Optimizing imaging parameters for the separation of multiple labels in a fluorescence image

A theoretical analysis is presented on how to separate the contributions from individual, simultaneously present fluorophores in a spectrally resolved image. Equations are derived that allow the calculation of the signal‐to‐noise ratio of the estimates for such contributions, given the spectral information on the individual fluorophores, the excitation wavelengths and intensities, and the number and widths of the spectral detection channels. We then ask how such imaging parameters have to be chosen for optimal fluorophore separation. We optimize the signal‐to‐noise ratio or optimize a newly defined ‘figure of merit’, which is a measure of efficiency in the use of emitted photons. The influence of photobleaching on the resolution and on the choice of imaging parameters is discussed, as well as the additional resolution gained by including fluorescence lifetime information. A surprisingly small number of spectral channels are required for an almost optimal resolution, if the borders of these channels are optimally selected. The detailed consideration of photobleaching is found to be essential, whenever there is significant bleaching. Consideration of fluorescence lifetime information (in addition to spectral information) improves results, particularly when lifetimes differ by more than a factor of two.     

基于子孔径斜率离散采样的波前重构

由于现有评价与测试方法不能满足3~4m地基光电探测系统在不同仰角下对光学系统波前检测的需求,本文提出了基于子孔径斜率离散采样,再重构全口径波面轮廓的波像差测试方法。采用光学模拟与数学分析协同仿真的方法,研究了波面重构算法的不确定度以及扫描运动引起的子孔径倾斜误差、子孔径扫描位置误差、像点坐标测量误差与波前复原精度间的作用规律。仿真结果显示,迭代算法的相对误差ΔPV为0.002 8λ(λ=632.8nm),模式算法的相对误差ΔPV为0.002 7λ。当子孔径倾斜误差小于0.2″,波面重构误差ΔPV约为0.02λ。当子孔径采样位置精度优于0.2mm,其引入的波面重构误差小于0.04nm(PV);当子孔径像点坐标提取精度优于5μm,波面重构误差ΔPV约为0.03λ。研究结果表明,当考虑波面重构过程中的实际测量误差时,模式算法的误差容限较高,收敛性更好。此外,构建实际测试装置时,需引入角度监测与算法误差补偿机制,子孔径倾斜角度监测系统的测角精度需优于0.2″。     

Epifluorescence microscopy study of a quadruple node of triple junctions of grain boundaries in a Eu2+‐doped Kcl:Kbr solid solution by using the doping ion as a fluorochrome

A typical quadruple node (QN) of triple junctions (TJs) of grain boundaries (GBs) in a Eu²⁺‐doped KCl_0.52Br_0.48 solid solution is investigated from the geometrical point of view by epifluorescence microscopy using the doping ion as a fluorochrome. The excitation and fluorescence optical properties of the fluorochrome were previously characterised by spectrophotometry whereas the structural nature of the studied material as well as its Bravais lattice type, unit cell size and long‐range translational order degree was determined by X‐ray diffraction. A three‐dimensional reconstruction was built from the microscopy images of different optical cross‐sections of the studied arrangement of crystal defects. In the close vicinity of the QN, the studied arrangement of crystal defects adopts the geometry of a collapsed tristetrahedron which, centred at the QN, has its legs along the TJs and, hence, has its faces as collapsed in pairs into the GBs. The angles defined by different TJ couples as well as the dihedral angles defined by the different GB couples meeting in every TJ were measured at the QN site. All, the image recording and stacking as well as the measuring procedures are carefully described. The measured TJ angles (97°, 117°, 95°, 117°, 99° and 130° ± 2°) depart from the characteristic angle (109.47°) of a tetrahedron whereas the measured GB angles (101°, 119°, 140°; 125°, 127°, 108°; 133°, 109°, 119°; 129°, 99° and 132° ± 2°) depart from the angular argument (120°) of a 3‐fold symmetry rotation indicating that, in the close neighbourhood of the QN, the studied arrangement of crystal defects is structurally unstable. Such an instability is associated with an observed mismatch in orientation (by angles of 20°, 15°, 33° and 30° ± 2°) between the TJs and some <111> zone axis matrix lattice crystallographic directions ([], [11], [11] and [11]), respectively). Local variations in anionic composition, existing within the solid solution matrix, are discussed to be responsible for this mismatching and, therefore, for the observed structural instability.     

机械振动对光学系统指向精度的影响

针对机械振动对光学系统性能影响的预测问题，基于矩阵光学和机械振动学理论，建立了振动响应对光学系统性能失调和光束稳定性的分析模型，并以某光学系统为例，给出了数值仿真方法。数值结果表明，仿真模型是合理的，可用于预测评价光学平台机械结构设计的优劣。     

基于8PSK 和16PSK 调制的全双工RoF 系统研究

误码率(bit error rate, BER)是信号传输质量的重要衡量指标,为了对比分析8进制相移键控(eight hexadecimal phase shift keying, 8PSK)与16进制相移键控(sixteen hexadecimal phase shift keying, 16PSK)信号的传输性能,建立了一个全双工光载无线通信(radio over fiber, RoF)链路模型。系统的下行链路是对基于马赫增德尔调制器(Maher-Zehnder modulator, MZM)的抑制奇次边带两路信号,分别进行8PSK和16PSK调制。上行链路是取下行链路中一路未被调制的抑制奇次边带信号,作为上行基带信号的载波信号,节约系统的成本。该系统分别在不同的光信噪比(optical signal to noise ratio, OSNR)和不同传输距离条件下,仿真分析了下行链路两种调制信号的光谱图及误码率曲线,通过分析接收信号的星座图和误码特性证明:与16PSK信号相比,当OSNR 25时, 8PSK信号误码率量级可以达到10-4(lg BER-3),当传输距离为40 km时, 8PSK的误码率为4.8×10-3(lg BER=-2.32),仍然可以有效传输数据信息。且在不同OSNR和不同传输距离条件下, 8PSK的误码率均低于16PSK,因此8PSK具有更可靠的传输性能,且更适用于远距离传输。     

Mixing tone mapping operators on the GPU by differential zone mapping based on psychophysical experiments

In this paper, we present a new technique for displaying High Dynamic Range (HDR) images on Low Dynamic Range (LDR) displays in an efficient way on the GPU. The described process has three stages. First, the input image is segmented into luminance zones. Second, the tone mapping operator (TMO) that performs better in each zone is automatically selected. Finally, the resulting tone mapping (TM) outputs for each zone are merged, generating the final LDR output image. To establish the TMO that performs better in each luminance zone we conducted a preliminary psychophysical experiment using a set of HDR images and six different TMOs. We validated our composite technique on several (new) HDR images and conducted a further psychophysical experiment, using an HDR display as the reference that establishes the advantages of our hybrid three-stage approach over a traditional individual TMO. Finally, we present a GPU version, which is perceptually equal to the standard version but with much improved computational performance.     

Growth and characterization of dexterous nonlinear optical material: Dimethyl amino pyridinium 4-nitrophenolate 4-nitrophenol (DMAPNP)

The crystals (dimethyl amino pyridinium 4-nitrophenolate 4-nitrophenol [DMAPNP] suitable for NLO applications were grown by the slow cooling method. The solubility and metastable zone width measurement of DMAPNP specimen was studied. The material crystallizes in the orthorhombic crystal system with noncentrosymmetric space group of P2₁2₁2_1. The ocular precision in the intact visible region was found to be good for non-linear optical claim. Quality of the grown crystal is ascertained by the HRXRD and etching studies. Laser Damage Threshold and Photoluminescence studies designate that the grown crystal contains less imperfection. The mechanical behaviour of DMAPNP sample at different temperatures was investigated to determine the hardness stability of the grown specimen. The piezoelectric temperament and the relative Second Harmonic Generation (for diverse particle sizes) of the material were also studied. The third order nonlinear optical properties of DMAPNP crystals were premeditated by Z-scan method. Birefringence and optical homogeneity of the crystal were evaluated using modified channel spectrum method. The half wave voltage of the grown crystal deliberate from the elector optic experimentation. Photoconductivity measurement specified consummate of inducing dipoles owing to brawny incident radiation and also disclose the nonlinear activities of the grown specimen.     

Screening efficiency of the Hardy–Rand–Rittler (HRR) colour test (4th edn)

This study evaluates the screening efficiency of the Hardy–Rand–Rittler (HRR) 4th edition colour test. This test was also compared with results from the Ishihara test. Thirty-nine subjects with congenital red–green deficiency and 120 colour normal subjects participated in the study. The subjects were shown the Ishihara (concise version, 2001) and the HRR (4th edn) pseudoisochromatic plates. Each plate was viewed for 3?s. A Macbeth Easel lamp was used for illumination (70?foot-candle). The HRR test had 100% sensitivity and the specificity was 63%. The overall efficiency of the HRR test was less than that of the Ishihara. The results also indicated that plate seven of HRR (4th edn) has poor screening efficiency. Thus the HRR is good for identifying colour deficient subjects but a caveat is that it fails too many normals.     

Microwave diversity imaging system ‐ principle,methodology and experimental results

Abstract

The basic principle, methodology and experimental results of the automated microwave diversity imaging system developed in the Electromagnetic Research Laboratory of National Taiwan University are presented. The microwave image formulation is based on Bojarski's identity. In practice, accessing the object backscattering information using the frequency, angular and polarization diversity techniques is conducted by the developed microwave measurement system with major parts including dual polarization antennas, network analyzer and a MicroVax III. It is shown that images of a scale model of the space shuttle reconstructed from the measured data can be identified visually. The implications for high‐resolution microwave imaging radar networks are also discussed.