数据采集系统通道采集速率的精确评价方法

目的 介绍数据采集系统采集速率的一种简单实用的精确评价方法，即正弦波拟合评价法。方法 核心技术除了采用最小二乘波形拟合手段外，还采用了一种性能特性的单频数字滤波器技术，该滤波器仅对噪声和谐波有滤除作用，从原理上说，对于正弦信号的幅度、相位、频率和直流分量４个参数均无影响，讨论了评价过程的误差来源，以及上其评价误差的几种对策；并阐述了小菠 方法及过程，同时，以滤波前后效果对比的方式给出了评价过程的计     

数据采集系统通道采集速率的精确评价方法

目的　介绍数据采集系统采集速率的一种简单实用的精确评价方法 ,即正弦波拟合评价法 .方法　核心技术除了采用最小二乘波形拟合手段外 ,还采用了一种性能独特的单频数字滤波器技术 ,该滤波器仅对噪声和谐波有滤除作用 ,从原理上说 ,对于正弦信号的幅度、相位、频率和直流分量 4个参数均无影响 .讨论了评价过程的误差来源 ,以及减小其评价误差的几种对策 ;并阐述了滤波方法及过程 ,同时 ,以滤波前后效果对比的方式给出了评价过程的计算机仿真结果 .结果　使用该方法评价采集速率 ,结果不确定度可达到 1 0 - 6量级 ,加上数字滤波器后 ,不确定度可降低一半以上 .结论　所述方法可以用于采集速率的精确评价     

正弦信号源波形失真的一种精确评价方法

叙述了正弦信号源失真的分类 :谐波失真、噪声失真和杂波失真 ;讨论了失真测量的基本技术 (模拟法和FFT法 )的优点和局限性 ,分析了失真测量技术的难点和技术状况 ;介绍了谐波失真和总失真度的定义。提出了使用正弦波曲线拟合法评价正弦波信号源总失真度的过程 ,在能量守衡以及失真和信号本身不相关的前提下 ,详细分析和推导了量化误差对失真度评价的影响及修正公式 ,实现了正弦波信号源总失真度的精确评价 ,实验结果验证了该方法的正确性及切实可行性。同时 ,对评价方法进行了误差分析 ,该方法可用于正弦信号波形失真度的精确测量和计量校准     

用正弦波拟合法评价数据采集系统的通道间延时

本文介绍了数据采集系统通道间延时的一种简单实用的评价方法,讨论了评价过程的误差来源,以及减小其评价误差的几种对策;同时,给出了评价过程的计算机仿真结果。     

通道间延迟时间差的测量不确定度

介绍了用正弦波拟合法评价测量系统通道间延迟时间差不确定度的分析和评定过程。讨论了几个主要的不确定度来源,包括信号源误差、采集序列的谐波失真、噪声及非谐波失真、抖动、软件拟合运算误差等。结合一个实例,给出了通道间延迟时间差测量不确定度的评定结果。该过程可用于相应计量标准的不确定度分析与评定。     

波形记录仪触发延迟的测量不确定度评定

提出了使用正弦波激励评价波形记录仪触发延迟的新方法,通过一个波形在有触发延迟和无触发延迟时,采集序列间的相位差对应的时间差来最终判定触发延迟结果。讨论了影响评价结果不确定度的几个主要误差来源,包括信号源误差、采集序列的谐波失真、噪声与非谐波失真、抖动、软件拟合运算误差等,同时给出了不确定度评定结果。以一组实验结果验证了所述方法的有效性和切实可行性。     

一种电能及功率的精确评价方法

目的 介绍了一种用于精确评价正弦交通电电能及功率既简单又实用的方法。方法 使用数据采集系统及正弦波拟合法评价电能及功率参数。结果 与其他方法相比,该方法可同时给出正弦电压及电汉的幅度、频率、相位差、功率和功率因数等参量。结论 该方法指标评价全面,所有指标均可有效溯源到电压、电流和频率这些基本量上。分析了评价过程的误差来源,获得减小其评价误差的方法。其核心技术除了波形拟合外,还采用了一种性能独特的单频数字滤波器技术来减小评价结果的不确定度,并阐述了滤波方法及过程。     

用正弦波拟合法评价数据采集系统的通道时延时

本文介绍了数据采集系统通道间延时的一种简单实用的评价方法，讨论了评价过程的误差来源，以及减小其评价误差的几种对策；同时，给出了评价过程的计算机仿真结果。     

数据采集系统通道采集速率评价中的几个问题

介绍了一种简单实用的数据采集系统采集速率的方法，讨论了评价过程的误差来源，以及减小其评价误差的几种对策；同时，给出了评价过程的计算机仿真结果。     

正弦波拟合参数的不确定度评定

介绍了用4参数正弦波最小二乘拟合法拟合参数不确定度分析和评价过程。讨论了主要的不确定度来源,包括信号源误差、采集序列谐波失真、采集序列噪声及非谐波失真、采集序列中信号周期抖动、软件拟合运算误差的影响等,给出了减小不确定度的主要措施。结合一个幅度拟合实例给出了评价结果。     

一种基于残周期正弦波拟合的相位差测量方法

针对不足一个波形周期的相位差测量,提出使用残周期正弦波拟合算法实现的技术方法,给出了原理和实现过程。针对该条件下相位差的测量不确定度,给出了使用波形局域失真和噪声信号比方式,以实际估计参数条件下的仿真计算进行评估的模式。最后,使用激光测振仪校准中的三个相位之间的相位差进行了实验验证,结果表明,在约0.5个周期条件下获得的相位差与多周期条件下的相位差仅仅相差1°左右,证明了该方法的有效性和可行性,为正弦相位差测量提供了一种新的实现方式。     

Full-field phase error compensation method based on relationship between unwrapped phase and phase error

The three-dimensional reconstruction in phase-measuring profilometry (PMP) usually involves the phase error caused by the gamma effect of the projector. In this study, the relationship between the unwrapped phase and the phase error of every pixel is analysed, and an effective full-field phase error compensation method based on this relationship is proposed for the reduction of every pixel error. In our optimized PMP system, the full-field phase error can be detected by directly fitting the unwrapped phase of the reference plane. In addition, the relationship between the unwrapped phase and the phase error can be established by creating a phase-error lookup table for the phase error compensation of every pixel. The experimental results demonstrate the effectiveness of the proposed method in practical PMP, and the measurement errors can be reduced by a factor of least 10.     

基于微分法的新相位测量轮廓术

在相们测量轮廓术中，为了得到真实相位值，必须进行相位解包裹处理的繁琐过程，为此提出一种可以直接获得真实相位值的新算法。这种算法的原理是空域中的微分（一阶）等效于频域中乘以一个线形因子，由此得到相位微分与光强的关系，求出相位的微分值后将其积分就获得相位的真实值。计算机仿真显示该方法确实有效可行。     

A practical method to process time and frequency signal

A new practical time and frequency signal processing method can be used to generate an accurate time signal, for stable phase step, for frequency change and synthesis, and for other related uses. The method accomplishes the time and frequency signal processing by changing the period and phase of the machine cycle of a microcomputer. It is based on pulse deletion of a high frequency clock signal, quantified phase delay, and other intentional variations in a microcomputer clock signal circuit. The pulse deletion and phase delay can be implemented periodically or individually for different purposes, and a frequency change and synthesis or phase shift of the microcomputer output signal can be obtained. With this method, the time signal processing precision can be from several tens of nanoseconds to less than 1 ns.     

Accurate measurement of power, energy, and true RMS voltage usingsynchronous counting

A synchronous measurement method that can be applied for the accurate determination of periodic signals is presented. The method relies on adaptation of the measurement time to the period of the measurement signal. It is based on dual-slope integration performed according to the synchronization signal (input signal). The first phase of integration is fully synchronized with the input signal. The time of the first phase is also measured. The output voltage of the integrator depends directly on the input signal and the time of the first integration phase. Measurement values are the results of arithmetic operations between the time of the second phase of integration and the measuring time (first phase). With this method, an accuracy of 0.1% can be achieved     

Phase-step calibration for phase-stepped interferometry

A novel method to set the proper phase steps, as used in phase-stepped interferometry, is presented. It is indicated how and when this method can be used. With only two images one can deduce the relative phase step between them by calculating the correlation between the two images. The error of the proposed method is shown to be smaller than 0.1%.     

Temporal phase unwrapping and its application in shearography systems

Temporal phase unwrapping is applied to a two-camera polarization phase-stepped system. A simple algorithm for the phase-change calculation is given, together with simulations, to indicate its validity and strength. This method can be applied directly for detection of phase changes as a function of time. It is proposed to use this method in a shearography setup. The phase distribution in the shearogram can then be obtained, without the standard 2pi ambiguities, by application of the required total shear in a number of smaller steps, provided that each step is small enough to be free from these 2pi phase steps.     

Spatial mismatch calibration using circular carrier technique in the simultaneous phase shifting interferometry

In most simultaneous phase shifting interferometry (SPSI) systems, a group of phase shifting interferograms are captured simultaneously at the different physical locations to retrieve the phase. The data of different interferograms should be spatially matched correctly, which is hard to realize by existing methods or this spatial mismatch will lead to phase retrieving error. In this paper, a spatial mismatch calibration method is proposed, where the circular carrier is introduced in the interferograms of the SPSI system, and the modulating phases of any two interferograms can be retrieved by the demodulation technique of circular carrier interferogram. The slope of the difference between these two phases is proportional to the mismatch value, so this error can be extracted and the experiment setup calibrated. The main error sources of the proposed method are analyzed with the conclusion that its match precision can be achieved up to 0.5 pixel. In addition, the simulated interferograms and actual interferograms captured in a SPSI system are processed to validate our proposed method.     

频谱分析中用于相位和频率校正的相位差校正法

提出了一种对连续时域信号分前后两段作傅里叶变换,利用其对应离散谱线的相位差校正出谱峰处的准确频率和相位的新校正方法——相位差校正法,通过窗谱函数的公式还可以校正其幅值,以解决离散频谱分析中由于谱峰谱线没有对正峰顶时所带来的较大误差。该方法原理简单,通用性好,运算速度快,校正精度高,可以在不知道窗谱函数表达式的情况下,直接用其相位差进行求解。仿真研究表明,对单频率成分的频率、相位、幅值进行校正,频率误差小于0.0002个频率分辨率,相位误差小于0.1 度,幅值误差小于0.02% 。     

Holographic data storage using an optimized phase mask

Abstract

A method for reducing the reconstruction error and improving the spectral distribution in holographic data storage has been proposed. An optimized phase mask is introduced into the optical system. By using the phase mask, the reconstruction error and uniformity of the spectral distribution can be optimized. The relative importance between reconstruction error and uniformity can be emphasized with an adjustable weight factor. The phase mask can be designed by using amplitude-phase retrieval algorithms. Simulation results have shown the merits of the proposed method. The feasibility of optical realization is investigated briefly.