Steganography and authentication in image sharing without parity bits

Recently, a polynomial-based (k, n) steganography and authenticated image sharing (SAIS) scheme was proposed to share a secret image into n stego-images. At the same time, one can reconstruct a secret image with any k or more than k stego-images, but one cannot obtain any information about the secret from fewer than k stego-images. The beauty of a (k, n)-SAIS scheme is that it provides the threshold property (i.e., k is the threshold value), the steganography (i.e., stego-images look like cover images), and authentication (i.e., detection of manipulated stego-images). All existing SAIS schemes require parity bits for authentication. In this paper, we present a novel approach without needing parity bits. In addition, our (k, n)-SAIS scheme provides better visual quality and has higher detection ratio with respect to all previous (k, n)-SAIS schemes.     

导板光互连光斑位置偏移的研究

随着人们对信息处理与交换速度和容量提出的更高的要求,出现了光互连．它具有并行处理、传播速度快、信息量大、空间频带宽、串音小和能量损耗低等优点,因此它在光计算机和信息处理领域中成为越来越吸引人的课题［１～４］提出光电结合的计算机系统．实现光－电混合计算．ＳａｕｅｒＦ提出了将电子元件组成的电路板安装在光导板上的方法［５,６］．每个电路板除了包括计算机本身要求的功能外,还装上发射信号的光源和接收信号的探测器,借助全息元件的耦合,以光导板作为光信息交换的通道．这种互连方式传输信息,结合光电优点,利用Ｂｒ…     

URA编码孔径的层析成像

URA编码孔径成像是X射线成像的一项新技术.它不但提高了信噪比,而且具有层析分辨能力.本文详细论述了URA编码孔径的层析成像原理,并提供了一种改善层析成像质量的叠代方法.并应用迭代方法成功地进行了计算机模拟实验.     

Optimization of microvia-technology using excimer laser for build-up layer application in microelectronics

In interconnection microelectronics microvias play a key role in the manufacture of high-density circuitry for use in electronic systems such as portable, smart sensors and computing applications. In the current work an excimer laser is used and microvias in the dielectric of the build-up layer are generated with the mask imaging method. Different laser parameters (demagnification factor, energy transmission percentage, fluence) are optimised in order to obtain microvias with different diameters, taper angle and aspect ratio. With electrochemical Cu-deposition interconnections between the upper and the underlying circuitry are realised. A nearly uniform thickness of the plated copper is obtained, and quality of the plating is assessed by means of the degree of delamination of the electrochemically deposited copper.     

多光子皮肤成像技术及其应用

多光子成像技术是一种层析能力好、信噪比高的新型光学成像技术。在皮肤光学三维检测中,多光子技术已经应用于无创在体成像,且已得到产业化开发。本文将首先介绍多光子皮肤检测系统的若干核心技术,即双光子自发荧光技术、二次谐波成像技术、荧光寿命成像技术、相干反斯托克斯-拉曼成像技术等,然后简要介绍多光子成像系统在皮肤疾病成像检测上的应用,最后分析该系统的优势和未来可能的发展趋势。     

3种主动合成孔径成像技术极限探测能力的分析与比较

为了深入研究可行的中高轨成像技术,本文从探测能力角度(用最低发射激光功率表示)深入分析和比较3种主动干涉合成孔径成像技术——傅立叶望远镜(又称为相干场成像或条纹场扫描成像)、成像相关术(又称为强度相关成像)和剪切光束成像。本文利用光电倍增管的信噪比模型和激光作用距离方程,较为细致地分析每种技术在满足单次信噪比(SNR=5)条件下的极限探测能力。通过仿真分析得出:傅立叶望远镜、成像相关术和剪切光束成像所需的最低单光束单脉冲能量分别为11. 4 J、0. 73 MJ和3. 1 MJ。最终得出傅立叶望远镜是上述3种主动成像技术中在目前技术水平下最适合中高轨目标(约36 000 km)高分辨成像的可用技术的结论。     

太赫兹远距离快速扫描成像系统的设计

在太赫兹成像技术研究中,分辨率、成像时间和距离是非常关键的参数指标,为了推动太赫兹成像技术的实用化,特别是提高对隐藏危险物品的远距离快速预警检测能力,提出被动式远距离太赫兹快速扫描成像系统。该系统采用单个太赫兹探测器和光机扫描相结合的方式。扫描子系统中,将六面体转镜置于离轴三反镜系统的平行光路中,使扫描范围从广泛研究中采用的物空间转换到像空间有效缩小了扫描区域,缩短了成像时间。本套被动式扫描成像系统主要参数:探测器频率0.34 THz,成像距离10 m,视场1.51.5,成像分辨率3 cm,成像时间1 s。     

Optoelectronic array interconnections

Two-dimensional parallel optoelectronic links are proposed for interconnections between electronic boards. Experiments were performed with LED-arrays and laserdiodes as the light transmitter, multimode fibre-arrays and imaging systems for light guiding and a CMOS opto-ASIC as highly sensitive light-receiver (detection limit is 1 fJ bit^–1 at a bit error rate of less than 10^–9). In the experiment each channel has a data rate of 10 Mbits^–1, the system is designed for 128 parallel channels occupying an area of less than 1 cm² and thus providing an overall throughput of more than 1 Gbits^–1. The applications are connections between CPUs and shared memories within a multiprocessor system.     

X‐ray grating interferometer for biomedical imaging applications at Shanghai Synchrotron Radiation Facility

An X‐ray grating interferometer was installed at the BL13W beamline of Shanghai Synchrotron Radiation Facility (SSRF) for biomedical imaging applications. Compared with imaging results from conventional absorption‐based micro‐computed tomography, this set‐up has shown much better soft tissue imaging capability. In particular, using the set‐up, the carotid artery and the carotid vein in a formalin‐fixed mouse can be visualized in situ without contrast agents, paving the way for future applications in cancer angiography studies. The overall results have demonstrated the broad prospects of the existing set‐up for biomedical imaging applications at SSRF.     

A flexible 9-channel coil array for fast 3D MR thermometry in MR-guided high-intensity focused ultrasound (HIFU) studies on rabbits at 3 T

Signal-to-noise ratio (SNR) is a critical factor in MR-guided high-intensity focused ultrasound (HIFU) for local heating, which can affect the accuracy of temperature measurement. In order to achieve high SNR and higher temporal resolution, dedicated coil arrays for MR-guided HIFU applications need to be developed. In this work, a flexible 9-channel coil array was designed, and constructed at 3 T to achieve fast temperature mapping for MR-guided HIFU applications on rabbit leg muscle. Coil performance was evaluated for SNR, and parallel imaging capability by in-vivo studies. Compared to a commercially available 4-channel flexible coil array, the dedicated 9-channel coil array has a much higher SNR, with at least a 2.6-fold increment in the region of interest (ROI). The inverse g-factors maps demonstrated that the dedicated 9-channel coil array has a better parallel imaging capability than the Flex Small 4. With accelerations normal to the array direction, both coil arrays showed much higher g-factors than those of accelerations along the array direction. Room temperature mapping was implemented to evaluate the temperature measurement accuracy by in-vivo experiments. The precisions of the 9-channel coil, ±0.18 °C for un-acceleration and ± 0.56 °C for acceleration at R = 2 × 2, both improved by an order of magnitude than these of the 4-channel coil, which were ± 1.45 °C for un-acceleration and ± 3.52 °C for acceleration at R = 2 × 2. In the fast temperature imaging on the rabbit leg muscle with heating, a high temporal resolution of 3.3 s with a temperature measurement precision of ±0.56 °C has been achieved using the dedicated 9-channel coil. This study demonstrates that the dedicated 9-channel coil array for rabbit leg imaging provides improved performance in SNR, parallel imaging capability, and the accuracy of temperature measurement compared to a commercial 4-channel coil, and it also achieves fast temperature mapping in practical MR-guided HIFU applications.     

Optical adaptive neural networks with a ground glass for global random interconnections and local gain controls

TAG (training by adaptive gain) is a new adaptive neural network model for large-scale optical implementations. For single-layer neural networks withN input andM output neurons, the TAG model contains two different types of interconnections, i.e.MN global fixed interconnections and (N+M) adaptive gain controls. The training algorithm is based on gradient descent and error back-propagation, and is easily extensible to multilayer and/or higher-order architectures. For large-scale electrooptic implementation, the fixed global interconnections may be implemented by multifacet hologram, volume hologram or ground glass, and the adaptive gains by spatial light modulators (SLMs). The ground glass is more advantageous for random interconnections, with much higher diffraction efficiency and interconnection density. Both feed-forward signal and error back-propagation paths are implemented by a single ground glass, and adaptive learning has been demonstrated for heteroassociative memory and classifier.     

A direct modulated optical link for MRI RF receive coil interconnection

Optical glass fiber is a promising alternative to traditional coaxial cables for MRI RF receive coil interconnection to avoid any crosstalk and electromagnetic interference between multiple channels. A direct modulated optical link is proposed for MRI coil interconnection in this paper. The link performances of power gain, frequency response and dynamic range are measured. Phantom and in vivo human head images have been demonstrated by the connection of this direct modulated optical link to a head coil on a 0.3T MRI scanner for the first time. Comparable image qualities to coaxial cable link verify the feasibility of using the optical link for imaging with minor modification on the existing scanners. This optical link could also be easily extended for multi-channel array interconnections at high field of 1.5 T.     

Flexible calibration technique for fringe-projection-based three-dimensional imaging

Fringe projection profilometry (FPP) has evolved dramatically, with many highly demanded features for three-dimensional (3D) imaging, such as high accuracy, easy implementation, and capability of measuring multiple objects with complex shapes. A vital component for an FPP-based 3D imaging system is the calibration process. The existing calibration methods lack the ability to be flexibly compatible with various scales of the field of imaging. In this Letter, a technique to cope with this issue is presented; it employs a checkerboard along with practical considerations to ensure reliable and accurate calibration. The validity and practicality of the technique are verified by experiments.     

光谱分辨率可调的新型干涉成像光谱技术研究

针对色散型和静态干涉型成像光谱仪光谱分辨率固定、系统效能得不到充分发挥等问题,提出了一种光谱分辨率可调的静态双折射干涉成像光谱技术.该技术的创新点之一在于,仪器的光谱分辨能力可调,且调节范围较宽.对于不同的探测目标,利用这一技术,只获取有用的光谱数据,既能满足多目标、多任务光谱图像探测的需要,又可大幅减少对存储空间和通信带宽的占用,有效缩短数据处理时间,提高系统信噪比,从而使仪器总体性能达到最优.本文给出了新技术的具体实现方案及理论模型,对核心元件—横向剪切量可调的新型双Wollaston平行平板分束器进行了光线追迹,给出了其横向剪切量的精确理论计算公式,深入分析了其分光及横向剪切量调节原理.在此基础上,研究了新技术的光谱分辨率调节特性,给出了其光谱调节范围,并对其光谱调节原理进行了实验验证.     

A multilevel nano-scale interconnection RLC delay model

Based on the multilevel interconnections temperature distribution model and the RLC interconnection delay model of the integrate circuit,this paper proposes a multilevel nano-scale interconnection RLC delay model with the method of numerical analysis,the proposed analytical model has summed up the influence of the configuration of multilevel interconnections,the via heat transfer and self-heating effect on the interconnection delay,which is closer to the actual situation.Delay simulation results show that the proposed model has high precision within 5% errors for global interconnections based on the 65 nm CMOS interconnection and material parameter,which can be applied in nanometer CMOS system chip computer-aided design.     

Near-infrared laser scanning confocal microscopy and its application in bioimaging

Near-infrared (NIR) fluorescence imaging is an important imaging technology in deep-tissue biomedical imaging and related researches, due to the low absorption and scattering of NIR excitation and/or emission in biological tissues. Laser scanning confocal microscopy (LSCM) plays a significant role in the family of fluorescence microscopy. Due to the introduction of pinhole, it can provide images with optical sectioning, high signal-to-noise ratio and better spatial resolution. In this study, in order to combine the advantages of these two techniques, we set up a fluorescence microscopic imaging system, which can be named as NIR-LSCM. The system was based on a commercially available confocal microscope, utilizing a NIR laser for excitation and a NIR sensitive detector for signal collection. In addition, NIR fluorescent nanoparticles (NPs) were prepared, and utilized for fluorescence imaging of the ear and brain of living mice based on the NIR-LSCM system. The structure of blood vessels at certain depth could be visualized clearly, because of the high-resolution and large-depth imaging capability of NIR-LSCM.     

Non-invasive investigation of art paintings by terahertz imaging

Terahertz electromagnetic waves propose attractive features such as non-invasive and non-destructive analysis, transparency and good penetration depth through various materials, low scattering and broad spectral bandwidth. In this paper, we demonstrate the capability of terahertz imaging for the investigation of art paintings. The imaging system is able to reveal buried layer information such as a graphite handmade sketch covered by several layers of painting. In addition, taking advantage of the pulsed terahertz emission, we show that it is also possible to evaluate the variations of the painting thickness.     

基于超快超声多普勒的三维脑损伤成像方法研究

三维超声微血管成像可直观呈现血流信息,对于脑血管疾病诊断和治疗具有重要意义。本文旨在将超快超声成像技术、超快超声功率多普勒技术和机械扫描相结合,实现脑血管三维成像和脑缺血区域评价。通过工程实现,完成了可同步控制微型线性位移平台移动和超声阵列超快发射、高速采集与压缩存储的三维扫描数据采集序列与系统。利用GPU并行运算,高效实现了超声图像波束合成方法,对原始射频超声数据完成重建。进而,基于SVD杂波滤除技术,从重建三维超声数据中提取了脑部的动态小血管信号,并获得了各切面的功率多普勒成像和冠状面彩色多普勒超声小血管成像。最后,采用体素方法对三维脑血管进行重建。大鼠在体实验结果表明,该成像系统可用于三维脑血管网络在体成像,以及脑血管损伤区域定位与量化评价。本工作对脑病检测技术发展与诊断方法研究具有一定的借鉴意义。此外,相关检测系统和成像算法具有一定普适性,对其他富含微血流血管的组织检测也有一定的参考价值。     

基于X光微点源的半影成像技术

基于X光微点源装置,从实验角度验证了半影成像的原理。利用针孔成像,直接测量了微点源源区图像;给出了半影孔成像、半影锥成像和环孔成像原理,以及在微点源的半影成像结果和维纳滤波重建结果。从实验结果可知:半影锥成像具有与半影孔成像相同的诊断能力,两种方法的重建图像尺寸与源尺寸一致;环孔成像的诊断能力更好,重建图像的尺寸和形状更接近源图像。     

Fast voice-coil scanning optical-resolution photoacoustic microscopy

We developed a photoacoustic imaging system that has real-time imaging capability with optical resolution. The imaging system is capable of scanning at 20 Hz over a 9 mm range and up to 40 Hz over a 1 mm scanning range. A focused laser beam provides a lateral resolution of 3.4 μm as measured in an optically nonscattering medium. Flows of micrometer-sized carbon particles or whole blood in a silicone tube and individual red blood cells (RBCs) in mouse ear capillaries were also imaged in real time, demonstrating the capability to image highly dynamic processes in vivo at a micrometer-scale resolution.