The Flipping-Free Full-Parallax Tabletop Integral Imaging with Enhanced Viewing Angle Based on Space-Multiplexed Voxel Screen and Compound Lens Array

Tabletop integral imaging display with a more realistic and immersive experience has always been a hot spot in three-dimensional imaging technology,widely used in biomedical imaging and visualization to enhance medical diagnosis.However,the traditional structural characteristics of integral imaging display inevitably introduce the flipping effect outside the effective viewing angle.Here,a full-parallax tabletop integral imaging display without the flipping effect based on space-multiplexed voxel screen and compound lens array is demonstrated,and two holographic functional screens with different parameters are optically designed and fabricated.To eliminate the flipping effect in the reconstruction process,the space-multiplexed voxel screen consisting of a projector array and the holographic functional screen is presented to constrain light beams passing through the corresponding lens.To greatly promote imaging quality within the viewing area,the aspherical structure of the compound lens is optimized to balance the aberrations.It cooperates with the holographic functional screen to modulate the light field spatial distribution.Compared with the simulation results,the distortion rate of the imaging display is reduced to less than 9%from more than 30%.In the experiment,the floating high-quality reconstructed three-dimensional image without the flipping effect can be observed with the correct 3D perception at 96°×96°viewing angle,where 44,100 viewpoints are employed.

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.

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.

Preventing condensation of objective lens in noncontact wide-angle viewing systems during vitrectomy

AIM： To assess the optimal conditions for preventing condensation of objective lens during vitrectomy with noncontact wide-angle viewing systems（WAVSs）. METHODS： We explored the effectiveness of the coating with ophthalmic viscoelastic device（OVDs） on the corneal surface and the soaking the objective lens in warm-saline for preventing condensation of objective lens. First, to find the optimal soaking time to keep the objective lens warm, we measured the temperature of objective lens every minute after soaking in warm saline. Second, to find optimal distance between cornea and objective lens, which provide as wide a view as possible and less condensation at the same time, we measured the condensation time with different distances. With the obtained optimal soaking time and distance, we explored the effect of coating cornea with OVDs and soaking objective lens in warm saline on condensation time.RESULTS： One and 5 min of soaking in warm saline was most effective for keeping the lens warm enough（45.1℃±2.1℃ for 1 min and 46.4℃±1.0℃ for 5 min, P=0.109）. The mean condensation times for the control group at 1, 3, and 5 mm from corneal surface to objective lens were 1±0.4, 4±1.4, 190±26.1 s, respectively, thus 5 mm was most optimal distance for vitrectomy with WAVSs. For the OVD coating group, the mean condensation times were 1.5±0.3, 13±1.4, and 200±23.9 s at 1, 3, and 5 mm distance and borderline significant compared with control group（P=0.068, 0.051, and 0.063, respectively）. With the 1-minute warm saline soaking group, the mean condensation time were extended to 188±34.4, 416±65.7, and 600±121.3 s at 1, 3, and 5 mm distance and statistically significant compared with control（P=0.043, 0.041 and 0.043, respectively）.CONCLUSION： OVD coating on corneal surface shows no difference on condensation time with control group. However, soaking the objective lens in warm saline revealed statistically significant extension of condensation time compared to control group. Therefore, keeping the objective lens warm with soaking in warm saline is a simple but effective to prevent condensation of objective lens during vitrectomy. The thermodynamics between objective lens and cornea during vitrectomy warrants further investigation.

Comparison of scleral buckling using wide-angle viewing systems and indirect ophthalmoscope for rhegmatogenous retinal detachment

AIM：To compare the effects of scleral buckling using wide-angle viewing systems（WAVS） with that using indirect ophthalmoscope for the treatment of rhegmatogenous retinal detachment.METHODS：The study was a retrospective analyses of the medical records of 94 eyes（94 patients） with rhegmatogenous retinal detachment.Among them,47 eyes underwent scleral buckling using WAVS with endoiiluminator（Group W）,and 47 eyes underwent scleral buckling using indirect ophthalmoscope（Group I）.Surgical durations,primary success rate,best-corrected visual acuities（BCVA）,delayed subretinal fluid absorptions and surgical complications were compared between the two groups.RESULTS：At baseline,there were no statistical differences between the two groups in patient＇s age（P=0.997）,gender（P=0.853）,symptom duration（P=0.216）,BCVA（P=0.389）,refractive error（P=0.167）,intraocular pressure（P=0.595）,the number of retinal breaks（P=0.832）,the extent of retinal detachment（P =0.246）,subretinal demarcation line（P=0.801）,and macular detachment（P=0.811）.The follow-up period was 12 mo.The surgical durations in Group W（with or without encircling buckling） were significant shorter than those in Group I（P〈0.001 respectively）.The primary success rate was94.27%in Group W,which was similar to that in Group I（92.38%,P=0.931）.The BCVA in Group W was better than that in Group I（P〈0.001） at 1-month follow-up visit.However,there were no significant differences between the two groups at 3-month（P=0.221）,6-month（P =0.674）,and 12-month（P=0.363） follow-up visits respectively.Delayed subretinal fluid absorptions were more common in Group I than in Group W at 1-month（P=0.045） follow-up visit,but there were no significant differences between the two groups at 3-month（P=0.111）,6-month（P =1.000） and 12-month follow-up visits respectively.CONCLUSION：Scleral buckling using WAVS can be an alternative choose for rhegmatogenous retinal detachment

一种全新的LCD宽视角技术

在边缘场开关模式向列液晶盒内,不论是在电极之间的液晶分子还是电极之上的液晶分子都可以在边缘场的驱动下转动,所以它具有比共面转换模式更好的透光率和宽视角特性。本文对这两种模式的结构和原理进行了比较,并介绍了针对其自身存在的不足所进行的各种改进方法的原理、结构和改进效果,对各种方法的优缺点做出了评述。

The correlation of multi-angle thermal infrared data and the choice of optimal view angles

Based on the matrix formula of thermal infrared radiant system, the components temperature can be retrieved by the inversive matrix. Around the stability problem of retrieved result, the research work we did was focused on (i) the correlation of (wk,j) which is the key to affect the retrieval accuracy, (ii) a general method which can help us find the number of retriev-able parameters and evaluate the retrieval error before its performance, (iii) the choice of 搊pti-mal viewing angle group?based on the formula of absolute error propagation. The row winter wheat field was chosen as an example. The results can provide a theoretical basis for multi-angle thermal infrared remote sensing and components temperature retrieval.

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.

基于角度传感器的弓网相对坐标检测技术研究

在电气化公路弓网相对坐标的检测中,基于机器视觉的非接触式检测技术的检测精度受图像采集环境的影响较大,基于光电传感器的接触式检测技术的检测精度受传感器安装密度限制。提出了一种基于角度传感器的接触式相对坐标检测技术,用于电气化公路的弓网相对坐标检测。首先,基于双接触线的电气化公路接触网,搭建弓网相对坐标检测实验台,建立弓网相对坐标与角度信息关联函数;然后,研究系统刚度、角度传感器线性度对实验台检测误差的影响规律,建立多项式修正函数对关联函数进行修正;最后,基于修正的弓网相对坐标关联函数,进行弓网相对坐标检测实验,得到实验台检测的绝对误差为±1 mm,相对误差为±0.5%,具备较高的检测精度。

有限视场下的攻击时间和角度多约束制导律

针对精确打击任务存在导引头视场受限这一过程约束的制导问题,提出了一种考虑视场限制以及攻击角度和时间多种约束的制导律.首先,在以比例导引项实现精确命中的基础上,利用最优控制理论,采用弹目距离加权控制能耗形式的指标函数,设计了攻击角度控制项,并推导了相应的剩余飞行时间解析预测表达式.其次,基于最优误差动力学方法,设计了攻击时间相关的控制项,保证了攻击时间误差的有限时间收敛.同时,针对导引头视场有限的问题,分析了各控制项对前置角收敛性的影响,利用特定的限制函数确保前置角在整个制导过程中始终处于有效视场内,并给出了前置角的有界性及收敛性证明.数学仿真结果验证了所提出制导律对多约束制导问题的有效性.

膝关节参数在膝前疼痛中的意义

背景:膝关节参数如合适角异常对于膝前疼痛有统计学意义已在CT测量下证实,但是没有在临床手术实践中证实。目的:通过对膝前疼痛患者髌骨X射线轴位片上的合适角、髌股指数、外侧髌股角、倾斜角等参数的测量,分析这些参数对膝前疼痛的诊断价值。方法:纳入不同程度髌股关节软骨损伤的膝前痛患者50例患者的50个膝关节,测量髌骨X射线轴位片上合适角、髌股指数、外侧髌股角、倾斜角参数,同时与50例无膝前痛仅存在半月板损伤的50个膝关节进行比较。结果与结论:髌骨X射线轴位片的合适角及髌股指数、倾斜角对于膝前疼痛有显著性差异,外侧髌股角无显著性差异。髌骨X射线轴位片的合适角、髌股指数对由髌股关节紊乱导致的膝前疼痛患者有重要的诊断治疗价值,是对髌股关节紊乱具有临床意义的有效参数。

宽波段大视角液晶偏振转换器研究进展

偏振转换器能够通过对入射光偏振态的动态调控间接实现几何相位型多功能光学器件光学响应特性的动态可调。基于液晶的偏振转换器具有调控效率高、调控面积大、紧凑化程度高等诸多优势,是目前应用较为广泛的偏振转换器。本文围绕偏振转换效率、工作波段、视场角3个核心参量,系统介绍了液晶偏振转换器最新的研究进展,分别给出了典型液晶偏振转换器和大视角宽波段液晶偏振转换器的详细结构和性能表现,同时介绍了液晶偏振转换器工作波段和视角的拓展方法。该项工作能够为液晶偏振转换器结构设计与应用提供必要的参考,同时为基于几何相位或新型相位调控模式的研究提供一些思路。

基于ADAMS/View车轮前束和外倾对侧滑的影响分析

车轮外倾角和前束的检测非常重要,一旦车轮外倾角和前束匹配不当,就会造成轮胎磨损加剧,严重影响汽车的动力性、经济性,甚至安全性。该文使用ADAMS软件中的ADAMS/View模块,建立双横臂式前独立悬架模型,改变模型的前束和外倾角,在不同的前束和外倾角条件下对模型进行仿真,测量车轮底部的侧向滑移量,以分析二者对车轮侧滑的影响。

红外光谱辐射计镜头视场角测量研究

红外光谱辐射计作为经典的航空发动机红外辐射强度测试仪器,具有光谱分辨率高、测量精度高、响应快、光谱范围广等优点。在使用过程中,红外光谱辐射计需要根据被测目标尺寸及测量距离选择合适的镜头,利用测量的光谱辐射亮度乘以镜头视场的面积,才能得到发动机红外辐射强度。由于加工及装配误差,红外光谱辐射计配套镜头的视场角会偏离其出厂默认值,导致测试偏差。设计了一种红外光谱辐射计镜头视场角测量方法,制作了测量装置,并测量了VSR-3型红外光谱辐射计的标准镜头的视场角。测量结果表明:镜头有效视场角与出厂默认角度存在4%的偏差。通过修正该偏差,能够提高航空发动机红外辐射强度测量精度。

面向移动机器人大视角运动的图神经网络视觉SLAM算法

针对移动机器人在大视角运动下光照变化剧烈或遭遇纹理稀疏场景易出现特征点提取困难,极端角度下特征难以匹配导致对极几何计算误差较大问题,提出一种融合改进图神经网络的视觉SLAM算法。基于先验位置估计的特征提取网络,通过先验位置估计实现图像特征点快速均匀检测与描述,构建真实准确的特征点信息。基于图注意力机制的特征匹配网络,通过消息传递图神经网络聚合特征点信息,使用自我与联合注意力机制对前后图像帧分权重特征匹配。将特征提取与匹配图神经网络与ORB-SLAM2系统后端非线性优化、闭环修正、局部建图模块融合,提出一个完整的单目视觉GNN-SLAM系统。实验结果表明:该算法在KITTI数据集上与ORB-SLAM2算法相比,绝对轨迹误差降低37.59%,相对位姿误差降低19.67%。

从多维视野看高校党委中心组学习的意义、内容和方法

从哲学的、领导学的、心理学的多维视野分析高校党委中心组学习的科学化问题 ,所得出的结论是 ,高校党委中心组学习在学习成员的认识发展中具有极其重要的意义。高校党委中心组学习内容的安排必须突出重点 ,开拓眼界 ,学以致用 ;学习组织必须重视学习成员动机、注意、理解。

基于ADAMS/View的偏牵引梳齿式采棉机侧向稳定性分析

【目的】研究偏牵引梳齿式采棉机的侧向稳定性,验证工作时是否会发生侧向滑移以及工作的稳定性。【方法】应用Solidworks对梳齿式采棉机进行三维实体建模,并导入ADAMS/View软件。利用ADAMS专用模块构建轮胎、路面约束,并施加相关驱动、约束和力,建立完整的动力学模型,通过运动仿真观察采棉机作业时位移变化曲线,判断是否能稳定工作。【结果】梳齿式采棉机工作状态下,采摘台和拖拉机没有发生侧滑,均沿着直线前行。【结论】梳齿式采棉机在拖拉机牵引下作业,偏牵引角小于摩擦角,整机满足偏牵引稳定性条件。

基于前光模组的反射式液晶显示视角

反射式液晶显示具有功耗低、绿色环保的优点。但由于没有增亮膜等光学膜系对视角进行调控,常见的网点形貌下视角曲线存在跳变、不均匀等问题。为了改善反射式液晶显示的视角问题,本文建立了反射式液晶模组仿真模型进行探究。首先,分析了前光模组存在的视角问题。接着,以圆锥形和圆台形网点为例分析了网点形貌对视角的影响,并提出棱柱形网点以改善视角。仿真结果表明,棱柱形网点可以有效解决垂直于入射光方向±35°视角的曲线跳变及不均匀问题,且将视角中心亮度相比于圆锥形网点提升了52.3%。本研究对反射式液晶显示设备的视角设计具有重要参考意义。

基于绘画观赏视角的展陈光环境研究

为研究基于绘画观赏视角的展陈光环境参数,本文从参观者视觉体验和需求出发,在主观感受层面讨论绘画视觉外观的影响规律并提出分析工具。通过对山水、人物、花鸟类国画的研究发现,3000~5600 K色温展陈光环境更受偏爱,观赏效果与色温高低显著相关;照度50~300 lx时,国画观赏效果与照度显著相关,最佳色温照度组合为5600 K-300 lx。3000 K-50 lx光环境下较低反射率的背景和5600 K-50 lx光环境下较高反射率的背景都能提高观赏效果;3000 K-50 lx光环境下,国画展品的“可见性”和“质感”与展陈背景颜色深浅度相关;5600 K-50 lx光环境下,仅国画展品的“质感”与展陈背景颜色深度相关较强。