Speckle structured illumination endoscopy with enhanced resolution at wide field of view and depth of field

Structured illumination microscopy(SIM)is one of the most widely applied wide field super resolution imaging techniques with high temporal resolution and low phototoxicity.The spatial resolution of SIM is typically limited to two times of the diffraction limit and the depth of field is small.In this work,we propose and experimentally demonstrate a low cost,easy to implement,novel technique called speckle structured illumination endoscopy(SSIE)to enhance the resolution of a wide field endoscope with large depth of field.Here,speckle patterns are used to excite objects on the sample which is then followed by a blind-SIM algorithm for super resolution image reconstruction.Our approach is insensitive to the 3D morphology of the specimen,or the deformation of illuminations used.It greatly simplifies the experimental setup as there are no calibration protocols and no stringent control of illumination patterns nor focusing optics.We demonstrate that the SSIE can enhance the resolution 2–4.5 times that of a standard white light endoscopic(WLE)system.The SSIE presents a unique route to super resolution in endoscopic imaging at wide field of view and depth of field,which might be beneficial to the practice of clinical endoscopy.

Dynamic measurement of beam divergence angle of different fields of view of scanning lidar

The laser beam divergence angle is one of the important parameters to evaluate the quality of the laser beam.It can not only accurately indicate the nature of the beam divergence when the laser beam is transmitted over a long distance,but also objectively evaluate the performance of the laser system.At present,lidar has received a lot of attention as a core component of environment awareness technology.Micro-electromechanical system(MEMS)micromirror has become the first choice for three-dimensional imaging lidar because of its small size and fast scanning speed.However,due to the small size of the MEMS micromirror,the lidar scanning system has a small field of view(FOV).In order to achieve a wide range of scanning imaging,collimating optical system and wide-angle optical system are generally added to the system.However,due to the inherent properties of the optical lens,it is impossible to perfect the imaging,so the effects of collimating and expanding the beam will be different at different angles.This article aims to propose a measurement system that dynamically measures the divergence angles of MEMS scanning lidar beams in different fields of view to objectively evaluate the performances of scanning lidar systems.

A novel trigger algorithm for wide-field-of-view imaging atmospheric Cherenkov technique experiments

The high-altitude detection of astronomical radiation(HADAR)experiment is a new Cherenkov observation technique with a wide field of view(FoV),aimed at observing the prompt emissions ofγ-ray bursts(GRBs).The bottleneck for this type of experiment can be found in determining how to reject the high rate of nightsky background(NSB)noise from random stars.In this work,we propose a novel method for rejecting noise,which considers the spatial properties of GRBs and the temporal characteristics of Cherenkov radiation.In space coordinates,the map between the celestial sphere and the fired photomultiplier tubes(PMTs)on the telescope's camera can be expressed as f(δ(i,j))=δ'(i',j'),which means that a limited number of PMTs is selected from one direction.On the temporal scale,a 20-ns time window was selected based on the knowledge of Cherenkov radiation.This allowed integration of the NSB for a short time interval.Consequently,the angular resolution and effective area at 100 GeV in the HADAR experiment were obtained as 0.2°and 10^(4)m^(2),respectively.This method can be applied to all wide-FoV experiments.

Integral imaging-based tabletop light field 3D display with large viewing angle

Light field 3D display technology is considered a revolutionary technology to address the critical visual fatigue issues in the existing 3D displays.Tabletop light field 3D display provides a brand-new display form that satisfies multi-user shared viewing and collaborative works,and it is poised to become a potential alternative to the traditional wall and portable display forms.However,a large radial viewing angle and correct radial perspective and parallax are still out of reach for most current tabletop light field 3D displays due to the limited amount of spatial information.To address the viewing angle and perspective issues,a novel integral imaging-based tabletop light field 3D display with a simple flat-panel structure is proposed and developed by applying a compound lens array,two spliced 8K liquid crystal display panels,and a light shaping diffuser screen.The compound lens array is designed to be composed of multiple three-piece compound lens units by employing a reverse design scheme,which greatly extends the radial viewing angle in the case of a limited amount of spatial information and balances other important 3D display parameters.The proposed display has a radial viewing angle of 68.7°in a large display size of 43.5 inches,which is larger than the conventional tabletop light field 3D displays.The radial perspective and parallax are correct,and high-resolution 3D images can be reproduced in large radial viewing positions.We envision that this proposed display opens up possibility for redefining the display forms of consumer electronics.

Monte-Carlo simulation of pinhole collimator of a small field of view gamma camera for small animal imaging

Needs in scintimammography applications,especially for small animal cardiac imaging,lead to develop a small field of view,high spatial resolution gamma camera with a pinhole collimator.However the ideal pinhole collimator must keep a compromise between spatial resolution and sensitivity.In order to design a pinhole collimator with an optimized sensitivity and spatial resolution,the spatial resolution and the geometric sensitivity response as a function of the source to collimator distance has been obtained by means of Monte-Carlo simulation for a small field of view gamma camera with a pinhole collimator of various-hole diameters.The results show that the camera with pinhole of 1 mm,1.5 mm and 2 mm diameter has respectively spatial resolution of 1.5 mm,2.25 mm and 3 mm and geometric sensitivity of 0.016%,0.022%and 0.036%,while the source to collimator distance is 3 cm.We chose the pinhole collimator with hole diameter size of 1.2 mm for our the gamma camera designed based on the trade-off between sensitivity and resolution.

Flexible reduced field of view magnetic resonance imaging based on single-shot spatiotemporally encoded technique

In many ultrafast imaging applications, the reduced field-of-view（r FOV） technique is often used to enhance the spatial resolution and field inhomogeneity immunity of the images. The stationary-phase characteristic of the spatiotemporallyencoded（SPEN） method offers an inherent applicability to r FOV imaging. In this study, a flexible r FOV imaging method is presented and the superiority of the SPEN approach in r FOV imaging is demonstrated. The proposed method is validated with phantom and in vivo rat experiments, including cardiac imaging and contrast-enhanced perfusion imaging. For comparison, the echo planar imaging（EPI） experiments with orthogonal RF excitation are also performed. The results show that the signal-to-noise ratios of the images acquired by the proposed method can be higher than those obtained with the r FOV EPI. Moreover, the proposed method shows better performance in the cardiac imaging and perfusion imaging of rat kidney, and it can scan one or more regions of interest（ROIs） with high spatial resolution in a single shot. It might be a favorable solution to ultrafast imaging applications in cases with severe susceptibility heterogeneities, such as cardiac imaging and perfusion imaging. Furthermore, it might be promising in applications with separate ROIs, such as mammary and limb imaging.

Structured scene modeling using micro stereo vision system with large field of view

This paper presents a method for structured scene modeling using micro stereo vision system with large field of view. The proposed algorithm includes edge detection with Canny detector, line fitting with principle axis based approach, finding corresponding lines using feature based matching method, and 3D line depth computation.

Design of three-dimensional imaging lidar optical system for large field of view scanning

Three-dimensional(3D)lidar has been widely used in various fields.The MEMS scanning system is one of its most important components,while the limitation of scanning angle is the main obstacle to improve the demerit for its application in various fields.In this paper,a folded large field of view scanning optical system is proposed.The structure and parameters of the system are determined by theoretical derivation of ray tracing.The optical design software Zemax is used to design the system.After optimization,the final structure performs well in collimation and beam expansion.The results show that the scan angle can be expanded from±5°to±26.5°,and finally the parallel light scanning is realized.The spot diagram at a distance of 100 mm from the exit surface shows that the maximum radius of the spot is 0.506 mm with a uniformly distributed spot.The maximum radius of the spot at 100 m is 19 cm,and the diffusion angle is less than 2 mrad.The energy concentration in the spot range is greater than 90%with a high system energy concentration,and the parallelism is good.This design overcomes the shortcoming of the small mechanical scanning angle of the MEMS lidar,and has good performance in collimation and beam expansion.It provides a design method for large-scale application of MEMS lidar.

Impact of random and scattered coincidences from outside of field of view on positron emission tomography/computed tomography imaging with different reconstruction protocols

Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction protocols.In this study,we investigated the effects of scattered and random coincidences from outside the field of view(FOV)on PET image quality for different reconstruction protocols.Imaging was performed on the Discovery 690 PET/CT scanner,using experimental configurations including the NEMA phantom(a body phantom,with six spheres of different sizes)with a signal background ratio of 4:1.The NEMA phantom(phantom I)was scanned separately in a one-bed position.To simulate the effect of random and scatter coincidences from outside the FOV,six cylindrical phantoms with various diameters were added to the NEMA phantom(phantom II).The 18 emission datasets with mean intervals of 15 min were acquired(3 min/scan).The emission data were reconstructed using different techniques.The image quality parameters were evaluated by both phantoms.Variations in the signal-to-noise ratio(SNR)in a 28-mm(10-mm)sphere of phantom II were 37.9%(86.5%)for ordered-subset expectation maximization(OSEM-only),36.8%(81.5%)for point spread function(PSF),32.7%(80.7%)for time of flight(TOF),and 31.5%(77.8%)for OSEM+PSF+TOF,respectively,indicating that OSEM+PSF+TOF reconstruction had the lowest noise levels and lowest coefficient of variation(COV)values.Random and scatter coincidences from outside the FOV induced lower SNR,lower contrast,and higher COV values,indicating image deterioration and significantly impacting smaller sphere sizes.Amongst reconstruction protocols,OSEM+PSF+TOF and OSEM+PSF showed higher contrast values for sphere sizes of 22,28,and 37 mm and higher contrast recovery coefficient values for smaller sphere sizes of 10 and 13 mm.

Calibration of Camera with Large Field-of-View Based on Flexible Planar Target

For high precision calibration of camera with large field-of-view,massive calibration points will be needed if traditional methods are selected,which makes the calibration complex and time-consuming.In order to solve this problem,a calibration method based on flexible planar target is proposed.In this method,distortion factor is firstly acquired by the invariance of cross ratio,and existing feature points are adjusted with the distortion factor.Then,a large number of points that will be used for the calibration are constructed with the adjusted feature points.Simultaneously,Tsai method is modified so as to reduce the complexity of calibration,which makes the process linear.The simulation and real experiments show that the method proposed in this paper is simple,linear,accurate and robust,and the precision of this method is close to that of Tsai method using abundant points.The method can satisfy the requirement of high precision calibration for camera with large field-of-view.

r-fov IVIM与r-fov DWI模型参数早期预测乳腺癌新辅助化疗疗效价值的比较

目的 比较磁共振小视野体素不相干运动扩散加权成像(reduced field of view,intravoxel incoherent motion,r-fov IVIM)及小视野常规扩散加权成像(reduced field of view,diffusion weighted imaging,r-fov DWI)模型参数预测乳腺侵润性导管癌新辅助化疗疗效的价值。方法 前瞻性选取28例单侧乳腺浸润性导管癌患者,收集化疗前、化疗2周期后乳腺r-fov IVIM模型参数真性扩散系数(Dt),假性扩散系数(Dp),灌注分数(f);r-fov DWI参数表观扩散系数(ADC)。根据术后病理结果分为组织学非显著反应组13人,组织学显著反应组15人;采用SPSS 25.0对数据进行处理,比较NAC前和化疗2个周期后两组间的参数值差异。绘制受试者工作特征曲线(receiver operating characteristic,ROO曲线分析以上参数对新辅助化疗疗效的预测价值。结果NAC2周期后ADC值,NAC2周期后与NAC前参数差值ΔADC、ΔDt值,三者的曲线下面积(area under curve,AUC)最大(0.951 VS 0.914、0.914),预测MHR组的效能高;NAC2周期后的Dt值,预测MHR组的效能较好(AUC=0.827)。结论 NAC2周期后,r-fov DWI模型参数ADC值和r-fov IVIM模型参数Dt值越高,且较NAC前升高程度越大,新辅助化疗结束后越容易获得较好的疗效;其中,以NAC2周期后,r-fovDWI模型参数ADC值的预测效能最高,应作为乳腺癌浸润性导管癌临床治疗过程中,新辅助化疗反应评估的主要参考参数。

Study of a millimeter-wave squint indirect holographic algorithm suitable for imaging with large field-of-view

In this paper a millimeter-wave （MMW） squint indirect holographic method is presented, which is suitable for imaging with a large field-of-view. The proposed system employs the squint operation mode to remove the background and twin- image interferences, which achieves a similar effect to off-axis holography but leaves out the large-aperture quasi-optical component. The translational scanning manner enables a large field of view and ensures the image uniformity, which is difficult to realize in off-axis holography. In addition, a corresponding imaging algorithm for the presented scheme is developed to reconstruct the image from the recorded hologram. Some imaging results on typical objects, obtained with electromagnetic simulation, demonstrate good performance of the imaging scheme and validate the effectiveness of the image reconstruction algorithm.

小FOV用于256层CT前瞻性心电门控冠状动脉成像

目的探讨小FOV用于256层CT前瞻性心电门控冠状动脉成像(CTCA)的可行性。方法收集拟接受CTCA的疑似冠状动脉粥样硬化性心脏病患者120例,随机分为小FOV组(FOV<200mm)和大FOV组(FOV≥200mm),各60例,行前瞻性心电门控CTCA,比较组间图像质量、容积CT剂量指数(CTDIvol)、扫描长度、剂量长度乘积(DLP)及有效辐射剂量(ED)的差异。结果小FOV组和大FOV组FOV分别为(173.55±11.34)mm和(231.40±12.44)mm。小FOV组与大FOV组图像质量评分差异无统计学意义[(3.85±0.52)vs(3.77±0.46)分,P>0.05];小FOV组CTDIvol[(19.28±0.24)mGy]、扫描长度[(121.95±7.72)mm]、DLP[(234.97±13.30)mGy/cm]和ED[(3.28±0.19)mSv]均显著低于大FOV组[CTDIvol:(20.52±0.57)mGy、扫描长度:(133.32±8.90)mm、DLP:(273.87±24.45)mGy/cm、ED:(3.84±0.35)mSv,P均<0.001]。结论 256层前瞻性心电门控CTCA中,采用小FOV可在保证图像质量的同时明显降低辐射剂量。

Estimation of IFOV of Rosette Scan System

The methods of estimating the minimum allowed value of IFOV (instantaneous field of view) of the detector in a rosette scan system are investigated. The common method for the estimation of IFOV is described. A new method which uses the maximum distance between two neighboring petals as the estimated value of IFOV is developed and a comparison between the common method and the new method is given. It is concluded that the minimum allowed value of IFOV of rosette scanning is over estimated by the common method while this value can be calculated accurately with the new method.

非对等FOV作用下的高分辨率FTIRS仪器线型函数研究

视场角(FOV)是仅次于最大光程差、决定高分辨率傅里叶红外光谱仪(FTIRS)仪器线型函数(ILS)的重要因素。由于光学设计和装调原因,理论为圆形FOV的扩散光束,到达探测器端时,其水平和垂直方向上的FOV值往往不再严格对等。对此,提出了以椭圆形面光源取代传统文献中的圆形面光源来反映这种非对等性,并结合最大光程差参数,给出了非对等FOV作用下的高分辨率FTIRS仪器线型函数的数学和图形表述。通过比较高分辨率FTIRS实测CO标气获得的光谱,与非对等FOV、对等FOV作用下的理论光谱,发现非对等FOV作用下的理论谱与实测谱的差谱RMS值较对等FOV获得的差谱RMS值更小,在最大吸收峰附近的差谱变化更为平缓。表明了这种非对等FOV作用下的ILS函数,较对等FOV作用下的ILS函数能更精确的反映高分辨率FTIRS对谱线的真实响应。

Adaptive weighting impact angle optimal guidance law considering seeker's FOV angle constraints

In this paper, a new adaptive optimal guidance law with impact angle and seeker’s field-of-view(FOV) angle constraints is proposed. To this end, the generalized optimal guidance law is derived first. A changeable impact angle weighting(IAW) coefficient is introduced and used to modify the guidance law to make it adaptive for all guidance constraints. After integrating the closed-form solution of the guidance command with linearized engagement kinematics, the analytic predictive models of impact angle and FOV angle are built, and the available range of IAW corresponding to constraints is certain. Next, a calculation scheme is presented to acquire the real-time value of IAW during the entire guidance process. When applying the proposed guidance law, the IAW will keep small to avoid a trajectory climbing up to limit FOV angle at an initial time but will increase with the closing target to improve impact position and angle accuracy, thereby ensuring that the guidance law can juggle orders of guidance accuracy and constraints control.

SFOV对成人胸部CT水当量直径的体型特异性剂量估算的影响研究

目的探讨扫描野(Scanning Field of View,SFOV)对成人胸部CT水当量直径的体型特异性剂量估算(Water Equivalent Diameter of Size-Specific Dose Estimates,SSDE_(WED))的影响。方法回顾性分析2020年7至8月我院行胸部CT扫描的162例成人受检者,选取原始序列横断位中间层面图像,勾画圆形感兴趣区(Region of Interest,ROI),测量ROI的CT_(ROI)值、面积A_(ROI),记录受检者的性别、年龄、容积剂量指数(Volume CT Dose Index,CTDI_(vol))、剂量长度乘积(Dose Length Product,DLP)和SFOV的数值,计算每例受检者中间层面的水等效直径(Water Equivalent Diameter,WED)、转换因子(f_(size·WED))和SSDE_(WED)。利用多元回归分析性别、年龄、CT_(ROI)、A_(ROI)、CTDI_(vol)、DLP和SFOV与SSDE_(WED)的相关性。结果性别、年龄、A_(ROI)、CTDI_(vol)、DLP和SFOV与SSDE_(WED)有显著差异(P<0.05),CT_(ROI)与SSDE_(WED)无显著差异(P>0.05),多元回归分析SSDE_(WED)与SFOV呈0.06倍正线性相关。结论SFOV对成人胸部CT的SSDE_(WED)影响较大,且呈0.06倍正线性相关,在临床扫描中精准调节SFOV可以降低成人受检者胸部CT辐射剂量。

FOV线生成的一种新方法

在多摄像机跟踪中,主要的难点是如何在多个摄像机之间对相同的目标建立正确的对应关系。摄像机视野边界(FOV)线是近年来出现的一种新的有效的解决多摄像机跟踪中目标交接问题的工具。因此,精确生成视野边界线成了解决问题的关键所在。根据投影不变量FOV线生成法,在生成视野边界线时不依赖于场景中目标的运动,并且不需要摄像机参数的信息。应用PETS2001数据库里的两组不同序列进行尝试,实验结果表明,对于视野边界线恢复,其鲁棒性与可靠性都较好。

MRI超清r-FOV DWI诊断胃部病变的临床价值

目的探讨MRI超清小视野扩散加权成像(r-FOV DWI)诊断及鉴别诊断胃部病变的临床价值。方法搜集34例经胃镜及病理检查证实的胃部疾病患者,利用1.5T MRI扫描仪行常规MRI平扫、r-FOV DWI与常规视野(c-FOV DWI)扫描(b=1000 s/mm2),对病变区与正常胃壁的表观扩散系数(ADC)值分别采用r-FOV DWI与c-FOV DWI图像测量。同时由2位影像诊断医师采用盲法利用4分法,分别对r-FOV DWI及c-FOV DWI图像质量进行主观评分和比较。结果观察者主观评分r-FOV DWI为(3.47±0.50)分,明显高于c-FOV DWI的主观性评分(2.63±0.79)分(P<0.05)。2位影像诊断医师对r-FOV DWI与c-FOV DWI图像主观评分的一致性良好(Kappa值=0.706);r-FOV DWI与c-FOV DWI在正常胃壁、胃腺癌、胃炎、胃淋巴瘤及胃异位胰腺上的ADC值差异无统计学意义(P>0.05)。结论 MRI的r-FOV DWI对诊断及鉴别胃部病变有较好的效果,将两者结合使用有效提高诊断正确率,有利于临床诊断及治疗。

基于LabVIEW的火车轮面裂纹深度在线监测技术

针对高速高温运行时火车车轮踏面裂纹检测困难且精度差的问题,采用虚拟仪器技术开发了一种基于电磁超声检测的深度在线检测方案。为了解决电磁超声系统的EMTS限制,设计了一款新型磁场发生器,满足测量磁场的发射要求。通过引入比例积分控制算法提高电流控制精度,利用深度学习网络降低大规模信号噪声分析的操作成本,从而有效提升测量精度和信号的分析效率。由实验与测试结果可知,文中所提方法的电流控制精度在0.01%以内,系统分析精度随着测量距离和数据量的增大而有所提高,为工程应用提供了参考。