing company. The practice of intuitively generating manual operations and conducting virtual simulations enables the system planners to quickly respond to manufacturing process changes and recursively improve the tooling and process design flexibility and efficiency.     

Differential interferometry in heat transfer

In this paper the optical methods in heat transfer applications are described briefly. In particular, interferometric methods are discussed in detail as applied to the study of natural convection heat transfer. Of the most popular interferometers, viz. the Mach Zehnder Interferometer (mzi) and the Differential Interferometer (di), thedi is considered in detail. The theoretical and constructional features of adi are outlined. The procedures of heat transfer measurement and the temperature profile estimation are explained. The advantages and limitations of the two interferometers are compared with the help of a sample calculation. The experimental analyses of three cases, viz. (1) isothermal vertical flat plate, (2) single vertical fin attached to a heated horizontal base, and (3) horizontal fin array, are described. Typical heat transfer and temperature profile results are presented. Using the estimated temperature profiles isotherms are plotted. It is possible to get fairly good heat transfer and temperature profiles using adi. The instrument is specially useful in applications involving short optical path lengths because of its superior resolution as compared tomzi.     

多边法位姿测量系统中跟踪方式对测量精度的影响研究

为了精确测量大尺寸位姿,建立了一种由7台激光跟踪干涉仪组成的大尺寸位姿测量装置。根据测量各反射镜的激光跟踪干涉仪数量的不同,采用322和331两种跟踪方式对位姿测量精度的影响进行仿真实验,从而发现被测点位置与基站构成平面的距离相关,由坐标解算公式推导被测点坐标值与测量基站之间的相对位置与测量误差间的误差模型,通过分析x、y、z 方向上误差对距离变化的敏感程度,发现z方向距离变化引起的误差最为敏感。当被测点与测量基站的距离由1300.8mm减小到0mm时,测量误差由2.2μm增大到2626.1μm。实际姿态测量结果表明:当采用一种跟踪方式时可以避免被测点与测站点平面过近,有利于提高系统测量精度,所提出的误差模型可为多边法位姿测量系统的优化布局提供一种量化的理论分析方法。