High precision phase measurement using reduced sine and cosinetables

A high-precision phase measurement technique, which can accurately determine the phase even when the signals are distorted by harmonics, was presented previously by the author (ibid., vol.38, p.954-60, Oct. 1989). He proposes a microprocessor-based hardware implementation of the technique. The hardware implementation requires two reduced tables: a sine table and a cosine table. If each table has i(i+5)/2 entries, then the phase can be accurately determined even if the signals are distorted by any number of harmonics in the range of second through ith harmonics     

Prospects for using combined-function sensors in precision displacement measurement

A survey is presented of prospects for using sensors that combine the functions of scanning, balancing, and interpolation. The survey covers the advantages and shortcomings of electromagnetic, piezoelectric, and magnetoelectric scanning and balancing interpolators. Translated from Izmeritel'naya Tekhnika, No. 1, pp. 19–22, January, 1999.     

Efficient estimation of extreme quantiles using adaptive kriging and importance sampling

This study considers an efficient method for the estimation of quantiles associated to very small levels of probability (up to O(10⁻⁹)), where the scalar performance function J is complex (eg, output of an expensive-to-run finite element model), under a probability measure that can be recast as a multivariate standard Gaussian law using an isoprobabilistic transformation. A surrogate-based approach (Gaussian Processes) combined with adaptive experimental designs allows to iteratively increase the accuracy of the surrogate while keeping the overall number of J evaluations low. Direct use of Monte-Carlo simulation even on the surrogate model being too expensive, the key idea consists in using an importance sampling method based on an isotropic-centered Gaussian with large standard deviation permitting a cheap estimation of small quantiles based on the surrogate model. Similar to AK-MCS as presented in the work of Schöbi et al., (2016), the surrogate is adaptively refined using a parallel infill criterion of an algorithm suitable for very small failure probability estimation. Additionally, a multi-quantile selection approach is developed, allowing to further exploit high-performance computing architectures. We illustrate the performances of the proposed method on several two to eight-dimensional cases. Accurate results are obtained with less than 100 evaluations of J on the considered benchmark cases.     

自适应窗口傅里叶变换三维面形检测技术

通过小波脊变换,得到局部条纹的最佳变换窗口,在傅里叶变换三维测量时,可以保证窗口尺寸随变形条纹频率变化而自动调整。实验研究表明,此方法克服了窗口傅里叶变换空间．频率分辨率无法调整的问题,可以最大限度地抑制变形条纹的频谱混叠,准确地提取基频信息,大大地提高了测量精度,误差范围由-2～8mm降低为-1～1mm。并且,由于只需要从一帧条纹图中获取物体的三维分布,适合于动态测量。     

An adaptive sampling method for variable-fidelity surrogate models using improved hierarchical kriging

Variable-fidelity (VF) modelling methods have been widely used in complex engineering system design to mitigate the computational burden. Building a VF model generally includes two parts: design of experiments and metamodel construction. In this article, an adaptive sampling method based on improved hierarchical kriging (ASM-IHK) is proposed to refine the improved VF model. First, an improved hierarchical kriging model is developed as the metamodel, in which the low-fidelity model is varied through a polynomial response surface function to capture the characteristics of a high-fidelity model. Secondly, to reduce local approximation errors, an active learning strategy based on a sequential sampling method is introduced to make full use of the already required information on the current sampling points and to guide the sampling process of the high-fidelity model. Finally, two numerical examples and the modelling of the aerodynamic coefficient for an aircraft are provided to demonstrate the approximation capability of the proposed approach, as well as three other metamodelling methods and two sequential sampling methods. The results show that ASM-IHK provides a more accurate metamodel at the same simulation cost, which is very important in metamodel-based engineering design problems.     

Method for the measurement of phase retardation of any wave plate with high precision

We present a measuring method for any wave plate retardation with fairly high precision that utilizes a laser frequency splitting technique. To avoid strong mode competition in measuring half and full wave plates, we use two separate methods: comparing adjacent longitudinal mode spacing, and phase offset with an additional quarter wave plate. Therefore any wave plate can be characterized by a single instrument, and no complicated experimental arrangement or data analysis is required. The performance of the system is demonstrated by determining the phase retardation of several samples to a precision and repeatability better than lambda/10(4); moreover, an error analysis is proposed.     

High precision measurement of the topological Aharonov–Casher effect with neutrons

The phase shift predicted by Aharonov and Casher (AC) for a magnetic dipole diffracting around a line charge was first observed by Cimmino et al. using a neutron interferometer. A number of subsequent atom interferometry experiments have been performed to observe this effect. These experiments measured the v×E phase shift due to the magnetic field induced in the rest frame of the atom, with no indication of the topological nature of the AC interaction. We intend to perform a high precision AC experiment with neutrons to improve the accuracy of our previous results and to highlight the topological nature of the effect. Finally, we present a novel geometry to achieve a spin-dependent magnetic phase shift.     

Large in-plane displacement measurement in dual-beam speckle interferometry using temporal phase measurement

Abstract

Measurement of in-plane displacements of a diffuse object by observing the temporal fluctuation of the speckle pattern in a dual-beam illumination speckle interferometer is illustrated. To conceive the temporal changes the object is displaced in its plane continuously. A high-speed camera is used to acquire a number of frames of the image of the object motion sequentially. Through Fourier transformation and inverse Fourier transformation of the frames stacked together, the total phase is determined. Finally, the magnitude of the in-plane displacement of the object motion is extracted. The range of displacement that can be measured using this novel method lies between few microns and over 100 μm on the upper end. Theory together with experimental results are presented in this paper.     

A precision measurement strobe converter

The basis of a method of correcting the structure of a precision measurement strobe converter with feedback, in which, to minimize the total conversion error, the parameters of the strobe pulses are adjusted, is presented. The converter is designed to transform the time scale of wide-band periodic signals, about the frequency and amplitude of which preliminary data are available. In the absence of a priori data, measurement of the signal parameters is performed in stages.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 48–50, September, 1993.     

Investigation of an adaptive sampling method for data interpolation using radial basis functions

An adaptive sampling method is presented for optimizing the location of data points in parameter space for multidimensional data interpolation. The method requires a small number of points to begin, and achieves a compromise between space‐filling updates and local refinement in areas where the data are nonlinear, as measured by the Laplacian. A smooth separation function quantifies the sample spacing, and this is blended with the Laplacian to form a criterion on which to assess potential new sample positions. Validation results are presented using two‐dimensional analytic test cases, which demonstrate that the method can recover known optimal designs and gives improvement over data‐independent approaches. In addition, a detailed analysis of the various model parameters is presented. Initial findings are very promising, and it is hoped that further work using the method to generate an aerodynamic database using CFD simulations will lead to a reduction in the number of points required for a given modelling accuracy. Copyright © 2010 John Wiley & Sons, Ltd.     

Path difference measurement using phase stepping with white light

Phase stepping algorithms are commonly used with narrow bandwidth sources for fast accurate measurement of interferometer phase differences. We show that path difference can also be measured using phase stepping with a wide bandwidth source. The errors resulting from the spectral characteristics of the source are discussed and shown to be relatively small, allowing measurement of path difference to typically 0.1 μm or better. White-light phase stepping is demonstrated experimentally with results which closely match those predicted theoretically.     

Flexible sampling frame measurement system

The self-programmable system to decrease semantic redundancy is analyzed. Equations are found for the changing threshold value and the channel capacity for the source flexible sampling program. The software packets system realization was prepared, and the operating simulation was performed