Three-dimensional display using computer-generated hologram based on virtual optics

The technique of using computer-generated hologram (CGH) for 2-D and 3-D display based on virtual optics was researched widely. A new way, modified peak signal to noise ratio (PSNR) method was used to assess 3-D image quality reconstructed by CGH, and an iterative arithmetic was proposed to synthesize CGH perfectly. Furthermore, in the paper a novel way to encrypt 3-D information was proposed. Simulation experiments showed that CGH was an effective encryption technique, and Modified PSNR was a proper definite quantity analysis method for 3-D imaging.     

双近贴式X射线像增强器成像系统的三维噪音测量及其分析技术

针对基于双近贴式X射线像增强器的射线成像系统,提出了该系统的三维噪音测试及分析方法.分析了各噪音因子的含义,用三维曲线描绘出空间域和时间域噪音的分布情况,结合数字图像处理技术,测量了双近贴式X射线像增强器成像系统在微焦斑射线源四种照射条件下的三维噪音,并对其结果进行分析.分析表明,其结果与双近贴式X射线像增强器成像系统实际性能相吻合.     

双近贴式X射线像增强器成像系统的三维噪音测量及其分析技术

针对基于双近贴式X射线像增强器的射线成像系统,提出了该系统的三维噪音测试及分析方法.分析了各噪音因子的含义,用三维曲线描绘出空间域和时间域噪音的分布情况,结合数字图像处理技术,测量了双近贴式X射线像增强器成像系统在微焦斑射线源四种照射条件下的三维噪音,并对其结果进行分析.分析表明,其结果与双近贴式X射线像增强器成像系统实际性能相吻合.     

Passive interferometric 3-D imaging and incoherence gating

This paper proposes interferometric 3-D imaging based on retrieving the space variant cross-spectral density. The cross-spectral density across an arbitrary transverse plane can be retrieved by using the propagation law described in the Fourier domain. The 3-D intensity distribution is reconstructed from a series of the cross-spectral densities across planes within the slab geometry considered. Results of an experiment conducted by incorporating two point sources are also reported. The point spread function of the proposed interferometric imaging system, and its similarity to an ordinary imaging system are discussed. To detect spatially incoherent sources, we also propose an incoherence gating method based on the present interferometric imaging technique. The second-order differential of the series of retrieved cross-spectral densities with respect to a two-point separation enable us to estimate field correlations over the 3-D field, and locations of primary sources are clearly determined.     

An improved 3-D Look--Locker imaging method for T(1) parameter estimation

The 3-D Look-Locker (LL) imaging method has been shown to be a highly efficient and accurate method for the volumetric mapping of the spin lattice relaxation time T(1). However, conventional 3-D LL imaging schemes are typically limited to small tip angle RF pulses (5 degrees ), thereby improving the SNR and the accuracy of the method. In phantom studies, a mean T(1) measurement accuracy of less than 2% (0.2-3.1%) using a tip angle of 10 degrees was obtained for a range of T(1) from approximately 300 to 1,700 ms with a measurement time increase of only 15%. This accuracy compares favorably with the conventional 3-D LL method that provided an accuracy between 2.2% and 7.3% using a 5 degrees flip angle.     

一种改进型视角投影图像彩色计算全息术的三维重构算法

本文提出了一种利用三维景物的二维视角投影图像合成计算全息图,并重构出彩色再现三维影像的方法.该方法基于利用视角投影图像获取景物的三维傅里叶频谱的理论,采用电荷耦合器件记录三维景物在白光照明条件下横、纵两正交方向的一系列视角投影图像,并利用这些视角投影图像合成计算全息图,从而重构出三维再现像.通过采用在频谱面上的容余采样方法,提高了图像频谱信息的利用率,通过实验论证,证明了该方法的可行性.利用该方法使得视角投影图像的记录过程更加简单,节省了采样时间,提高了程序运行速度|能够在利用同等数量的视角投影图像的条件下,提高合成全息图的质量,使得重构的彩色再现三维影像更加清晰.     

基于高斯拟合的条纹管成像激光雷达目标重构

为得到更为精细的三维重构,提出一种基于信赖域法高斯拟合的峰值探测法,对每帧图像单时间通道的回波进行高斯建模,建模结果可有效减小噪声干扰,具有唯一峰值,该结果作为新的回波波形,再对其进行峰值探测,并基于空中目标实验数据对本文方法进行验证.实验结果表明,基于高斯拟合的峰值探测法可将特征数据的提取误差降至10%以内;利用该方法提取特征数据进行目标三维重构,可实现探测深度方向上最小30cm的空间分辨力,提高了条纹管激光雷达的三维成像精度.     

Analyse du codage de l'information en tomographie longitudinale a haute resolution

Using a 3-D Fourier analysis, we investigate the nature of the informations contained in the high resolution motion pinhole recordings. We show that these images can be interpreted as parallel projections of a distorted 3-D emitting object. Thus, the use of the 3-D central slice theorem and the circular motion of the pinhole show that a 3-D Fourier region remains unexplored. Such a fact leads to a notable degradation of objects containing only very low spatial frequencies. But, in other cases, this degradation is generally less important (heart imaging for instance) and the improvement in resolution of this method proves to be appreciable when analysing local defects of fixation in nuclear medicine.     

位错点阵投影的三维数字成像

提出一种基于位错点阵投影的三维数字成像方法。该方法以二维点阵结构光顺序照明参考平面和被测物体表面,通过分析分别投影在参考平面和物体上的点阵的成像过程,建立投射在参考平面和被测物体表面上的点阵中同一点在成像面上横向位置错动与被测物体深度之间的数学模型。依据此模型,通过计算相对应点在成像平面上的横向位移。可计算出物体的深度图像。二维点阵可以在垂直于光轴的平面内做横向和纵向的两维移动,以填补由于离散而丢失的其他空间点的深度信息,获得高空间分辨率。实验验证了该方法的可行性,此方法对于拓扑复杂的表面和大梯度表面有较强的适应性。     

红外成像系统NETD参数测试算法及应用研究

噪声等效温差(NETD)是表征红外成像系统灵敏度的关键参数,也是评估红外成像系统性能的重要参数之一,应用广泛。通过对红外成像系统3D噪声、信号传递函数(SiTF)、NETD等参数测试方法、算法和流程研究,给出一种基于视频文件的3D噪声离线对比测试方法和一种SiTF线性区自动判断计算斜率算法,在此基础上针对某型技术保障装备国产化光电检测平台开发了配套应用软件功能模块。实现了通过计算单位均方根噪声所对应的SiTF斜率值,分析得出系统NETD参数值的功能。以某型热像仪为被测对象,开展了测试结果重复性和一致性试验,并与美国Optikos公司I-SITE红外整机测试系统进行了对比测试。实验结果表明开发的NETD参数测试功能模块测试精度和重复性满足设计要求,具有较高实用价值,已进行了工程应用。     

使用计算全息进行三维信息加密的方法研究

全息加密技术作为一种特殊的加密方法被广泛应用于信息加密和防伪等领域。在全息加密过程中,光波的波长、记录距离和入射角度等参数用做加密密钥和解密密钥被人们深入研究,但所加密的信息几乎都是二维信息。利用一种基于虚拟光学的对三维信息进行加密的方法,将三维物体的大小作为一个新的密钥被引入安全全息加密算法,其安全性能得到了极大提高;在此基础上提出了对再现三维图像进行客观评价的方法,即修正峰值信噪比法(PSNR,PeakSignal-to-Noise Ratio)。模拟实验证明,计算全息方法(CGH,Computer-Generated Hologram)作为一种对三维信息进行加密的方法是可行的,修正PSNR法对再现三维图像的质量进行定量分析是有效的。     

Integral three-dimensional imaging with digital reconstruction

A computed three-dimensional (3-D) display system based on integral imaging is presented. The 3-D image is reconstructed by numerical processing of an optically observed image array formed by a microlens array. The algorithm for reconstructing 3-D images is robust, and it enables us to obtain the images viewed from arbitrary directions. This computer-based image retrieval makes it possible to improve qualities of the image such as contrast, brightness, and resolution by numerical techniques. Also, this method eliminates the need for special purpose optical equipment such as high-quality liquid-crystal display and micro-optics components to display the 3-D images. We present experimental results of 3-D image reconstruction to test and verify the performance of the algorithms and the imaging system.     

自聚焦透镜的三维相干成像特性分析

运用傅里叶光学方法，分析并推导了自聚焦透镜的三维相干成像公式。研究表明，虽然自聚焦透镜中介质折射率是径向渐变折射率分布，不同于薄透镜中的均匀分布，但是由于它的三维相干成像性质却类似于薄透镜，从而使自聚焦透镜可以在成像和光学信息处理系统中有效地代替薄透镜，实现光学系统的微型化。     

Rapid Frequency-Domain FLIM Spinning Disk Confocal Microscope: Lifetime Resolution,Image Improvement and Wavelet Analysis

A spinning disk confocal attachment is added to a full-field real-time frequency-domain fluorescence lifetime-resolved imaging microscope (FLIM). This provides confocal 3-D imaging while retaining all the characteristics of the normal 2-D FLIM. The spinning disk arrangement allows us to retain the speed of the normal 2-D full field FLIM while gaining true 3-D resolution. We also introduce the use of wavelet image transformations into the FLIM analysis. Wavelets prove useful for selecting objects according to their morphology, denoising and background subtraction. The performance of the instrument and the analysis routines are tested with quantitative physical samples and examples are presented with complex biological samples.     

A miniature high resolution 3-D imaging sonar

This paper discusses the design and development of a miniature, high resolution 3-D imaging sonar. The design utilizes frequency steered phased arrays (FSPA) technology. FSPAs present a small, low-power solution to the problem of underwater imaging sonars. The technology provides a method to build sonars with a large number of beams without the proportional power, circuitry and processing complexity. The design differs from previous methods in that the array elements are manufactured from a monolithic material. With this technique the arrays are flat and considerably smaller element dimensions are achievable which allows for higher frequency ranges and smaller array sizes. In the current frequency range, the demonstrated array has ultra high image resolution (1″ range × 1° azimuth × 1° elevation) and small size (<3″ × 3″). The design of the FSPA utilizes the phasing-induced frequency-dependent directionality of a linear phased array to produce multiple beams in a forward sector. The FSPA requires only two hardware channels per array and can be arranged in single and multiple array configurations that deliver wide sector 2-D images. 3-D images can be obtained by scanning the array in a direction perpendicular to the 2-D image field and applying suitable image processing to the multiple scanned 2-D images. This paper introduces the 3-D FSPA concept, theory and design methodology. Finally, results from a prototype array are presented and discussed.     

Visualization of three-dimensional temperature distributions in a large-scale furnace via regularized reconstruction from radiative energy images: numerical studies

In this paper, the possibility of visualization of three-dimensional (3-D) temperature distributions in large-scale boiler furnaces from radiative energy images captured by multiple charge-coupled device (CCD) cameras mounted around the furnace is studied numerically. For the calculation of the radiative energy image formation, a fast algorithm proposed by the authors for pinhole imaging is used in this paper, which is based on the Monte Carlo method and combined with a concept of angular factor effective for image formation. This algorithm is applicable for the emitting, absorbing, and isotropic scattering medium. For the inversion of the 3-D temperature distributions which is an ill-posed problem, a modified Tikhonov regularization method is improved, where the finite difference regularizer is defined and can be used in 3-D cases, and the optimal regularization parameter is suggested to be selected by using a post-treatment method. For a 3-D unimodal temperature distribution, the numerical simulation results show that the reconstruction errors for the 3-D temperature distribution can be maintained at levels similar to the measurement error and the visualization quality of the temperature distribution is satisfactory. For a kind of bimodal temperature distribution, the reconstruction errors are higher than those for the unimodal distribution, but the bimodal feature of the temperature distribution can also be reproduced clearly.     

光纤型光学相干层析成像系统的研制

光学相干层析(OCT)成像技术是一新近发展的高分辨力生物医学成像手段,能非侵入性地对活体内部的结构与生理功能进行可视化观察。采用宽带近红外光源,基于迈克耳孙干涉原理和外差探测方法,建立了单模光纤型光学相干层析成像系统,相干地提取从生物体内部返回的深度分辨的弹性散射光信息,并依此构筑了自然状态下活体组织的二维光学相干层析成像图像和三维光学相干层析成像图像。光纤化设计的光学相干层析成像系统紧凑、灵活,便于与光纤导管、内窥镜和其它成像装置的有机结合,以拓展其观察范围和应用领域。     

基于遗传算法的二维随机型稀疏阵列的优化研究

为了解决二维相控阵列及与之匹配的三维超声成像系统过于复杂的问题,提出了一种基于遗传算法的随机型稀疏阵列的优化设计方法。在这种方法中,首先根据横向分辨率的要求确定参考阵列的尺寸及加权分布,然后根据对比分辨率的要求确定稀疏阵列相对于参考阵列的稀疏率,最后利用遗传算法优化确定阵元的分布形式。通过连续波理论和基于空间冲激响应的脉冲场模型对这种稀疏阵列的声学特性进行了分析,分析结果表明,优化设计的随机型稀疏阵列具有良好的特性,它与参考阵列有几乎相等的主瓣宽度,而且不产生栅瓣,虽然其旁瓣高度与参考阵列相比略有提升,但经遗传算法优化后仍能满足高质量成像的要求。     

碘化亚铜配位聚合物的单光子和双光子激发发光

利用两种半柔性的π-不饱和双吡啶端基配体与CuI配位,分别通过结构转化法和原位组装法,得到两种具有{[CuIL]·solvents}_n结构通式的二维和三维碘化亚铜配位聚合物,分别命名为Cu-3和Cu-4。利用X射线单晶衍射、X射线粉末衍射和元素分析等表征方法确定了Cu-3和Cu-4的结构信息。研究这两种配位聚合物的光物理性能发现,用紫外光激发时,Cu-3和Cu-4均表现出单一发射峰,最大波长分别为513 nm的蓝绿光和555 nm的黄色光,归属于卤素到配体的电荷转移(³XLCT)。同时,这两种配位聚合物均表现出双光子激发发光性质,有望应用于生物成像领域。     

MRI inter-slice reconstruction using super-resolution

MRI reconstruction using super-resolution is presented and shown to improve spatial resolution in cases when spatially-selective RF pulses are used for localization. In 2-D multislice MRI, the resolution in the slice direction is often lower than the in-plane resolution. For certain diagnostic imaging applications, isotropic resolution is necessary but true 3-D acquisition methods are not practical. In this case, if the imaging volume is acquired two or more times, with small spatial shifts between acquisitions, combination of the data sets using an iterative super-resolution algorithm gives improved resolution and better edge definition in the slice-select direction. Resolution augmentation in MRI is important for visualization and early diagnosis. The method also improves the signal-to-noise efficiency of the data acquisition.