Real-Time Integral Imaging Based on Extremely High Resolution Video System

The authors discuss practical problems, focusing, and accuracy of lens arrays involved in constructing integral imaging systems. In general, it is recommended to set the focusing for the object during capture to infinity. The positional error of the elemental lens arrangement significantly affects the image quality when the image is reconstructed near the observer. An experimental system in consideration of the practical problems that uses an extremely high resolution video system is described. Some pictures obtained by the system show the specific characteristics of this spatial imaging type of system.     

激光三维成像技术及其主要应用

阐述了目前三维成像在其常见应用领域中的研究,主要致力于研究高分辨率三维成像系统。三维激光成像是一项可以应用于探测隐藏目标、地形测绘、构建虚拟环境、城市建模、目标识别等领域中的技术。在区域成像技术中,除了如立体视觉和结构化灯光等更常规的技术,实时三维传感也具有现实可操作性。当前三维激光成像技术已经发展到有能力提供厘米级波长的高分辨率三维成像,这将给许多领域提供方便,包括法律的实施和法医调查。与CCD和红外技术等传统的被动成像系统相比,激光成像技术不仅能提供强度和范围信息,还能穿透植被和窗户等特定情景元素。这意味着激光三维成像系统在目标识别与辨认等方面具备新的潜力。结果表明,激光三维成像系统可以在许多情况下得到应用。     

The fusion of different resolution SAR images

We explore the possibility of using different data sets relative to the same scene to obtain a better knowledge of the scene than the one obtained using only one data set. In particular we concentrate on the fusion of two different spatial resolution images, although the method we propose can be regarded as a method of more general interest. The fused image has the least mean square deviation from the finer resolution image, subject to the constraints imposed by the knowledge of the coarser resolution image. Fusion is obtained by solving a constrained quadratic highly parallelizable minimization problem. Explicit formulas for the solution of the minimization problem are given. The number of elementary operations required is proportional to the number of pixels of the finer resolution image. We test our method on a class of simulated images that reproduce some features of synthetic aperture radar (SAR) images. As an example we consider the problem of detection of point scatterers in a uniform background. The results obtained show that the information from the coarser resolution image can significantly improve the quality of the reconstructed scene obtained from the finer resolution image     

Random Projections Imaging With Extended Space-Bandwidth Product

We propose a novel approach to imaging that is not based on traditional optical imaging architecture. With the new approach, the image is reconstructed and visualized from random projections of the input object. The random projections are implemented within a single exposure by using a random phase mask which can be placed on a lens. For objects that have sparse representation in some known domain (e.g., Fourier or wavelet), the novel imaging systems have larger effective space - bandwidth product than conventional imaging systems. This implies, for example, that more object pixels may be reconstructed and visualized than the number of pixels of the image sensor. We present simulation results on the utility of the new approach. The proposed approach can have broad applications in efficient imaging capture, visualization, and display given ever increasing demands for larger and higher resolution images, faster image communications, and multidimensional image communications such as 3-D TV and display.     

红外点元探测器扫描成像方法研究

针对传统红外面阵探测器成像存在分辨率低、视场范围窄、非均匀性的问题,提出一种基于红外点元探测器的扫描成像方法。该方法首先利用微型电机驱动扫描镜依次获取物体表面的红外热斑,经光学镜头聚焦到红外点元探测器,进行光电转换;然后经信号处理板采集、处理后生成红外灰度图像;最后利用多阈值分割的伪彩色映射模型,将灰度图像转换成伪彩色图像。实验结果表明：红外点元探测器扫描成像方法能够实现红外场景的大视场、高分辨率成像,且点元探测器加工制造简单,价格低廉,有效突破了传统大面阵成像的高昂成本限制,更加有利于红外成像技术的推广和应用。     

Real time 3D visualization of intraoperative organ deformations using structured dictionary

Restricted visualization of the surgical field is one of the most critical challenges for minimally invasive surgery (MIS). Current intraoperative visualization systems are promising. However, they can hardly meet the requirements of high resolution and real time 3D visualization of the surgical scene to support the recognition of anatomic structures for safe MIS procedures. In this paper, we present a new approach for real time 3D visualization of organ deformations based on optical imaging patches with limited field-of-view and a single preoperative scan of magnetic resonance imaging (MRI) or computed tomography (CT). The idea for reconstruction is motivated by our empirical observation that the spherical harmonic coefficients corresponding to distorted surfaces of a given organ lie in lower dimensional subspaces in a structured dictionary that can be learned from a set of representative training surfaces. We provide both theoretical and practical designs for achieving these goals. Specifically, we discuss details about the selection of limited optical views and the registration of partial optical images with a single preoperative MRI/CT scan. The design proposed in this paper is evaluated with both finite element modeling data and ex vivo experiments. The ex vivo test is conducted on fresh porcine kidneys using 3D MRI scans with 1.2 mm resolution and a portable laser scanner with an accuracy of 0.13 mm. Results show that the proposed method achieves a sub-3 mm spatial resolution in terms of Hausdorff distance when using only one preoperative MRI scan and the optical patch from the single-sided view of the kidney. The reconstruction frame rate is between 10 frames/s and 39 frames/s depending on the complexity of the test model.     

Image reconstruction from multiple frames of sparse data

High-resolution image reconstruction from sparse data is an important problem in sensor array imaging (SAI). The reconstructed images from such a data are poorly resolved. However, there may exist possibilities of making multiple measurements, for example, collecting many frames of data in a dynamic scene situation where there is relative motion between the object and the receiver. We discuss here a method of reconstructing good-quality images from multiple frames of sparse data obtained from a simulated dynamic scene situation. This method, based on projection onto convex sets (POCS), not only restricts the solution set by satisfying the constraints in the multiple measurements but also reconstructs a high-resolution image.     

地基MIMO雷达快速成像算法研究

地基多输入多输出(Multiple-Input Multiple-Output, MIMO)成像雷达采用数字波束形成技术实现二维成像,具有成像速度快的技术优势。本文提出了一种适用于大景深、宽视角场景的地基MIMO雷达的快速二维成像算法。首先,根据MIMO雷达的阵列构型建立回波信号模型;其次,基于该模型补偿天线阵列近场空变性的相位中心近似(Phase Center Approximation, PCA)误差并进行数据重排,通过Kesytone变换校正距离徙动;然后,利用方位分块Dechirp处理实现方位向聚焦,实现MIMO雷达二维成像;最后利用MIMO雷达外场实验数据完成了算法验证。研究结果表明:在保证成像精度要求的情况下,该算法可以实现大景深、宽视角场景的高分辨快速成像,成像处理时间优于反向投影成像(Back Projection, BP)算法。      

自聚焦共焦光纤传感系统的相干传递函数

在弱物体近似下，运用傅立叶光学，从成像系统角度对自聚焦共焦传感技术进行了理论研究。首重分析了该技术测量样品纵深结构时图像的成像机理。由于光纤具有本征场的模式，对光的振幅和相位的响应是相干的，从而可用相干传递函数（CTF）描述系统性能。结果表明，系统相当于一复振幅线平移不变系统，具有低通特性和层析特性。     

A unified framework for multi-sensor HDR video reconstruction

One of the most successful approaches to modern high quality HDR-video capture is to use camera setups with multiple sensors imaging the scene through a common optical system. However, such systems pose several challenges for HDR reconstruction algorithms. Previous reconstruction techniques have considered debayering, denoising, resampling (alignment) and exposure fusion as separate problems. In contrast, in this paper we present a unifying approach, performing HDR assembly directly from raw sensor data. Our framework includes a camera noise model adapted to HDR video and an algorithm for spatially adaptive HDR reconstruction based on fitting of local polynomial approximations to observed sensor data. The method is easy to implement and allows reconstruction to an arbitrary resolution and output mapping. We present an implementation in CUDA and show real-time performance for an experimental 4 Mpixel multi-sensor HDR video system. We further show that our algorithm has clear advantages over existing methods, both in terms of flexibility and reconstruction quality.     

基于面阵CCD-TDI模式编码感知的高分辨率遥感计算成像

针对推扫式遥感成像,基于压缩感知(CS)理论,提出一种利用低密度探测器获取高分辨率遥感图像的新方法。在推扫过程中,采用可编码的行间转移面阵电荷耦合器件(CCD)并使其工作于时间延迟积分(TDI)模式,在随机曝光控制电路的控制下实现对场景信息的编码感知;通过计算成像,从感知的数据中重构出高分辨率遥感图像。这种基于CCD-TDI模式编码感知的高分辨率遥感计算成像方法,可以增强成像分辨率和提高输出图像信噪比。仿真结果验证了本文方法的有效性。     

Resolution of Near-Field Microwave Target Detection and Imaging by Using Flat LHM Lens

It is demonstrated in this paper that higher focusing resolution will be provided by flat left-handed metamaterial (LHM) lens if compared to convex dielectric lens and elliptical reflector focusing system. High-resolution near-field microwave target detection and imaging with flat LHM lens can be implemented by scanning the focal point of the flat LHM lens in the region under detection and screening directly the field intensity distribution of backscattered microwave refocused by the flat LHM lens. Numerical simulations demonstrate that sub-wavelength imaging resolution can be obtained by the proposed approach due to the sub-wavelength focusing resolution of flat LHM lens. Moreover, almost unique imaging resolution for the detection and imaging of target at different depths is also demonstrated. For practical LHM lenses, it is shown that the losses of LHM up to the order as reported in some LHM experiments will limit the sub-wavelength resolution of the proposed approach to an acceptable level.     

Three-dimensional holographic image sensing and Integral imaging display

In this paper, we propose three-dimensional (3-D) holographic sensing, and computational/optical 3-D integral imaging reconstruction. We demonstrate experimentally that through the integral imaging technique, it is possible to reconstruct a full 3-D scene which has been obtained by digital holograms. Three-dimensional color objects can also be displayed optically in 3-D without convergence-accommodation conflict using a microlens array, and a two-dimensional (2-D) display panel illuminated by incoherent light. The proposed approach takes advantages of high resolution holographic sensing and robust 3-D integral imaging visualization.     

Imaging with solid immersion lenses, spatial resolution, and applications

Solid immersion microscopy, similar to liquid immersion microscopy, extends the diffraction limit by filling the object space with a high refractive index material, such as glass (index of refraction n=1.5-2), sapphire (n/spl sim/1.8), and semiconductor materials (n/spl sim/3), which shrink the wavelength of light. But solid immersion technique can achieve significantly higher spatial resolution since the refractive indices of available solids can be much higher than those of liquids (n=1.3-1.5). Besides high spatial resolution, solid immersion microscopy also possesses all the good properties of far-field imaging, such as high transmission efficiency and parallel imaging capability, which make it outstanding among beyond-the-diffraction-limit optical imaging techniques. In this paper, we discuss, from an experimental point of view, the resolution limit of solid immersion microscopy and the implementation of such technique in various applications.     

A new fast method for the reconstruction of 2-D microwave images ofrotating objects

The problem of microwave imaging of rotating objects is approached from a digital signal processing point of view. Attention is focused on the reconstruction of the two-dimensional (2-D) image of an object obtained by processing complex samples of the continuous wave (CW) signal return received for different object aspect angles covering a 2pi total variation. The effects of a polar sampling of the Fourier transform (FT) of the target reflectivity function on the impulse response of the imaging system are analyzed. A criterion for the choice of the angular sampling interval in order to control the image blurring is given. Finally, a new and fast digital signal processing method for image reconstruction is proposed. This method reconstructs high resolution images of rotating targets illuminated by a CW electromagnetic signal or by a large bandwidth transmitted signal. This algorithm is suitable for processing wideband received signal of targets observed for a large variation of the viewing angle, so it is very attractive for the reconstruction of very high spatial resolution target images in SAR/ISAR systems. To show the performance of the method we finally present and discuss the results obtained by applying the proposed technique on simulated and experimental data.     

宽测绘带SAR成像的一种侧摆模式及其压缩感知处理方法

宽测绘带合成孔径雷达(SAR)采用了不同的信号录取方式及成像算法,但现有的ScanSAR和循序扫描体制(TOPSAR)往往会造成场景分辨率的整体下降。针对这一问题,该文采用一种新的侧摆模式进行宽幅场景成像。该模式通过距离向波束角度的变化,以损失部分积累时间为代价,得到宽幅场景的回波信号,继而采用稀疏算法在方位向实现降采样成像。仿真结果表明,在波束变化轨迹确定后,星载雷达侧摆模式下稀疏SAR成像可有效增加场景幅宽,同时确保场景中心区域的高分辨成像。     

Focus free terahertz reflection imaging and tomography with Bessel beams

A broadband terahertz (THz) reflection imaging system with high spatial resolution over a large depth of field is reported. A THz axicon lens producing a truncated THz Bessel beam with a linear focus exceeding 120 mm in length, and with the diameter of the central lobe less than 2 mm was used for imaging in a reflection geometry employing a pulsed THz time-domain spectrometer. With numerical post-processing, it was possible to reconstruct the three dimensional shape of the scanned object.     

一种超分辨距离多普勒成象方法

众所周知,距离多普勒成象雷达的距离分辨力和横向分辨力分别取决于发射信号的有效带宽和目标相对于雷达视线在相干处理区间内的转角,本文的研究工作旨在突破普通的FFT距离多普勒处理的限制,大大提高距离多普勒成象雷达的分辨能力,我们采用的方法是在进行付里叶重建之前用线性预测进行数据外推,用微波暗室试验数据进行转台成象的初步结果表明,这是一种改善距离多普勒成象雷达分辨能力的颇有前途的方法。     

采用双扫描平台技术的ArF浸液式光刻

在193nm光刻中,已证明水是一种适于浸液式光刻的液体。浸液式光刻提出了一种可将传统的光学光刻拓展到45nm节点,甚至到32nm节点的潜能。另外,利用现有的透镜,浸液式光刻的选择提出了根据实际的数值孔径和特征图形可增大50%及更大的焦深范围。讨论了采用浸液式光刻获得的成像结果和套刻结果。采用一个0.75数值孔径的ArF透镜,我们用双扫描平台技术(TWINSCANTM)组装一台浸液式扫描光刻机的原理型样机。最初的浸液式曝光实验数据证明了焦深的增加较大,同时以高扫描速度保持了图像的对比度。在初期引入的生产型浸液式光刻中,将采用一个0.85数值孔径的ArF透镜。该系统的分辨率将以大于0.5μm的焦深有效地支持65nm节点半导体器件的加工。这种系统初始的成像技术数据证实有效的增大了其焦深范围。