Diffractive elements for imaging optical systems

The problems and prospects of using diffractive elements with a sawtooth relief-phase microstructure in imaging optical systems are analyzed. Particular attention is paid to minimizing the adverse side effect of diffraction orders on the quality of the image formed by an optical system with a diffractive element due to the change-over from single-layer microstructures to structures containing several layers and reliefs. Requirements are formulated for the design parameters of the microstructure and operating conditions of diffractive elements in optical systems that ensure no visible halo caused by adverse diffraction orders. It is shown by a number of examples that the use of a diffractive element in a plastic-lens imaging optical system corrects chromatic aberrations and provides high resolution in the generated image.     

Magnetic resonance imaging-compatible tactile sensing device based on a piezoelectric array

Minimally invasive surgery is a widely used medical technique, one of the drawbacks of which is the loss of direct sense of touch during the operation. Palpation is the use of fingertips to explore and make fast assessments of tissue morphology. Although technologies are developed to equip minimally invasive surgery tools with haptic feedback capabilities, the majority focus on tissue stiffness profiling and tool-tissue interaction force measurement. For greatly increased diagnostic capability, a magnetic resonance imaging-compatible tactile sensor design is proposed, which allows minimally invasive surgery to be performed under image guidance, combining the strong capability of magnetic resonance imaging soft tissue and intuitive palpation. The sensing unit is based on a piezoelectric sensor methodology, which conforms to the stringent mechanical and electrical design requirements imposed by the magnetic resonance environment The sensor mechanical design and the device integration to a 0.2 Tesla open magnetic resonance imaging scanner are described, together with the device's magnetic resonance compatibility testing. Its design limitations and potential future improvements are also discussed. A tactile sensing unit based on a piezoelectric sensor principle is proposed, which is designed for magnetic resonance imaging guided interventions.     

Development of a solenoid RF coil for animal imaging in 3 T high-magnetic-field MRI

The purpose of this study was to develop a solenoid coil for use with small animals in a 3 Tesla horizontal magnetic resonance imaging (MRI) system, and to investigate image quality by examination of parameters such as signal-to-noise ratio (SNR) and Q-factor. A receiver solenoid coil was formed by winding three separate coils of copper tape around an acryl cylinder. The cylinder was supported at each end. A euthanized rat weighing 240 g was used as a subject animal for imaging. A cylindrical plastic tube containing a solution of 0.7 g/L CuSO(4) was used as a phantom. Measured SNRs were 985 in the phantom image 995 in the rat. The Q-factor was 89 in the phantom and 84 in the rat, in the loaded condition. The homogeneity of the radiofrequency (RF) field was good and the resolution of the image was sufficient to distinguish internal organs from one another in the abdomen of a rat. This study has demonstrated that a solenoid coil may be used to produce good quality images of small animals.     

Finite-element analysis for magnetic resonance image artifact evaluation

The static magnetic field of a magnetic resonance imaging scanner can be distorted by the presence of materials, perturbing the spatial encoding process in magnetic resonance imaging and often resulting in image artifacts. The relationship between the image artifact size and magnetic susceptibility of the material specimen is of interest to engineers for the design of devices that are to be compatible with the imaging volume of the scanner. In this study, a finite-element method was used to simulate the distorted magnetic field of samples with different susceptibilities. With the knowledge of the external- and self- magnetic field interactions, a Lorentz correction was applied to compute the magnetic field deviation. The simulated results were then validated by the corresponding experimental magnetic resonance images.     

Design of an active-passive device for human ankle movement during functional magnetic resonance imaging analysis

Functional magnetic resonance imaging analysis has made major strides in recent years, both because of the development of new scanners and owing to magnetic resonance compatible systems that make it possible to stimulate parts of the human body during analysis. The significant gains in our knowledge of the brain that can thus be achieved justify efforts to construct machines with control circuits suitable for this purpose. This paper presents a magnetic resonance compatible mechatronic device with electropneumatic control that can be used to move one or both feet during functional magnetic resonance imaging analysis of the cerebral motor zones. The system is innovative and original. The results obtained at the end of the investigation were good, and demonstrated that the design is feasible.     

仿复眼视觉系统的研究进展

复眼是昆虫重要的光感受器,由成千上万的小眼构成,具有大视野的动目标快速检测能力。仿复眼的多孔径系统在机器人视觉导航、大视角测量和全景成像等领域应用广泛。首先介绍了复眼的生物机理、成像特性及现有的大视场成像系统;其次介绍了微透镜阵列的仿复眼光学设计现状,分析了微透镜阵列的大视角与多景深的全景成像质量,指出目前曲面微透镜一体化制造存在的成像缺陷;最后提出结合曲面与平面微透镜阵列实现大视角、多景深分辨率的仿复眼系统的可行性。该成像系统不仅可以实现全景范围内的清晰成像,而且还具有全景范围内的目标位置估计能力。     

交变磁场下焊接缺陷磁光成像特征分析

研究焊接缺陷磁光成像检测方法,基于法拉第旋转效应,分析交变磁场下焊接缺陷磁光成像特征与漏磁场之间的关系.建立焊接缺陷的三维有限元模型,对不同类型和宽度的焊接缺陷漏磁场分布进行模拟,并在交变磁场激励下对不同焊接缺陷进行磁光成像无损检测试验,通过试验验证了焊接缺陷检测模型的有效性.研究结果表明,漏磁场分布与缺陷的类型和宽度...     

A magnetic-resonance-compatible limb-positioning device to facilitate magic angle experiments in vivo

Owing to their highly ordered structure, tendons and cartilage appear with low signal intensity when imaged using magnetic resonance imaging (MRI) scanners. A significant increase in signal can be observed when these structures are oriented at 55 degrees (termed the magic angle) with respect to the static field B0. There is a clear clinical importance in exploiting this effect as part of the diagnosis of injury. Experimental studies of this phenomenon have been made harder by the practical difficulties associated with tissue positioning and orientation in the confined environment of closed-bore scanners. An MRI-compatible mechatronic system has been developed, which is capable of positioning a number of limbs to a desired orientation inside the scanner, to be used as a diagnostic and research tool. It is actuated with a novel pneumatic motor consisting of a heavily geared-down air turbine, presenting high torques and good accuracy. The system is shown to be magnetic resonance compatible and the results of preliminary trials using the device to image the Achilles tendon of human volunteers at different orientations are presented. An increase of four fold to thirteen fold in signal intensity can be observed at the magic angle.     

车辆载体运动对摄像系统成像的影响分析

车辆栽体的随机振动影响摄像系统的成像质量,后续系统诸如目标跟踪和侦察预警系统的精度和稳定性.通过分析随机振动的特点及其产生的原因,可知随机振动受路面不平度、车辆载体类型和载体运动速度等因素的影响.根据采集的实际动态图像序列,分析摄像系统在不同影响因素下随机振动的特点.实验结果表明,车辆载体运动引起的图像帧间模糊和帧内模...     

Digital processing of images of extruded rubber profiles for process control MRI

Magnetic resonance imaging (MRI) is a powerful technique in materials science, in particular for the analysis of polymer and rubber materials. So far the use of this technique for quality control has not been fully explored mainly because of the prohibitive costs and maintenance associated with conventional MRI tomography systems. This constraint has been removed recently since robust and mobile desktop tomographs with permanent magnets have become available at reduced cost. In this work we apply an image processing chain algorithm to MR images of rubber profiles recorded with a desktop MRI scanner. Although the nominal spatial resolution of MR images is inherently lower than that of optical methods, we demonstrate that the digital resolution achieved after the image processing steps allows one to determine the spatial positions of the inner and outer contours with 50 μm precision. Using this information it is then possible to measure structural dimensions of the rubber profiles, such as wall thickness or internal voids, with precisions that are of the same order of magnitude as those observed with CT or camera imaging.     

Four-channel magnetic resonance imaging receiver using frequency domain multiplexing

An alternative technique that uses frequency domain multiplexing to acquire phased array magnetic resonance images is discussed in detail. The proposed method has advantages over traditional independent receiver chains in that it utilizes an analog-to-digital converter and a single-chip multicarrier receiver with high performance to reduce the size and cost of the phased array receiver system. A practical four-channel digital receiver using frequency domain multiplexing was implemented and verified on a home-built 0.3 T magnetic resonance imaging system. The experimental results confirmed that the cross talk between each channel was below -60 dB, the phase fluctuations were about 1 degrees , and there was no obvious signal-to-noise ratio degradation. It is demonstrated that the frequency domain multiplexing is a valuable and economical technique, particularly for array coil systems where the multichannel receiver is indispensable and dynamic range is not a critical problem.     

Design of X-ray digital imaging and data acquisition system

X-ray digital imaging technology is a new method of nondestructive testing. Non-film real time digital radiograph, which has high efficiency and low cost, especially the characteristics of digital image exchangeability and storage convenience, has become the development direction. Because the existing system has the disadvantage of low imaging quality and only being used at low X-ray energy, a high quality imaging system based on scientific CCD camera has been developed, which has high spatial solution and high contrast sensitivity and can be used both at high energy and low energy. This paper introduces the constitution of the system, and designs the relative circuits. The experimental results show that the system has the better imaging quality and wider adapting range for X-ray energy, can needs the requirements of measurement.     

Process Modeling of Ferrofluids Flow for Magnetic Targeting Drug Delivery

Among the proposed techniques for delivering drugs to specific sites within the human body, magnetic targeting drug delivery surpasses due to its non-invasive character and its high targeting efficiency. Although there have been some analyses theoretically for magnetic drug targeting, very few researchers have addressed the hydrodynamic models of magnetic fluids in the blood vessel of human body. This paper presents a mathematical model to describe the hydrodynamics of ferrofluids as drug carriers flowing in a blood vessel under the applied magnetic field. A 3D flow field of magnetic particles in a blood vessel model is numerically simulated in order to further understand clinical application of magnetic targeting drug delivery. Simulation results show that magnetic nanoparticles can be enriched in a target region depending on the applied magnetic field intensity. Magnetic resonance imaging conftrms the enrichment of ferrofluids in a desired body tissue of Sprague-Dawley rats. The simulation results coincide with those animal experiments. Results of the analysis provide the important information and can suggest strategies for improving delivery in favor of the clinical application.     

Resolution beyond the Rayleigh limit using beam displacement

Two fluorescence microscope systems which claim to achieve resolution beyond the Rayleigh limit have recently been described. These systems operate using two displaced beams focused on the sample and produce the image from the region of overlap. We describe an analogous system, which performs in a similar manner but does not rely on fluorescence. The imaging performance of these systems is analysed and we show that they all give improved resolution although, crucially, the optical bandwidth is not increased. These systems merely attenuate the lower spatial frequencies and, although such systems can be useful and operate in a manner analogous to pupil plane filters, it is important to appreciate that they do not offer true superresolution, contrary to the impression given in previous papers.     

Semi-automated imaging system to quantitate estrogen and progesterone receptor immunoreactivity in human breast cancer

A semi‐automated imaging system is described to quantitate estrogen and progesterone receptor immunoreactivity in human breast cancer. The system works for any conventional method of image acquisition using microscopic slides that have been processed for immunohistochemical analysis of the estrogen receptor and progesterone receptor. Estrogen receptor and progesterone receptor immunohistochemical staining produce colorimetric differences in nuclear staining that conventionally have been interpreted manually by pathologists and expressed as percentage of positive tumoral nuclei. The estrogen receptor and progesterone receptor status of human breast cancer represent important prognostic and predictive markers of human breast cancer that dictate therapeutic decisions but their subjective interpretation result in interobserver, intraobserver and fatigue variability. Subjective measurements are traditionally limited to a determination of percentage of tumoral nuclei that show positive immunoreactivity. To address these limitations, imaging algorithms utilizing both colorimetric (RGB) as well as intensity (gray scale) determinations were used to analyze pixels of the acquired image. Image acquisition utilized either scanner or microscope with attached digital or analogue camera capable of producing images with a resolution of 20 pixels /10 μ. Areas of each image were screened and the area of interest richest in tumour cells manually selected for image processing. Images were processed initially by JPG conversion of SVS scanned virtual slides or direct JPG photomicrograph capture. Following image acquisition, images were screened for quality, enhanced and processed. The algorithm‐based values for estrogen receptor and progesterone receptor percentage nuclear positivity both strongly correlated with the subjective measurements (intraclass correlation: 0.77; 95% confidence interval: 0.59, 0.95) yet exhibited no interobserver, intraobserver or fatigue variability. In addition the algorithms provided measurements of nuclear estrogen receptor and progesterone receptor staining intensity (mean, mode and median staining intensity of positive staining nuclei), parameters that subjective review could not assess. Other semi‐automated image analysis systems have been used to measure estrogen receptor and progesterone receptor immunoreactivity but these either have required proprietary hardware or have been based on luminosity differences alone. By contrast our algorithms were independent of proprietary hardware and were based on not just luminosity and colour but also many other imaging features including epithelial pattern recognition and nuclear morphology. These features provide a more accurate, versatile and robust imaging analysis platform that can be fully automated in the near future. Because of all these properties, our semi‐automated imaging system ‘adds value’ as a means of measuring these important nuclear biomarkers of human breast cancer.     

高质量X射线检测数字化成像及图像采集

X射线数字成像检测是工业无损检测的新技术.非胶片实时数字成像检测以其高效率、低成本,特别是数字图像的可交换性和存储方便等特点成为射线检测的发展趋势.通常使用的由射线像增强器、视频摄像机、图像采集卡和计算机组成的系统成像质量差且只能在低能X射线下使用,作者经过反复研究和实验,研制了基于单晶闪烁屏和科学级CCD相机的可用于高、低能X射线高分辨率、高对比灵敏度数字成像检测系统.介绍了整个检测系统的组成,设计了科学级制冷CCD相机、预处理电路、A/D转换电路、微机EPP方式快速数据采集电路和软件等.给出了某铝铸件(厚150mm)在加速器高能X射线下的成像结果.实验证明该系统比普通像增强器和视频相机组成的系统具有适应射线能量范围宽和成像质量好的优点(成像时间长一些).系统的空间分辨率大于3lp/mm, 检测物体50mm(等效钢厚)以上时,对比度灵敏度小于1%.     

一种基于复杂永磁体阵列的悬浮式振动能量采集器的精确模型及验证

为提高振动能量采集器的输出性能和工作频带，基于永磁体阵列和多自由度器件受到广泛关注。然而这类器件存在磁场分布复杂，动态特性难以模拟等问题。以一种基于复杂永磁体阵列的可调频磁悬浮振动能量采集器为研究对象，建立器件解析模型和有限元模型的联合分析模型，理论模型显示系统具有非线性振动特性，其动力学模型可简化为Duffing方程形式，并通过有限元模型简化了对非线性系统的分析。利用COMSOL有限元仿真研究器件磁场分布、非线性磁力特性，分析磁力和线圈位置对器件输出特性的影响。搭建测试平台对研制的可调频磁悬浮振动能量采集器进行试验表征，以验证联合分析模型。试验结果表明，在20～35 mm的固定磁铁间距离变化范围内，器件谐振频率变化范围为8.6～13.1 Hz，0.35g加速度下输出电压峰峰值为352.9～658.2 mV，联合分析模型与试验之间具有一致性。     

基于小发散角的投影式集成成像三维显示再现深度的拓展

针对集成成像裸眼三维显示技术受三维再现像再现深度的限制而无法实现大规模应用的问题,提出了一种基于小发散角的投影式集成成像三维再现深度的拓展方法.该方法利用投影式集成成像显示系统和一个辅助透镜来控制元素图像阵列中各像素点的发散角度,利用小发散角度实现了再现深度的拓展.与传统的多中心平面拓展技术相比,该方法具有系统结果简单,扩展效率高,对显示器件要求较低的优点.光学实验结果显示,当元素图像阵列中各像素点的发散角为1.79°时,集成成像三维再现深度是原来的6.4倍,比传统的多中心平面扩展技术实现的4倍再现深度提升了60％,为提高集成成像三维再现像的品质提供了一种有效的解决方法.     

基于磁悬浮式基因生物成像扫描仪电磁结构设计

针对常规基因生物芯片成像系统由于基因芯片位姿调整频繁而引起的调整机构机械磨损的关键问题,设计一种基于磁悬浮的基因生物芯片成像扫描仪。根据基因生物芯片成像扫描仪的工作原理及磁悬浮技术的结构特点,建立由电磁参数与成像分辨率组成的系统微分阵列,通过理论优化确定电磁结构参数,采用有限元分析法对系统进行电磁热结构耦合分析,优化分析结果并搭建实验测试装置。利用本装置对基因生物芯片成像扫描仪进行参数标定,验证扫描仪磁悬浮系统结构设计结果,并与进口PCR仪进行实验测试数据比对。结果表明,本文设计的磁悬浮式基因生物成像扫描仪电磁结构匝数为340 N时产生的有效电磁面积为180 mm~2,此时磁悬浮系统精度误差小于0.15 mm,与仿真数据基本吻合,与美国Bio-Rad数字PCR系统做T790M突变检测的数据对比实验所测得结果CV<5%。本文设计的基于磁悬浮的基因生物芯片成像扫描仪精度可以满足基因生物芯片成像检测的要求,为提升调整装置使用寿命方面提供核心技术保障,在提升临床肿瘤筛查、基因诊断技术中发挥重要的作用。     

盲复原高斯模糊图像

经典的图像恢复算法设点扩展函数(PSF)是已知的,然而在许多情况下PSF难以确定,不得不在只知道成像系统部分信息甚至没有任何信息的情况下估计真实图像和PSF,这一过程称为图像盲复原.对于高斯模糊图像,它的PSF是很难被检测出来的,因此高斯模糊图像的盲复原一直是个棘手的问题.利用高斯点扩展函数的特性,初始估计PSF并对加...