数字条纹投射技术中改进的非线性校正方法

在数字条纹投射技术中,系统的非线性是影响投射条纹质量的主要因素,其直接导致变形条纹中出现高次谐波,从而影响系统的测量精度。提出了一种系统非线性校正的新方法,利用N阶多项式拟合代替传统的单一伽马参数表示系统的非线性关系,并依据条纹图像累积直方图匹配方法,通过迭代操作同时求得系统非线性关系和较高精度的物体位相分布。计算机模拟及实验结果表明,该方法能够有效地抑制系统非线性的影响,获得理想的物体位相分布,从而验证了该方法的可行性。     

Measurements of electron density, temperature and photoionization cross sections of the excited states of neon in a discharge plasma

In the present work emission and absorption spectroscopy have been used to determine the plasma parameters of neon in a hollow cathode discharge lamp. The excitation temperature is determined using the intensity ratio method and Boltzmann's plot method whereas the electron density is determined from the Stark broadening of the spectral lines. The behavior of the optogalvanic signal as a function of laser energy has been studied for three transitions from the 2p⁵3s [1/2]₂ metastable state following ΔJ=ΔK=0, ±1 dipole selection rules. The saturation technique has been used to measure the photoionization cross section from three intermediate states 2p⁵3p′ [1/2]_1, 2p⁵3p′ [3/2]₂ and 2p⁵3p [5/2]₃ up to the 2p^{5 2}P_1/2 ionization threshold.     

基于过抽样Gabor变换的核磁共振FID信号增强算法

基于作者先前提出的过抽样实值离散Gabor变换,本文提出了一有效的算法用于核磁共振自由感应衰减（NMR FID）信号的减噪. 由于NMR FID信号在时域中是一短暂的振荡衰减信号,使得变换后的NMR FID信号能量在时频域中集中在少数变换系数上,而噪声则遍布在整个变换系数上,因此通过对变换系数幅度进行阈值限制方法可达到明显地增强NMR FID信号的目的. 文中在理论和模拟实验上分析表明,过抽样Gabor变换比临界抽样Gabor变换更适宜于NMR FID信号的减噪,因为在过抽样条件下比在临界抽样条件下的综合窗及其对应的分析窗,无论是在时域中还是在频域中都可具有更好的局域分布集中性,同时,Gabor变换在过抽样条件下也比在临界抽样条件下具有更高的时频精度.     

掺铒光纤激光器自混合理论与微振动位移测量

利用线形掺铒光纤激光器搭建了一种新型光纤传感测量系统来测量微振动位移.采用条纹计数法分析自混合干涉信号,实验显示扬声器的振幅与驱动电压成很好的线性关系.该实验装置结构简单、成本低.实验结果表明,用该传感系统来进行振动位移测量,信号稳定,方法简单、迅速.     

Detection of multi-frequency weak signals with adaptive stochastic resonance system

Aiming at the poor detection rate of multi-frequency weak signals under a strong background of noise, a novel method based on adaptive stochastic resonance (SR) theory is proposed in this paper. The optimal parameters can be obtained automatically via measurement by establishing an adaptive SR system model and using the reverse location method. After passing through the adaptive SR system, the spectrum values of all eight signals greatly improve, the largest spectrum value gain increases from 12.41 to 2033 when the frequency is 0.01?Hz, which is an improvement of a factor of 162.8, and the signal-to-noise ratio (SNR) gain of the whole system is 10.3134?dB. Under the condition of different input noise intensities and signal amplitudes, the mean SNR of the system increases from –13.1136 to –2.7614?dB, which is a 78.9% increase, and the largest SNR gain is 13.4702?dB when the noise intensity D?=?1.2 and signal amplitude A?=?0.11. Compared to the single optimal spectrum value, when defining multiple optimum spectrum values as the SNR criterion, the detection sensitivity is less than 0.35 when the input noise intensity is between 0.5 and 2.5, and the sensitivity value is 6.29 times higher when D?=?2.5. The system successfully realizes the adaptive detection of twelve weak signals, and the SNR gain is 7.9743?dB, which improves the channel capacity of signal detection. The experimental results demonstrate the high efficiency and strong applicability of the system, improving the signal processing efficiency and speed of signal transmission.     

Application of robust color composite fringe in flip-chip solder bump 3-D measurement

This study developed a 3-D measurement system based on flip-chip solder bump, used fringes with different modulation intensities in color channels, in order to produce color composite fringe with robustness, and proposed a multi-channel composite phase unwrapping algorithm, which uses fringe modulation weights of different channels to recombine the phase information for better measurement accuracy and stability. The experimental results showed that the average measurement accuracy is 0.43μm and the standard deviation is 1.38 µm. The results thus proved that the proposed 3-D measurement system is effective in measuring a plane with a height of 50 μm. In the flip-chip solder bump measuring experiment, different fringe modulation configurations were tested to overcome the problem of reflective coefficient between the flip-chip base board and the solder bump. The proposed system has a good measurement results and robust stability in the solder bump measurement, and can be used for the measurement of 3-D information for micron flip-chip solder bump application.     

α稳定噪声下一类周期势系统的振动共振

将多个低频微弱信号、高频信号和加性α稳定噪声共同激励的一类周期势系统作为研究模型,以平均信噪比增益(MSNRI)为性能指标,对α稳定噪声环境下周期势系统中的振动共振现象进行了研究,分别探究了α稳定噪声的特征参数α、对称参数β、加性噪声强度放大系数D、高频信号幅值B以及频率?对振动共振输出效应的影响.研究结果表明:1)在不同分布的α稳定噪声环境下,固定频率?(或幅值B),当幅值B(或频率?)逐渐增大时,MSNRI-B(或MSNRI-?)曲线出现多个峰值,即存在多个B区间(或?区间)可诱导振动共振,并且这些区间不会随噪声分布参数α或β的变化而变化;2)当加性噪声强度放大系数D发生变化时,幅值B和频率?的共振区间没有随着D的变化而变化,表明只有高频信号能量向待测低频信号转移,噪声能量并没有向待测低频信号转移.另外当幅值B、频率?固定时,随着D的逐渐增大,依然可以实现微弱信号的检测,表明振动共振可以克服工业现场噪声强度不可调控的缺点.本文研究结果提供了一种新的微弱信号检测方法,在信号处理领域有着潜在的应用价值.     

基于PS12台阵的微弱爆炸信号识别技术

对GSN台网的HIA地震台站与CTBTO/IMS的PS12地震台阵记录的2007年12月11日河北怀来“明灯1号”爆炸及2006年10月9日朝鲜爆炸事件进行对比分析。结果显示:PS12台阵子台监测的P波信噪比提高至普通台站监测的P波信噪比的4.6倍;利用聚束技术进一步压低噪声后,PS12台阵聚束信号的信噪比提高至单个钻井台站的3倍,比普通HIA台站记录的地震信号信噪比高10多倍。研究结果表明,钻井小孔径台阵可高效提高微弱信号的检测能力。     

基于影像处理的干涉测量相位重构研究

随着计算机技术和光电成像元件的发展,影像信息处理技术已经在无损检测、医学检测以及干涉测量等领域得到广泛应用。本文主要研究了影像信息在干涉测量领域的波前相位提取方法。干涉条纹图是干涉测量领域中影像信息的载体,在干涉条纹处理方面,针对空域卡雷算法的特点,提出一种基于影像处理的单幅闭合干涉条纹图相位重构新算法。在空域卡雷算法处理方法的基础上,利用迭代修正算法对干涉图相位进行二次逼近,实现了对单幅干涉条纹图的高精度相位重构。Matlab仿真结果表明,迭代修正后的相位残差降低了25.8%,表明该算法在空域卡雷算法的基础上能够有效提高相位重构精度,实现干涉测量领域中影像信息的高精度处理。