A generalized temporal phase unwrapping algorithm for three-dimensional profilometry

A generalized temporal phase unwrapping algorithm is proposed for absolute phase measurement of object surfaces with complex topography. We first make comments on error analysis of various temporal phase unwrapping (TPU) algorithms and point out problems existing in these techniques. We present a generalized TPU algorithm (GTPU), which eliminates some limitations imposed on the fringe sequence for the classical TPU algorithms. So the desired number of fringes can be determined according to practical situation, leading to a flexible method for phase reconstruction. In addition, compared with the classical TPU algorithms, GTPU has better noise immunity and less computational complexity. Theoretical analysis and experiment results are presented to show the validity of the proposed algorithm.     

Phase deviation analysis and phase retrieval for partial intensity saturation in phase-shifting projected fringe profilometry

Intensity saturation may take place as a sinusoidal fringe pattern is projected onto an object which has a relative high reflective index on some regions of the surface. If a phase-shifting method is used, the illuming light intensities at the same point of the object may have different values for each projected phase-shifting fringe pattern. Therefore, when the intensity at a point of the object exceeds the saturation level for a certain phase step of projected fringe pattern, other intensities obtained at the same point with different phase steps of projected fringe patterns do not exceed the saturation level. This kind of saturation is defined as partial intensity saturation. In the case of partial intensity saturation, a relative larger phase error is introduced when a conventional phase reconstruction algorithm is used in the phase-shifting projected fringe profilometry (PSPFP). To get rid of such disadvantage, an improved algorithm for phase reconstruction is proposed in this paper. By using the new algorithm, the effect of partial intensity saturation for the phase reconstruction can be decreased greatly and a good quality of reconstructed phase map can be obtained. Phase deviation of the reconstructed phase is also analyzed. Finally, an experimental result with PSPFP is presented to validate the feasibility of the proposed algorithm.     

激光告警散射截获距离仿真

针对近地面来袭的激光威胁源,建立基于米氏散射理论的散射探测模型。利用matlab软件对散射光光强随激光探测方向、大气能见度的变化进行了数值分析,结果表明,探测散射光最强的方向是平行于主轴传输方向,大气能见度和散射光强成非线性关系。在分析散射光强受气象条件变化的基础上,得到了不同激光威胁源情况下,激光告警的最大散射截获距离。     

迈克尔逊干涉仪光程差公式及条纹特点详解

本文通过对迈克尔逊干涉仪干涉原理和平涉光路的探讨,详解了迈克尔逊干涉仪进行干涉对的光程差公式;对条纹密度特点进行了进一步说明。从理论分析方面为使用迈克尔逊干涉仪提供了更明晰的帮助。     

一种基于非下采样Contourlet变换多聚焦图像融合算法

针对现有小波类图像融合算法的不足,提出了一种基于非下采样Contourlet变换多聚焦图像融合算法,并在Contourlet域中引入了局部区域可见度以及局部方向能量的概念.针对低频子带系数和各带通方向子带系数分别提出了基于局部区域可见度以及基于局部方向能量的系数选择方案.通过对多聚焦图像融合的仿真实验,表明该算法相对于传统的基于离散小波变换和离散小波框架变换融合算法能够有效减少有用信息的丢失以及虚假信息的引入,同时能够从源图像中提取更多的有用信息并注入到融合图像中, 得到更好视觉效果和更优量化指标的融合图像.     

干涉条纹计数法光纤Fabry-Perot腔液位传感器

提出一种抗光源波动和外界干扰的条纹计数法光纤Fabry-Perot腔干涉型液位传感器.为适应这种条纹计数法对应变大挠度的要求,采用波纹管作应力弹性元件;对干涉条纹走向(或液位升降判向),分别提出实用的硬件设计方案和计算机软件处理办法;给出一种腔长温度补偿设计;实际制作了双光路光纤Fabry-Perot腔液位传感器,进行了实际气压模拟试验和实际水位测量试验,取得了良好结果.     

纵向莫尔条纹在自准直仪中的应用

为了提高自准直仪的分辨力,将纵向莫尔条纹引入到光路中,用长光栅代替传统单狭缝,将长光栅成像在CCD检测器上,CCD作为标尺光栅,通过两个光栅叠加形成的莫尔条纹的变化可以将成像位移分辨率提高到亚像元,进而将自准直仪的角度分辨率提高到毫秒级.实验结果表明,相对于直接检测狭缝边缘的方法,莫尔条纹法的分辨力提高了25倍.     

条纹法提高成像分辨率的实验研究

 对利用条纹场照射目标以提高成像分辨率的方法进行了实验研究。条纹法提高成像分辨率的基本思想是,采用余弦条纹场照射目标,光学系统截止频率外的一部分高频分量将通过光学系统,通过对用多幅同频条纹场照射目标所获得的图像序列进行综合处理,可以获得超分辨率的图像。实验采用激光形成的干涉条纹场照射目标,共采用10幅余弦条纹场,各幅条纹场之间依次有1/10个周期的平移,对这10幅条纹场照射目标时所拍摄的图像进行综合处理,获得了分辨率提高的图像。实验结果证明了利用干涉条纹场照射目标获得超分辨率像这一方法的可行性。     

Visibility Graph Analysis of Reservoir-Triggered Seismicity: The Case of Song Tranh 2 Hydropower,Vietnam

In this study, the visibility graph analysis of seismicity triggered by Song Tranh 2 hydropower (Vietnam) is performed. The relationship between the seismic (the Gutenberg–Richter b-value) and topological (the k–M slope) parameters of seismicity is analysed. Our findings indicate that the relationship between the Gutenberg–Richter b-value and the k–M slope of the investigated seismicity is in agreement with that characterising the tectonic seismicity. The results obtained from analysing the reservoir-triggered seismicity of Song Tranh 2 area could contribute to better characterisation of the relationship between the seismological and topological parameters of seismicity, strengthening the universal character of the relationship between the b-value and the k–M slope.