Synchronous Digital Averaging of Time Signals

In this article a method of studying the falling edge of a time signal in detail is presented. Preliminary results have shown that the arrival time of a time signal can be determined with the same phase stability as that of the carrier.     

On the Enhancement of the SNR of Repetitive Signals by Digital Averaging

A simplified technique to improve the signal-to-noise ratio (SNR) of repetitive signals by digital averaging is presented. The technique uses a threshold detector and a memory instead of the analog-to-digital converter and memory, which is the common practice. It is shown that if the SNR of the measurements is small and the number of averaged measurements is large then the SNR of the resulting signal is smaller but comparable to that obtained by the usual procedure. The nonlinear distortion introduced by the process is also discussed.     

Performance Improvement of a DSP-Based Digital Integrator for Magnetic Measurements at CERN

An improved self-calibrating digital instrument for online flux measurements on superconducting magnets for particle accelerators prototyped at the European Organization for Nuclear Research (CERN), in cooperation with the University of Sannio, is presented. The new instrument reduces the online flux analysis time down to 4.00 $muhbox{s}$ within a resolution of 50 ns. Furthermore, the typical signal-to-noise-and-distortion ratio (SINAD) is significantly improved with respect to the previous version and to the instruments that are currently in use. Details about the design, online measurement principle, and results of the metrological characterization of the new instrument are provided.      

High-Resolution Digital Integral Photography by use of a Scanning Microlens Array

We suggest what we believe is a new three-dimensional (3-D) camera system for integral photography. Our method enables high-resolution 3-D imaging. In contrast to conventional integral photography, a moving microlens array (MLA) and a low-resolution camera are used. The intensity distribution in the MLA image plane is sampled sequentially by use of a pinhole array. The inversion problem from pseudoscopic to orthoscopic images is dealt with by electronic means. The new method is suitable for real-time 3-D imaging. We verified the new method experimentally. Integral photographs with a resolution of 3760 pixels x 2560 pixels (188 x 128 element images) are presented.     

Speckle Reduction by Unidirectional Averaging

It is shown that for the holographic reconstruction of diffuse objects the use of a vibrating coherent source decreases the contrast of the speckle pattern, and that for certain classes of objects resolution is not affected. This is true in particular for grating-like objects when the source is vibrated in a direction parallel to the lines of the grating, and an important application is to the pattern of straight, parallel fringes commonly obtained in holographic interferometry. When a more complex object is used, the speckle reduction would be accompanied by a loss of resolution.     

AFM扫描图像重构算法的改进

针对原子力显微镜（AFM）纳米成像中存在的失真问题,研究了通过探针建模实现AFM扫描图像重构方法.目前探针盲建模算法在重构AFM图像时存在较大误差,因此提出基于探针模型预估计的AFM扫描图像重构方法.该方法采用分区探针针尖建模,并通过基于该探针模型的反卷积运算实现AFM扫描图像重构,获得比较接近真实形貌的AFM扫描图像.文中介绍了算法的具体步骤,通过仿真和实验结果证明,该方法能够有效降低AFM图像重构时引入的误差,得到的图像更能反映样品表面真实的形貌.     

Blackbody calibration sources of high accuracy for a spaceborne infrared instrument: the Along Track Scanning Radiometer

We describe the two 140-mm-aperture simulated blackbody sources used for the on-board calibration of the Along Track Scanning Radiometer, a spaceborne thermal infrared instrument for the accurate remote sensing of sea surface temperature, in operation since 1991. The design of these spaceborne sources, which operate at ≈ -10 °C and ≈ +30 °C, allows them to meet their unprecedented accuracy goal, namely a 3σ uncertainty in their brightness temperature of <0.1 K for the whole mission. This performance is empirically demonstrated in the laboratory and in flight by long-term temperature readout tests, temperature uniformity measurements, and direct emissivity measurements.     

参考数字多用表直流电压的测量及不确定度评定

按照直流数字电压表检定规程中给出的标准传递法,对数字电压表进行测量,并根据不确定度评定方法,对直流电压的测量结果进行了不确定度评定.     

纸板数字包装印刷的性能

卡纸材料上的数字印刷是一种近期发展起来的新技术.为了能成功地在卡纸上进行数字印刷,研究卡纸材料的印刷走纸性能、着墨性能和印刷质量,了解卡纸的表面性能与印刷之间的关系是卡纸数字印刷技术面临的首要问题.本文主要研究了纸板的印刷性能、数字印刷工艺对纸板的要求、影响纸板数字印刷对成品质量的因素.     

Investigating Averaging Effect by Using Three Dimension Spectrum

The eddy current displacement sensor＇s averaging effect has been investigated in this paper, and the frequency spectrum property of the averaging effect was also deduced. It indicates that the averaging effect has no influences on measuring a rotor＇s rotating error, but it has visible influences on measuring the rotor＇s profile error. According to the frequency spectrum of the averaging effect, the actual sampling data can be adjusted reasonably, thus measuring precision is improved.     

航摄底片扫描数字化生产的质量控制

如何高精度高质量地对航摄底片进行扫描数字化生产,并对生产过程及成果进行质量控制与检查,确保数字化影像数据准确可靠,是保证全数字摄影测量成图成果质量的一个基础环节。文章围绕这一环节,并结合笔者多年来管理扫描数字化生产的实践经验,就原始底片扫描的硬件平台、软件模块及生产过程的质量控制进行论述。     

Radiometer for ensuring traceability of measurements by sensitive infrared detectors

An analysis is made of the errors and results of metrological certification of standard (reference) irradiance and radiance radiometers. Translated from Izmeritel'naya Tekhnika, No. 12, pp. 31–34, December, 1997.     

Characterization of an Ellipsoidal Radiometer

An ellipsoidal radiometer has been characterized using a 25 mm variable-temperature blackbody as a radiant source. This radiometer is intended for separating radiation from convection effects in fire test methods. The characterization included angular response, responsivity, and purge-gas flow effect studies. The angular response measurements showed that the reflection from the radiometer cavity was higher on one of the cavity halves relative to the other half. Further development work may be necessary to improve the angular response. The responsivity measured with reference to a transfer-standard electrical-substitution radiometer showed dependence on the distance of the radiometer from the blackbody cavity. The purge-gas had the effect of reducing the signal output nearly linearly with flow rate.     

一种抗印刷-扫描倾斜失真的数字水印算法

设计了一种用于彩色印刷防伪图像的基于博奇编码的傅里叶计算全息数字水印方法。通过印刷-扫描实验,研究了扫描过程图像倾斜角度与提取的水印质量之间的关系。实验表明:该水印算法对印刷、扫描过程中的倾斜攻击等具有很好的鲁棒性,能满足彩色印刷图像的防伪要求;且倾斜角度越小( <15°),对水印质量的影响越小,倾斜角度为45°时提取的水印质量相对于其他倾斜角度下提取的水印质量略好。     

微弱辐射测量仪的研制

本文介绍一种高灵敏，宽动态范围的辐射测量仪的研制情况，着重对线路的噪声性能进行了分析，并据此完成了元件的选择。文中还给出了仪器达到的指标。     

往复数字滤波器及其性能分析

根据实际数据处理工作的需要 ,以减小信号相移量为目标 ,提出一种新的数字滤波算法 ,即所谓往复数字滤波器。从滤波效果出发 ,拟定了一组性能评价指标 ,并应用数学试验方法在拟定的评价指标下 ,对该算法与传统算法进行了性能对比分析。分析结果表明 ,该算法在信号的相位偏移、幅值衰减、波形畸变以及除噪能力和滤波效率等方面均优于传统算法。该算法结构简单、编程容易、占用存贮空间少、运行速度快 ,可适用于动态测试数据的预处理。     

Mechanical Performance Improvement of Low-Density Polyethylene Blends

Mechanical properties of recycled low-density polyethylene have been improved by using calcium carbonate as a filler. Compatibility of the filler with a matrix is not sufficient to lead to materials with good elongation at break. This compatibility has been increased by introducing 5 or 10% of compatibilizers as triblock copolymers of styrene and butadiene modified with maleic anhydride. Good results have also been obtained by direct grafting of maleic anhydryde onto recycled low-density polyethylene.     

改进射线数字成像系统的图像质量

目的 改善射线数字成像系统的图像质量。方法 在射线数字成像系统中,存在许多影响图像质量的因素,这些因素来源于系统的各个成像环节,如CCD相机、成像屏、X射线源、被测物体、控制电路、射线散射等,它们对成像质量造成严重影响。作者针对DR成像系统降低图像质量的因素作了分析,并通过校正和图像处理的方法使其得到了抑制。结果 提出了改善射线数字成像系统图像质量的方法。结论 通过实际应用,表明所提出的方法是有效的。     

Computer Modeling of an Optical Radiometer

The problem is considered of creating a uniform structure for the various categories of a standard for the unit of average laser radiation power. The approach is based on directly synthesizing the structure of a standard instrument. As an example, a computer modeling is carried out of a combination which is typical for many types of measurement, namely a measurement transducer and a voltmeter, and this was applied to the case of measuring average laser radiation power.