Dynamic observation of vortices in superconductors using a holography electron microscope

Individual vortices in superconductors are directly observed with our holography electron microscope. Vortices cannot be viewed as an electron micrograph, but only as a holographic interference micrograph or a defocused micrograph (Lorentz micrograph), since vortices are phase objects to the illumination electron beam. Since the flux itself, and not its replica, is detected, even the dynamic behavior can be observed. The dynamics of vortices in a Nb thin film can be observed in real time when the sample conditions, such as the temperature or the applied magnetic field, change.     

计算机全息法实现光学图像假彩色编码

通过对原始图像进行假彩色编码,可提高图片的灰度差异,再现图片细节.该项技术广泛应用于材料样品组分的显微成像.提出了一种新的假彩色编码方法,利用计算机程序控制实现光栅条纹图案定义及输出,通过再次光学缩拍技术在胶片上制作衍射光栅,实现了图片的假彩色成像.与传统方法相比,该项技术具有成本低、颜色编码足够丰富,制作过程简单灵活等优点.     

正交读出方式体全息光栅通信波长衍射特性

为了寻求高质量和高密度的密集波分复用器件,采用了在双掺铟铁的铌酸锂晶体中透射式记录/正交式读出方案制作体全息光栅的方法,对体全息光栅衍射特性进行理论分析和实验验证.利用波长为532nm的激光记录尺寸比为1:1的体全息光栅,然后用中心波长为1550nm的红外通讯波长成功读出,取得了波长选择性为0.5nm的波长衍射特性数据.同时,利用2维耦合波理论的闭形式解析解得到了该体全息光栅衍射效率随波长的变化关系.结果表明,实验结果与理论预期相符合,这一方法对制作体全息光栅密集波分复用器件的实用化是有帮助的.     

数字全息光电再现实像与人的交互

为了提高交互的自然性,提出用正交双目摄像机检测空间中的手指作为输入,引导全息影像显示的交互方法.在介绍交互原理的基础之上,分析了手指运动和像的变化,建立了两者的映射关系.在交互的实现上,通过计算全息预先得到场景的数字全息图序列,然后根据检测到的手指信息加载相应的全息图进行光电再现,即可达到数字全息光电再现实像的动态交互显示的效果.最后,孔雀全息再现像与人的交互实例验证了提出方法的有效性和可靠性.     

数字合成全息系统中空间光调制器DMD的研究

研究了数字合成全息系统(DSHS)中数字微反射器(DMD)的光学反射衍射混合的性质,解释了入射光入射角度任意性而不必拘泥于20°的原因,对DMD反射衍射混合成像的特性从其微结构角度进行了分析,特别注意了微反射镜的镜轴方向对图像成像区域和图像灰度的影响。针对DMD的性质设计了实验并得出了结果,用DMD作空间光调制器(SLM)实现了DSHS的设计。     

全色高分子全息记录材料的研究

针对Ar^ 激光器、He-Ne激光器三基色波长,设计了4种有效的光敏引发体系;给出了制作全色全息干版的工艺。实验结果表明,用其所所摄彩色反射全息图质量好,重建图像清晰、明亮。     

数字同轴和数字离轴全息系统分析

利用最高空间频率分析法,通过逐点分析记录在 CCD 上的空间频率信息,研究了物体可允许记录的最大横向尺寸、最小记录距离、全息图的信息量、空间分辨力、再现像的横向分辨力、轴向分辨力及散斑大小,并得到了数学表达式。理论分析和实验结果表明,数字同轴全息系统放宽了对 CCD 分辨力的要求,有较高的分辨力,较低的散斑噪声、灵活、简单的系统结构及较高的 CCD 空间带宽利用率,在增强系统性能方面要优于数字离轴全息系统。这一研究为数字全息系统的设计和操作提供了一定的理论和实验指导。     

Tukey窗切趾全息图用于粒子场在焦位置测量的实验研究

提出采用能量透射率较大、频谱旁瓣峰值和旁瓣衰减斜率较小的Tukey窗对粒子场数字全息图进行切趾处理.分析了在焦位置测量和Tukey窗切趾粒子场数字全息图的原理.实验记录了附着于玻璃板表面的微小单层粒子场的数字全息图,采用Tukey窗对其切趾后进行数值再现.实验结果表明,全息图切趾后的再现像中已不存在黑白相间的干涉条纹,衬比度增强,再现粒子像更清晰,处于边缘区域的再现粒子像几乎被切趾孔径所淹没;随着窗函数切趾参量的逐渐增大,可更准确地确定单层粒子场的在焦位置,提高粒子场在焦位置的测量精度.     

Planktonic response to light as a pollution indicator

Ecological monitoring requires sensitive and effective approaches to detecting polluting substances. One such approach involves tracking the behavioral responses of plankton that is initially adapted to normal habitat conditions. Zooplankton such as Daphnia are filter feeders that are highly sensitive to pollution. We describe how a submersible holographic camera with additional attracting lighting (at a wavelength of 532 nm) can be used to track changes of Daphnia response to light for a number of pollutants, including potassium dichromate and crude oil. Our laboratory experiments showed that the sensitivity of this method of bioanalysis is comparable to standard laboratory methods, but has the additional advantage that it can be used in real time in lakes and other water areas, and hence is more versatile than standard methods.     

Comprehensive performance analysis of objective quality metrics for digital holography

Objective quality assessment of digital holograms has proven to be a challenging task. While prediction of perceptual quality of the recorded 3D content from the holographic wavefield is an open problem; perceptual quality assessment from content after rendering, requires a time-consuming rendering step and a multitude of possible viewports. In this research, we use 96 Fourier holograms of the recently released HoloDB database to evaluate the performance of well-known and state-of-the-art image quality metrics on digital holograms. We compare the reference holograms with their distorted versions: (i) before rendering on the real and imaginary parts of the quantized complex-wavefield, (ii) after converting Fourier to Fresnel holograms, (iii) after rendering, on the quantized amplitude of the reconstructed data, and (iv) after subsequently removing speckle noise using a Wiener filter. For every experimental track, the quality metric predictions are compared to the Mean Opinion Scores (MOS) gathered on a 2D screen, light field display and a holographic display. Additionally, a statistical analysis of the results and a discussion on the performance of the metrics are presented. The tests demonstrate that while for each test track a few quality metrics present a highly correlated performance compared to the multiple sets of available MOS, none of them demonstrates a consistently high-performance across all four test-tracks.