数字散斑干涉在振动测量中的应用

在动态测试领域中,数字散斑干涉技术常用到的相位处理方法有时问平均法和空间载波相移法.空间载波相移法因其简单性和实用性,被应用于双脉冲散斑干涉测量中.     

相移数字散斑干涉计量系统

本建立了一套相移激光数字散斑干涉自动测量系统,运用一系列的图象处理方法,实现了高精度的自动测量,显地提高了数字散斑干涉计量技术的可靠性、实用性及自动化程度。该计量系统被应用于变形、振动等参数的测量中,取得了较为理想的结果。     

Digital Double-pulsed Holographic Interferometry for Vibration Analysis

Abstract

In this paper we describe a digital double-pulsed holographic system. Two separate holograms of an object under test are recorded within a few microseconds using a charge-coupled device camera and stored in a frame grabber. The holograms are digitally reconstructed using a computer, by simulation of the Fresnel diffraction of the hologram illuminated by the reference wave. The phases of the two reconstructed wave fields are calculated from the complex amplitude and the deformation is obtained from the phase difference. Experimental results are presented.     

A Novel Technique for Spatial Phase-shifting Interferometry

Abstract

A novel technique for phase detection using three-step spatial phase-shifting interferometry is presented. The presented technique overcomes and studies the two main problems presented in the commonly used three-step phase-stepping technique. These problems deal with the leak of carrier frequency in the detected phase and the optimal carrier frequency to obtain the highest phase noise robustness.     

Noncontacting Measurement of Distortion by Digital Holographic Interferometry

Digital holographic interferometry is a coherent‐optical method for noncontacting measurement of full field deformations in the micrometer‐range. While deformations in the range of the wavelength of the used laser‐light are determined by comparison of the phases of the wave fields reconstructed from the recorded holograms, for larger deformations the form of the object surface has to be measured by a holographic interferometric contouring method, followed by numerical comparison of two such measured contours. Here we present such methods for determining the distortions of hot moving components leading to a concept for an in‐process distortion measurement enabling early interaction with e. g. the quenching process to control the resulting distortion.     

Low-Cost Non-Destructive Inspection by Simplified Digital Speckle Interferometry

The paper demonstrates a low-cost approach based on speckle interferometry (SI) for the nondestructive inspection (NDI) of metallic and composite plates. Speckle interferometry, and optical methods in general, provide a clear picture of the inspected area, where anomalies are immediately detected, and can yield results in real-time. They are often expensive though, and sensitive to environmental disturbances. Relevant literature in the area of nondestructive inspection is reviewed aiming to find the most suitable configuration for a low-cost system. The chosen setup is a simplified digital speckle interferometer (SDSI), which includes only three main components: a He-Ne laser, a standard CCD camera and a light-scattering window. This simplified configuration removes the requirement of mechanical stability by using a configuration close to the common-path interferometer. The SDSI device is here tested for the detection of thinning defects in Aluminum plates, and delamination in composite plates. Among the various stressing techniques, localized heating was found to be the simplest, yet most effective approach. Results show that the presence of defects creates unique features in the live correlation fringes, from which it is possible to identify the location and size of the defects. It is in conclusion demonstrated that the SDSI device is a valuable tool for fast, low-cost, and non-contact nondestructive inspection.     

基于EALCD的数字全息的研究

采用一种新的数字全息再现方法,将电荷耦合器件CCD与电寻址液晶EALCD相结合实现数字全息的再现.同时将数字图像处理技术与数字全息术相结合,应用MATLAB软件对记录的全息图进行数字图像处理,实验结果表明,该方法简单快速.通过图像增强等方法对全息图进行数字图像处理,在全息再现中,全息干涉图的对比度得到了显著的提高,有利于全息干涉条纹的自动判读.     

Three-dimensional Displacement Analysis by Windowed Phase-shifting Digital Holographic Interferometry

Abstract:  Phase-shifting digital holography is a new method for measuring the displacement distribution on the surface of an object. The authors previously proposed a windowed phase-shifting digital holographic interferometry (windowed PSDHI). This method provides accurate displacement distributions by decreasing the effect of speckle patterns. In this study, the method is extended to analyse three-dimensional displacement components in a microscope. Three object laser beams in the optical system are used. Four phase-shifted holograms are recorded for each object laser beam. The complex amplitude of each reconstructed light at the object is calculated by the Fresnel diffraction integral of the complex amplitude of the hologram. The reconstructed distance is obtained at the point with the maximum of the standard deviation of the intensities of the object reconstructed with changing the reconstruction distance. The three phase-difference values between before and after deformation provide the three-dimensional displacement components. Theoretical treatment and experimental results of three-dimensional displacement measurement using this method are shown.     

Holographic Interferometry Applied to the Comparative Measurement of Form and dimension of rolling bearing elements

An industrial application of the oblique illumination technique used for holographic interferometric comparison of non-optical surfaces is presented. A holographic interferometer for testing cylindrical and taper rollers is described. Experimental results are given, while it is discussed how to measure very small form deviations in spite of a decreased sensitivity of the interferometer due to the oblique illumination technique.     

激光数字波面干涉仪傅里叶变换移相干涉术

讨论了一种新的干涉图处理方法，能实时快速准确地提取干涉图信息，直接测量波面的位相分布，获得较高的位相分辨率和空间分辨率，使光学波面的检测精度达到λ／１００以上，并且实现了波面的的实时显示。     

数字中间片技术

数字中间片技术是国际上近几年发展起来并逐渐成熟的电影后期加工技术和方式。本文介绍了数字中间片的概念、优势、流程和应该注意的事项。     

数字技术给我国电影带来的变化和挑战

21世纪的今天数字技术已广泛应用于各行各业,给社会和人们的生活带来了巨大的变化。在电影领域里,数字技术从局部应用到系统应用、从试验到实践,目前电影正从传统的胶片方式向数字方式全面的过渡。这给电影带来了前所未有的变化和挑战,同时也带来难得的发展机遇。一、数字技术给电影带来的变化电影数字化是电影诞生百年以来最大的一次创新和变革。它使电影从艺术创作、拍摄制作和发行放映、市场运营到管理模式都发生了深刻的变化。中国的电影数字化应用始于90年代中期电影数字立体声的制作与放映。10年来特别是近几年在总局、电影局数字化发…     

误差分离技术在几何量测量中的应用

工件在检定过程中受到多种影响因素，其中仪器的影响占主要因素，为了提高测量精度，采用分离技术以消除仪器部分误差尤为重要。分离技术可用电算法和实用法，本文介绍其实用法。     

Carrier-modulated Object Step-loading Method of Automated Analysis in Digital Speckle Shearing Interferometry

Abstract

An object step-loading method has been recently reported to overcome the problems of phase unwrapping and decorrelation in digital speckle shearing interferometry. In this paper, a carrier modulation procedure is incorporated into the object step-loading method in order to improve the phase derivation accuracy. An added advantage with this approach is that the direction of deformation is also revealed.     

Axiomatic/Asymptotic Technique Applied to Refined Theories for Piezoelectric Plates

This article is devoted to the evaluation of refined theories for static response analysis of piezoelectric plate. The Carrera Unified Formulation (CUF) is employed to generate the refined plate models. The CUF allows the hierarchical implementation of refined models based on any-order expressions of the unknown variables. Equivalent single layer (ESL) and layerwise (LW) approaches are used to generate the refined models. The governing equations are obtained considering Navier-type, closed-form solutions. The axiomatic/asymptotic technique is employed in order to evaluate the relevance of each model term. This technique computes the relevance of a model term by measuring the error introduced with its deactivation with respect to a reference solution. The axiomatic/asymptotic technique is applied considering the sensor and actuator configurations for piezoelectric plates. Moreover, the analyses are performed taking into account the influence of the length-to-thickness ratio (a/h) and the use of isotropic or orthotropic materials. “Best” models are proposed and the stress/displacement components and electric potential distributions are evaluated by means of these reduced models.     

Critical Analysis of Dual-Probe Heat-Pulse Technique Applied to Measuring Thermal Diffusivity

The paper presents an analysis of the experimental parameters involved in application of the dual-probe heat pulse technique, followed by a critical review of methods for processing thermal response data (e.g., maximum detection and nonlinear least square regression) and the consequent obtainable uncertainty. Glycerol was selected as testing liquid, and its thermal diffusivity was evaluated over the temperature range from ??20 °C to 60 °C. In addition, Monte Carlo simulation was used to assess the uncertainty propagation for maximum detection. It was concluded that maximum detection approach to process thermal response data gives the closest results to the reference data inasmuch nonlinear regression results are affected by major uncertainties due to partial correlation between the evaluated parameters. Besides, the interpolation of temperature data with a polynomial to find the maximum leads to a systematic difference between measured and reference data, as put into evidence by the Monte Carlo simulations; through its correction, this systematic error can be reduced to a negligible value, about 0.8 %.     

Displacement Measurement Through Digital Image Correlation and Digital Speckle Pattern Interferometry Techniques in Cold‐Expanded Holes

Abstract: In this paper, the displacement field induced by the split‐sleeve cold expansion of holes was measured using both digital image correlation (DIC) and digital speckle pattern interferometry (DSPI) techniques. Thus, the experimental results, which were evaluated on the inlet surface of a 6082‐T6 aluminium plate, were compared with those from theoretical prediction. DIC provided accurate measurements up to the elastic–plastic boundary, whereas the DSPI technique highlighted the changes of displacement in the elastic domain. Prediction of the displacement based on the existing analytical model agreed with the experimental results achieved with both techniques. Possible explanations for the differences are discussed.