On the relation between the wave aberration function and the phase transfer function for an incoherent imaging system with circular pupil

The consideration is carried out in its general formulation: the wave aberration function is represented in terms of classical aberrations (the Zernike polynomials), the phase transfer function (argument of the complex optical transfer function) is defined by a chain of transformations originating from the generalized pupil function. Quasi-analytical quadrature formulas are derived that link the optical transfer function and the phase transfer function with the aberration terms. It is shown that the phase transfer function contains information on the odd-order aberrations, which can be retrieved from coefficients to the Taylor expansion of the derived quadrature relation. Received 16 June 2001     

N2+分子离子的B2Σu+、A2Πu和X2Σg+电子态光谱研究

采用光外差-磁旋转-速度调制吸收光谱技术, 在可见光波段范围16800～17573 cm-1, 对N2+的A 2Πu-X 2Σ+g(12,6)、(11,5)、(7,2)带和B 2Σ+u-X 2Σ+g (1,5)带进行了测量和分析,推导了双原子分子振转能级在受到微扰作用时的有效哈密顿量形式,并分析了N2+的A 2Πu-B 2Σ+u之间存在的微扰相互作用,通过与实验数据的拟合得到了精确的电子态微扰常数ξe、ηe .     

Observation of the modulation instability and frequency-doubling in self-defocusing crystal

We report on the experimental observation of the modulation instability of uniform beam and frequency-doubling of interference fringes spatial frequency in self-defocusing photorefractive crystal LiNbO₃:Fe by the same experimental setup. Frequency-doubling appears if the nonlinearity of the c-axis is bigger than the modulation of the cylindrical lenses, otherwise the modulation instability appears.     

光弹性贴片载波法

本文提出了一种提高测量灵敏度的光弹性贴片法。通过高频条纹调制获取载波条纹图。使贴片的等差效应所反映的力学信息规范化。运用计算机图象处理技术,对载波图自动采集、处理和解调,以获得全场条纹级数。编制了专用软件并以实例说明实验过程。     

Integrated modulation intensity distribution as a practical tool for condition monitoring

Modulations present in vibration signals generated by rotating machinery might carry a lot of useful information about objects’ technical condition. It has been proven that both gearboxes and rolling element bearing (REB) faults manifest themselves as modulations. The paper describes a technique for detection of modulations in vibroacoustic signals, called modulation intensity distribution (MID), which is a function that combines multiple spectral correlation densities in one way or another, depending on the application. Additionally, the paper describes a functional obtained by integrating an MID (denoted by IMID) that has the advantage of being a function of only one frequency variable instead of two. The paper investigates the utility of the MID as an indicator for detection of the presence of rolling element bearing faults in high noise environments. For the purpose of testing, a wind turbine that suffered both advanced gearbox fault and early stage of bearing fault was chosen. Additionally, the paper undertakes the problem of application of the proposed tool in an industrial condition-monitoring system. In order to show the behavior of cyclic components generated by the turbine under study over a long period of time, the set of MIDs integrated over full range of potential carrier signals was presented as a cascade plot.     

温箱控制器的运行控制文件测试与研究

为了建立综合控制台对温度试验箱进行集中控制,需要对各独立的温控试验箱的运行文件进行分析和整合,形成可被温控试验箱执行的*.PRG程序文件。方法是首先通过原系统操作界面程序,设定温箱工作温度和时间,产生一个温箱控制器执行的*.PRG文件。然后,用Beyond Compare工具,对此(二进制)文件进行测试分析,得出文件的开始标志,温度阶梯步数,温度值单元,温度点切换时间单元,切换点行标志和文件结束标志等6个部分的位置关系,从而获得温箱控制器运行文件*.PRG的内部结构。根据文件内部数据结构关系,可以建立符合原*.PRG文件格式且可通用的可执行程序文件。在某型综合控制台的设计中采用该方法建立的*.PRG文件对各试验箱进行独立运行实验,实现了对温箱的综合控制。     

航空相机动态调制传递函数分析与研究

影像位移是影响航空相机分辨率的主要因素。用MTF对动态成像质量做出评价,确立合理的稳定系统性能指标,是设计过程中常用的手段。为此研究了匀速运动,变速运动和正弦运动条件下的动态MTF,针对目前无法准确评价的低频正弦运动,提出了基于离散相位区间的动态MTF计算方法。分析结果表明,在像模糊斑大小相同的情况下,高频振动对像质的破坏最严重,直线运动次之,低频振动最轻。根据所作分析可以针对给定的影像位移计算出相应的动态MTF,为航空相机像质评价提供了准确定量的参考。     

基于光纤光参量放大的光脉冲压窄技术的研究

在高重复频率的光窄脉冲源中,为了获得更窄的脉冲,需要增加泵浦功率|但泵浦功率的提高会使光放大器的增益趋于饱和,放大的自发辐射噪音增强,脉冲光信噪比下降.为此,提出了利用啁啾管理和光纤光参量放大相结合的脉冲压窄方案.将强度调制后的泵浦光通过相位调制引入线性负啁啾,由于经参量过程后在新的闲频光上啁啾会加倍,从而进一步增大了信号的谱宽,并通过色散补偿介质实现了光脉冲压缩.实验给出了10 GHz速率下的结果,通过泵浦光的相位调制在0.5 W平均泵浦光功率条件下得到了脉宽19 ps的光脉冲,结果与理论分析基本吻合.     

基于调制方向提取载波散斑条纹中心线的方法

条纹中心线法是一种重要的电子散斑干涉条纹解调方法,其前提条件是获得高准确度的条纹中心线.本文在分析载波电子散斑干涉条纹自身特征的基础上,提出了一种基于载波条纹调制方向提取条纹中心线的方法.该方法首先通过同态滤波有效滤除高频乘性散斑噪音,提取出载波条纹;然后应用基于调制方向提取中心线算法确定载波条纹灰度极值点并做二值化处理;再采用基于中心线拟合或者基于条纹间距的边沿中心线补偿法,获得完整的条纹中心线图.实验结果表明:该方法简单、可靠,能快速、准确地提取出连续的中心线.