DiriNet:An Estimation Network for Spectral Response Function and Point Spread Function

Hyper-and multi-spectral image fusion is an important technology to produce hyper-spectral and hyper-resolution images,which always depends on the spectral response function andthe point spread function.However,few works have been payed on the estimation of the two degra-dation functions.To learn the two functions from image pairs to be fused,we propose a Dirichletnetwork,where both functions are properly constrained.Specifically,the spatial response function isconstrained with positivity,while the Dirichlet distribution along with a total variation is imposedon the point spread function.To the best of our knowledge,the neural network and the Dirichlet regularization are exclusively investigated,for the first time,to estimate the degradation functions.Both image degradation and fusion experiments demonstrate the effectiveness and superiority of theproposed Dirichlet network.

PET image reconstruction with a system matrix containing point spread function derived from single photon incidence response

A point spread function（PSF） for the blurring component in positron emission tomography（PET） is studied. The PSF matrix is derived from the single photon incidence response function. A statistical iterative reconstruction（IR） method based on the system matrix containing the PSF is developed. More specifically, the gamma photon incidence upon a crystal array is simulated by Monte Carlo（MC） simulation, and then the single photon incidence response functions are calculated. Subsequently, the single photon incidence response functions are used to compute the coincidence blurring factor according to the physical process of PET coincidence detection. Through weighting the ordinary system matrix response by the coincidence blurring factors, the IR system matrix containing the PSF is finally established. By using this system matrix, the image is reconstructed by an ordered subset expectation maximization（OSEM） algorithm. The experimental results show that the proposed system matrix can substantially improve the image radial resolution, contrast,and noise property. Furthermore, the simulated single gamma-ray incidence response function depends only on the crystal configuration, so the method could be extended to any PET scanner with the same detector crystal configuration.

Point spread functions for a small gamma camera with pinhole collimator

A set of point spread functions (PSF) has been obtained by means of Monte-Carlo simulation for asmall gamma camera with a pinhole collimator of various hole diameters. The FOV (field of view) of the camera isexpended from 45 mm to 70 mm in diameter. The position dependence of the variances of PSF is presented, and theacceptance for the 140 kev gamma rays is explored. A phantom of 70 mm in diameter was experimentally imaged inthe camera with effective FOV of only 45 mm in diameter.

Bistatic Synthetic Aperture Radar Point Spread Function Characteristic Analysis

Based on the point spread function （PSF） theory, the side-lobe extension direction of the impulse response in bistatic synthetic aperture radar （BSAR） is analyzed in detail; in addition, the corresponding autofocus in BSAR should be considered along iso-range direction, not the traditional azimuth resolution （AR） direction. The conclusion is verified by the computer simulation.

A Knife-edge Input Point Spread Function Estimation Method for Document Images

In this paper the progress of document image Point Spread Function （PSF） estimation will be presented. At the beginning of the paper, an overview of PSF estimation methods will be introduced and the reason why knife-edge input PSF estimation method is chosen will be explained. Then in the next section, the knife-edge input PSF estimation method will be detailed. After that, a simulation experiment is performed in order to verify the implemented PSF estimation method. Based on the simulation experiment, in next section we propose a procedure that makes automatic PSF estimation possible. A real document image is firstly taken as an example to illustrate the procedure and then be restored with the estimated PSF and Lucy-Richardson deconvolution method, and its OCR accuracy before and after deconvolution will be compared. Finally, we conclude the paper with the outlook for the future work.

基于PSF的太赫兹图像分辨率增强算法

近年来,太赫兹成像技术在多个领域具有广阔的应用。一套完整的太赫兹成像系统的数学模型是非常有必要的。基于点扩散函数的太赫兹图像增强模型是很好的选择。该方法将目标函数与点扩散函数进行褶积,实现了太赫兹图像的模拟传输。然后根据光学成像的过程,计算成像系统的点扩散函数。最后,基于点扩散函数对图像进行反褶积增强。该模型用于探测图像增强的结果表明,该方法有效地提高了图像的分辨率。恢复的映像包含更多细节。

Analyzing the Effect of the Intra-Pixel Position of Small PSFs for Optimizing the PL of Optical Subpixel Localization

Subpixel localization techniques for estimating the positions of point-like images captured by pixelated image sensors have been widely used in diverse optical measurement fields.With unavoidable imaging noise,there is a precision limit(PL)when estimating the target positions on image sensors,which depends on the detected photon count,noise,point spread function(PSF)radius,and PSF’s intra-pixel position.Previous studies have clearly reported the effects of the first three parameters on the PL but have neglected the intra-pixel position information.Here,we develop a localization PL analysis framework for revealing the effect of the intra-pixel position of small PSFs.To accurately estimate the PL in practical applications,we provide effective PSF(e PSF)modeling approaches and apply the Cramér–Rao lower bound.Based on the characteristics of small PSFs,we first derive simplified equations for finding the best PL and the best intra-pixel region for an arbitrary small PSF;we then verify these equations on real PSFs.Next,we use the typical Gaussian PSF to perform a further analysis and find that the final optimum of the PL is achieved at the pixel boundaries when the Gaussian radius is as small as possible,indicating that the optimum is ultimately limited by light diffraction.Finally,we apply the maximum likelihood method.Its combination with e PSF modeling allows us to successfully reach the PL in experiments,making the above theoretical analysis effective.This work provides a new perspective on combining image sensor position control with PSF engineering to make full use of information theory,thereby paving the way for thoroughly understanding and achieving the final optimum of the PL in optical localization.

飞行时间和点扩散函数对18F-FDGPET/CT肺癌纵隔淋巴结转移的增益价值

目的探讨飞行时间(TOF)和点扩散函数(PSF)重建对18F-FDGPET/CT显像肺癌纵隔淋巴结转移的增益价值。资料与方法回顾性分析2020年3月9日—2021年7月23日在佛山市第一人民医院行PET/CT检查的肺癌纵隔淋巴结转移患者68例。分别采用有序子集最大期望值迭代法(OSEM)、OSEM+TOF、OSEM+PSF、OSEM+TOF+PSF重建图像,比较不同重建算法对肺癌纵隔淋巴结转移病灶的分辨能力,以及病灶信噪比(SNR)和标准化摄取值(SUV)的差异。结果使用OSEM+TOF+PSF重建可获得病灶SUVmax、SUVmean和SNR的最高值,与常规OSEM比较分别增加了21.99%、22.86%和60.14%(t=28.321、19.11、11.059,P均<0.01);其差异百分比在直径≤22 mm的较小病灶中明显大于直径>22 mm的较大病灶(24.1%比21.1%、25.3%比19.3%、70.6%比63.3%;Z=-3.658、-4.313、-2.154,P均<0.05),在SNR≤15.31的低对比度病灶中明显大于SNR>15.31的高对比度病灶(23.6%比21.4%、25.3%比21.1%、85.7%比46.0%;Z=-3.519、-2.336、-5.106,P均<0.05);在不同重建算法的病灶可检测性评价结果中,OSEM+TOF+PSF图像对纵隔淋巴结转移病灶的显示最清晰,其中87.4%的病灶为明确存在,显著高于OSEM图像的73.1%(χ^(2)=11.704,P=0.001),但OSEM+PSF图像中病灶明确存在的比例与OSEM比较并未显著增加(73.1%比75.8%;χ^(2)=0.361,P=0.548)。结论TOF和PSF结合能显著提高肺癌纵隔淋巴结转移病灶的探测能力,以及病灶SNR和SUV,尤其在小病灶和低对比度病灶中更为显著。

基于边缘约束与范数比值的图像盲复原

针对现有的研究方法对运动所引起的模糊图像进行复原时效果欠佳的问题,提出一种基于边缘约束与范数比值的图像盲复原算法.该算法首先对退化图像的边缘进行约束,得到图像的强边缘结构,提高了点扩散函数估计的准确率;然后对要估计的清晰图像构造范数比值的稀疏惩罚约束项,并将得到的强边缘信息与构造的范数比值惩罚约束项进行结合用于指引点扩散函数的复原;在对点扩散函数进行复原时,由粗到细多尺度交替迭代估计点扩散函数,使得迭代出的最大尺度更加精确;最后对图像进行非盲解卷积求解,使其复原.该算法将退化图像的边缘信息与构造的范数比值惩罚约束项进行结合指导点扩散函数的复原,可以抑制图像在复原过程中产生的大量伪迹.实验结果表明,该算法对恢复图像边缘细节具有很好的效果,可以得到优质的复原图像.

类THAAD导引头气动光学效应计算研究

针对类美国末段高空域防御(Terminal High Altitude Area Defense,THAAD)系统的红外导引头外形,开展了气动光学效应计算分析,并将其用于飞行器设计。利用国家数值风洞工程高速流场计算软件NNW-HyFLOW,考虑热化学非平衡效应和材料传热耦合效应,对导引头典型状态的流场进行了模拟,获得了流场的密度、温度、压力等参数和窗口的温度场参数。基于流场参数,利用HyFLOW气动光学传输效应计算功能,开展了红外光学传输成像计算;利用HyFLOW气动光学辐射效应计算模块,开展了流场和光学窗口的热辐射计算。计算结果表明,类THAAD导引头在30 km以上飞行时,流场和光学窗口基本不会影响目标信号的光学传输成像,但流场和窗口的热辐射效应会对导引头识别目标造成影响。不过随着飞行高度的升高,这种影响会减小。

CBERS-1 PSF估计与图像复原

分析了遥感图像获取过程中导致图像退化模糊的原因。讨论了一种借助图像中的特定线状目标信息 (如桥梁、堤坝等 ) ,采用经验拟合的方式提取图像获取、传输过程中的点扩散函数 ,并利用该点扩散函数结合频域维纳滤波器求解去图像模糊的空域反卷积算子。将该方法应用于中巴资源卫星一号 (CBERS 1 )图像 ,图像质量得到明显的提高 。

匀速直线运动模糊的PSF之估计

点扩展函数的设置是影响图像恢复结果好坏的关键问题。对于匀速直线运动模糊 ,要得到好的恢复效果必须能够正确估计模糊范围D和运动模糊方向。在文献 [2 ]中用带最优窗的维纳滤波方法有效地去除了噪声和减小了边缘误差 ,除了边缘的L -形条带外可得到近乎完美的恢复效果 ;并且证明了对任意方向的直线运动模糊图像的恢复只能直接设置二维点扩展函数进行二维恢复 ,不可先进行x方向的一维恢复再进行y方向的一维恢复。该文进一步给出了估计模糊范围D和运动方向的频谱方法 :模糊范围D和图像中心与相邻黑线间的距离u0 成反比 ;运动方向与模糊图像G(u ,v)

基于倒频谱的运动模糊图像PSF参数估计

针对任意方向的直线运动模糊图像，说明只能直接在运动方向上得到运动参数，从而设置二维点扩展函数（point spread function，PSF）。在此基础上，应用倒频谱分析法给出了PSF参数估计的方法。实验表明，该方法在模糊为任意方向且模糊范围介于5～55像素时对参数的估计误差较小，能保证较好的恢复质量；当模糊范围超出该范围时，估计误差急剧加大，估计值不可信，无法保证恢复质量。

运动模糊图像PSF参数估计与图像复原研究

运动模糊图像复原对于改善图像质量有重要的理论意义和现实意义。在研究运动模糊图像复原中,对点扩散函数(PSF)的估计是关键点也是难点。本文利用Radon变换原理来求解点扩散函数PSF中的运动模糊方向,并提出了消除十字亮线引起的干扰的新方法。利用运动模糊图像频谱上的中心暗条纹间距来计算运动模糊尺度。基于估计的PSF参数采用维纳滤波算法来恢复运动模糊图像。实验结果表明,运动模糊参数估计精确,运动模糊方向控制在1°以下,运动模糊尺度控制在1个像素以内。同时采用维纳滤波算法来恢复运动模糊图像,效果优异,可获得细节清晰的图像。

基于航天TDICCD相机像移分析的PSF估计及图像复原算法研究

根据时间延迟积分电荷耦合器件(TDICCD)特殊的工作原理,分析了其产生像移的原因,基于对TDIC-CD像移的分析估计出模糊图像的点扩散函数(PSF)。根据TDICCD像移产生的机理,建立了图像退化的数学模型,并在功率谱均衡复原算法的基础之上提出了像移复原滤波的数学表达式,对运动模糊图像进行了半盲恢复,通过Matlab仿真证明了图像复原算法的可行性和有效性。

锥束CT系统PSF的多孔成像测量与评估方法

针对实际锥束CT系统成像质量退化的问题,提出一种基于多孔成像的方法测量并评估锥束CT系统的点扩展函数(point spread function,PSF)。首先针对平板探测器(flat panel detector,FPD)的PSF进行测量,设计了针孔测量装置,并据此提出一种简便的基于图像恢复的针孔成像PSF测量方法;然后分析了一般条件下锥束CT成像的PSF,提出面向切片图像恢复质量的多孔成像PSF测量与评估方法,并建立了任意直径针孔测量PSF的计算模型。实验结果验证了该方法的可行性,并得到了可恢复出较高质量切片图像的锥束CT系统PSF。

基于谱分析的红外成像模糊去除算法研究

针对红外成像中出现的像差和运动模糊问题,提出了一种基于谱分析的红外成像模糊去除算法。该方法通过对模糊问题的分析,利用红外图像频谱信息构建了模糊函数估计方法,通过数据拟合项和正则项的优化,实现红外图像的模糊去除。实验在运动模糊图像数据集和静态像差图像上进行测试,结果表明:在数据集模糊去除实验上,相比之前的方法,本文方法峰值信噪比(PSNR,peak signal-to-noise ratio)提升了2.01 dB,结果相似性(SSIM,structural similarity index)提升了0.06;静态像差图像在实验室条件下通过短波红外探测器采集,算法在主观上有较明显的复原效果,且针对高通量光学系统成像复原效果更为显著。

新一代帕洛马天文台光谱仪的虚拟刀口欠采样像质测量方法

天文光谱仪的成像质量可用点扩散函数或线扩散函数来表征,但其相对于光谱仪探测器通常为欠采样,很难直接测量。在新一代帕洛马天文台光谱仪的像质测试中引入虚拟刀口法进行光源物面扫描,并应用虚拟刀口法开展欠采样光谱仪像质及光源尺度测量,通过模拟和实验研究,对比分析过采样经典直边刀口法和过采样直接测量方法,验证了虚拟刀口法具有良好的测量精度。在693 nm处,直边刀口法测得光谱仪过采样线扩散函数的半高全宽为7.05μm,虚拟刀口法测量欠采样线扩散函数的半高全宽为7.14μm,测量误差为1.3%。在0.3"视场的光源尺度下,虚拟刀口法测得689、693、701 nm欠采样线扩散函数的半高全宽分别为24.2、27.7、30.8μm,以过采样直接测量结果为参考,其测量准确度分别为98.3%,93.9%和88.8%。实验结果表明,探测器成像严重欠采样时,采用光源物面扫描的虚拟刀口法可准确测量光谱仪的成像质量,该方法结合色散系数还可实现光谱仪分辨率的测量,相关研究工作可为天文光谱仪像质的直接测量提供借鉴。

计算成像技术中的点扩散函数工程

围绕光学成像中点扩散函数(Point spread function,PSF)在计算成像中的新内涵与应用,介绍了传统光学成像中PSF的概念以及PSF在光学系统设计中关键作用,并简要说明了几种利用PSF恢复图像算法以及图像评价指标。在此基础上以计算成像框架下信息传递的视角重新审视了PSF的内涵,从狭义、广义光学系统两个方面对计算成像领域中的相关研究进行了归纳总结,最后展望了PSF工程技术的应用前景及发展趋势。

用于三维单颗粒示踪的多焦面双螺旋点扩散函数显微研究

双螺旋点扩散函数(double-helix point spread function,DH-PSF)显微可实现纳米尺度的三维单颗粒示踪(three-dimensional single particle tracking,3D SPT),被广泛应用于生命科学等领域,但DH-PSF显微的成像景深和定位精度有限,限制了其在活体厚样品中的应用.为了解决此问题,本文提出了一种基于轴向分光棱镜的多焦面DH-PSF显微(z-splitter prism-based multifocus DH-PSF microscopy,ZPMDM)方法和系统,通过将基于轴向分光棱镜的多焦面显微与DH-PSF相结合,在无需扫描的情况下提高DH-PSF显微的轴向定位范围和定位精度,解决完整活细胞内3D SPT的大景深探测难题.通过系统标定,ZPMDM中3个通道的平均三维定位精度分别为σ_(L(x,y,z))=(4.4 nm,4.6 nm,10.5 nm),σ_(M(x,y,z))=(4.3 nm,4.2 nm,8.2 nm),以及σ_(R(x,y,z))=(4.8 nm,4.4 nm,10.3 nm),DH-PSF的有效景深扩展至6μm,实现了大景深范围内的甘油-水混合溶液中的荧光微球示踪,并初步研究了活巨噬细胞的吞噬现象,进一步验证了该方法的有效性,对于3D SPT的发展和应用具有重要意义.