Numerical analysis of fringe patterns recorded in holographic interferometry using high-order ambiguity function

This letter introduces a new approach for the demodulation of fringe patterns recorded in holographic interferometry using high-order ambiguity function (HAF). The proposed approach is capable of retrieving the phase from a single fringe pattern. The main advantage of this approach is that it directly provides an estimation of the continuous phase distribution and thereby avoids the necessity of using a cumbersome 2D phase unwrapping procedure. This method first computes the discrete-time analytic signal of the recorded fringe pattern. Then, by modelling this analytic signal as a polynomial phase signal embedded in additive complex white Gaussian noise, a parametric estimation procedure based on HAF is employed to directly estimate the unwrapped phase distribution. Numerical simulations and experimental results demonstrate the potential of the proposed approach.     

Wavefront watermarking of technical and biological samples using digital random phase modulation and phase retrieval

A technique for digital watermarking of smooth object wavefronts using digital random phase modulation and multiple-plane iterative phase retrieval is demonstrated experimentally. A complex-valued watermark is first encrypted using two random phase masks of known distributions before being superposed onto a set of host wavefront intensity patterns. Encryption scaling factor and depth of randomization of the masks are optimized such that the amplitude and phase watermarks are decrypted successfully and are not distorting the host wavefront. Given that the watermarked intensity patterns and the numerous decryption keys are available (i.e. distances between recording planes, light source wavelength, pixel size, random phase masks and their distances to the planes are all known), increasing the number of watermarked patterns used results in enhanced quality of decrypted watermarks. The main advantage of wavefront watermarking via the phase retrieval approach compared to the holographic approach is the avoidance of reference wave-induced aberration. Watermarking of wavefronts from lenses and unstained human cheek cells demonstrate the effectiveness of the technique.     

Recovery of absolute phases for the fringe patterns of three selected wavelengths with improved anti-error capability

Abstract

In a recent published work, we proposed a technique to recover the absolute phase maps of fringe patterns with two selected fringe wavelengths. To achieve higher anti-error capability, the proposed method requires employing the fringe patterns with longer wavelengths; however, longer wavelength may lead to the degradation of the signal-to-noise ratio (SNR) in the surface measurement. In this paper, we propose a new approach to unwrap the phase maps from their wrapped versions based on the use of fringes with three different wavelengths which is characterized by improved anti-error capability and SNR. Therefore, while the previous method works on the two-phase maps obtained from six-step phase-shifting profilometry (PSP) (thus 12 fringe patterns are needed), the proposed technique performs very well on three-phase maps from three steps PSP, requiring only nine fringe patterns and hence more efficient. Moreover, the advantages of the two-wavelength method in simple implementation and flexibility in the use of fringe patterns are also reserved. Theoretical analysis and experiment results are presented to confirm the effectiveness of the proposed method.     

采用双DSP的实时傅里叶变换系统设计

系统设计目的是使FFT变换能够实时完成,以便能够在图像处理等方面应用于实际工程中。系统应用两片TI公司的数字信号处理器TMS320C6416为核心,以可编程逻辑阵列CPLD进行逻辑控制,采用两片现场可编程门阵列FPGA分别作为图像预处理和两片DSP之间的通讯,系统在运算1024点FFT与反傅里叶变换iFFT时耗仅为178μs,实现了实时的图像傅里叶处理。     

Study of adaptive elliptical ideal low-pass filters used for denoising of digital speckle interferograms obtained in phase-shifting digital speckle pattern interferometry

Ideal low-pass filtering methods were studied in detail and adaptive elliptical ideal low-pass filters proposed for the first time. The proposed adaptive elliptical ideal low-pass filters can be used effectively for denoising of digital speckle interferograms obtained in phase-shifting digital speckle pattern interferometry. The shape of adaptive elliptical ideal low-pass filters is determined according to the spectrum distribution of interference fringes by using the adaptive method. Theoretical analysis, simulation calculation, and experimental results are presented, and are in good agreement.     

基于EMD算法的光栅莫尔条纹信号去噪方法研究

针对计量光栅莫尔条纹信号的质量问题,提出了基于经验模态分解（EMD）算法对非平稳光栅莫尔条纹信号模型的去噪方法。建立非平稳的光栅时变信号模型,利用EMD算法不需要定义滤波器参数的自适应性优点,对添加不同噪声的多组光栅信号模型进行了滤波分析的仿真实验,其信噪比和均方根误差两项指标优于均值滤波、小波阈值去噪方法。对两路正余弦理想信号添加高次谐波分量,通过对比EMD算法抑制高次谐波前后的李萨如图形,验证了该方法在去噪过程中对光栅莫尔条纹信号正弦性误差补偿的良好效果。     

Error analysis in the absolute phase maps recovered by fringe patterns with three different wavelengths

In a recently published work, we proposed a technique to recover the absolute phase maps from the wrapped ones with three different fringe wavelengths. It was noticed that when the wrapped phase maps are obtained by three-step phase shifting method, errors in fringe order still occur, leading to significant error in the recovered absolute phase maps. In this paper, the characteristic and reason of the errors are analysed, and a method to avoid these errors is also proposed. The theoretical conclusions in this paper are validated with experimental results.     

Convergence and bias in the LSG algorithm for adaptive lattice filters

The lattice filter has several desirable characteristics that make it attractive in adaptive applications. The Lattice Stochastic Gradient (also called Gradient Adaptive Lattice algorithm) is popularly used to adapt the lattice filter. However, a theoretical study of the bias in the reflection coefficient and the convergence of the LSG algorithm have not been studied extensively yet. This paper presents some theoretical results on these issues. It is hoped that the results will also present some insights into the factors affecting the convergence of the filter.     

炉温均匀性测试数据处理系统的设计与实现

在航空工业中,对炉温的均匀性要求比较高。文章所设计的数据处理系统作为炉／槽温度均匀性测试装置的软件部分,实现了对测量数据的自动修改、过滤及参数计算等功能。该系统实现中用到了PB与Excel的数据通信等关键技术。本系统已应用在西飞的军民机生产、转包生产、民品生产等项目中。     

基于LabVIEW的颤振激励信号生成与测试系统研究

基于NI公司的数据采集硬件设备,结合跨音速风洞颤振试验特点,用LabVIEW语言为颧振试验设计了一套激励信号生成与多通道同步动态信号采集系统.设计的系统成功实现了新型IEPE传感器和传统电荷式传感器兼容、加速度信号与应变信号同步采集、激励信号生成与多通道数据采集同步、直接内存读取数据、数据尤限时存盘、信号实时显示等方面的功能.经试验验证,该系统设计方案完全满足颤振试验数据采集的要求,获得良好的测试结果,在多功能同步采集系统设计方丽取得了技术性应用成果.     

汽车中力信号测试系统的设计

我国正处于汽车高速发展阶段，高性能汽车的急剧增长速度与相应的使用维护水平存在着明显的差距，使用维护水平的提高，必须依赖对汽车现代检测、诊断仪器的开发和运用，因此开展对汽车相关测试系统的研究非常必要。力信号测试是汽车测试中重要的组成部分，在介绍了检测系统的原理与组成基础上，本文设计了一套基于VB的汽车中力信号测试系统，实现了对力信号的实时检测与分析处理。系统调试结果表明，该测试系统达到了设计要求。实践证明，基于VB的汽车中力信号测试系统界面直观，便于操作，取得了很好的教学效果。     

提高扭转振动瞬态信号处理精度的方法研究

用测试扭振信号来分析轴系的各谐次幅值特性,研究扭转共振是解决由扭振产生故障问题的有效方法之一。针对发动机升降速过程扭振信号是瞬态时变信号,并存在低频滚振干扰,不能采用转速跟踪分析方法直接进行分析的特点,提出了将一次采样样本所包含的整周期数扩大一倍,加Ｈａｎｎｉｎｇ窗进行转速跟踪分析的方法,消除了低频滚振的影响,大大提高了升降速过程扭振各谐次幅值分析精度。这种方法既能在试验台上测试分析发动机的扭振特     

自相关域信号相位匹配原理的正弦信号参数估计

对单路接收信号的自相关函数使用等间隔或变间隔时延截取得到M段信号,进而采用相位匹配原理进行正弦信号参数估计,能够进一步改善估计性能,尤其是变间隔时延可抑制大部分奇异峰。仿真结果表明,自相关域信号相位匹配原理的正弦信号参数估计精度优于频域信号相位匹配原理的参数估计精度。     

飞机气压关断活门计算机辅助测试系统的设计

针对军用飞机修理厂对飞机高温高压大流量气压调节关断活门修理后的测试难的问题,设计制造了以计算机为核心的“飞机气压关断活门计算机复制测试系统”。本文介绍了该系统的基本组成、工作和技术特点。     

Analysis of the improvement in sky coverage for multiconjugate adaptive optics systems obtained using minimum variance split tomography

The scientific utility of laser-guide-star-based multiconjugate adaptive optics systems depends upon high sky coverage. Previously we reported a high-fidelity sky coverage analysis of an ad hoc split tomography control algorithm and a postprocessing simulation technique. In this paper, we present the performance of a newer minimum variance split tomography algorithm, and we show that it brings a median improvement at zenith of 21 nm rms optical path difference error over the ad hoc split tomography control algorithm for our system, the Narrow Field Infrared Adaptive Optics System for the Thirty Meter Telescope. In order to make the comparison, we also validated our previously developed sky coverage postprocessing software using an integrated simulation of both high- (laser guide star) and low-order (natural guide star) loops. A new term in the noise model is also identified that improves the performance of both algorithms by more properly regularizing the reconstructor.     

串联式制动阀静特性仿真及测试方法研究

针对串联式制动阀结构特征及静特性工作机理,基于AMEsim建立参数模型,分析结构参数对其性能影响;以行业标准为依据,结合工作机理及仿真参数,优化测试方法,设计线性模拟负载机构真实复现实车制动状态下静特性响应流程;结合高精度数据采集系统,以LabVIEW为平台开发测试软件,研制了一套静特性测试系统。对比分析仿真结果与实测数据,引入测试系统分析(MSA)方法,验证模型与系统的可靠性。实验数据表明:研制的测试系统测量能力指数Cg大于1.67,系统精确度指标均小于30%,符合新设备验收及静特性测试要求。     

用灰度曝光技术改善数字光刻图形轮廓

基于空间光调制器(SLM)数字光刻技术可用于IC掩模制作或直接作为微结构的加工工具,但用数字投影光刻系统加工某些结构的二元图形时,往往难以获得预期的图形轮廓,即图形边缘处有一定畸变,特别是较低缩小倍率时。本文提出优化设计图形边缘灰度的方法来校正光刻图形的畸变。文中分析了数字光刻制作这些二元光刻图形时空间像畸变产生的物理机制,详细讨论了设计图形边缘灰度优化的规则,并以加工圆孔滤波器为例,模拟了它的数字光刻成像过程。结果表明,设计图形的边缘采用灰度曝光可使其空间像畸变减小约8个百分点,光场分布更为均匀。数字灰度曝光技术简单易行,可为改善光刻图形质量提供了新途径。     

New methods and technologies for the identification of optical measurements performed by video cameras with degeneration in the arrangement of test objects in the plane

New methods and technologies for the identification of optical measurements for video cameras in cases where the spatial arrangement of the test objects (test objects) in the plane becomes degenerate are considered. Moscow, Russia. Translated from Izmeritel’naya Tekhnika, No. 5, pp. 23–29, May, 2008.     

变速机械弱时变信号幅值谱校正的多点平均法

系统而完整地提高了处理变速机械弱时变响应信号的离散频谱多点平均幅值修正法的理论和方法,严格证明了该方法能精确地计算出平稳信号和频率微弱波动信号的幅值,能近似地计算出幅值和频率均微弱波动的信号的平均幅值,并应用这套理论成功地解释了频率微弱波动信号的幅值谱表现出较严重的“动率泄露”效应的原因。     

管片拼装试验台回转电液控制系统设计及试验分析

 针对管片拼装机高速、高精度及低冲击自动拼装技术的需求,在全面分析了管片拼装机回转驱动系统大行程、大惯量及长时间运行特点的基础上,设计了以比例换向阀为调节核心、以平衡阀为辅助保障的管片拼装试验台回转电液控制系统.参考工程应用管片拼装机相关参数及管片拼装试验台设计要求,基于相似理论提出拼装试验台回转电液控制系统参数指标及原理图,运用SolidWorks建模仿真及负载力矩分析,进而完成电液控制系统参数设计及元件选型,最后完成了¢2 m管片拼装试验台回转电液控制系统的搭建及试验分析工作.试验分析结果表明：系统稳态性能满足设计要求,最大转速为6.25 r/min;同时具有良好的动态性能,系统阶跃响应峰值时间为1.1 s,可平稳实现斜坡减速及低速停车．