Analysis of displacement damage effects on the charge-coupled device induced by neutrons at Back-n in the China Spallation Neutron Source

Displacement damage effects on the charge-coupled device(CCD)induced by neutrons at the back-streaming white neutron source(Back-n)in the China Spallation Neutron Source(CSNS)are analyzed according to an online irradiation experiment.The hot pixels,random telegraph signal(RTS),mean dark signal,dark current and dark signal non-uniformity(DSNU)induced by Back-n are presented.The dark current is calculated according to the mean dark signal at various integration times.The single-particle displacement damage and transient response are also observed based on the online measurement data.The trends of hot pixels,mean dark signal,DSNU and RTS degradation are related to the integration time and irradiation fluence.The mean dark signal,dark current and DSNU2 are nearly linear with neutron irradiation fluence when nearly all the pixels do not reach saturation.In addition,the mechanisms of the displacement damage effects on the CCD are demonstrated by combining the experimental results and technology computer-aided design(TCAD)simulation.Radiation-induced traps in the space charge region of the CCD will act as generation/recombination centers of electron-hole pairs,leading to an increase in the dark signal.

Detailed characterization of polycapillary focusing x-ray lenses by a charge-coupled device detector and a pinhole

A method to measure the detailed performance of polycapillary x-ray optics by a pinhole and charge coupled device(CCD)detector was proposed in this study.The pinhole was located between the x-ray source and the polycapillary x-ray optics to determine the illuminating region of the incident x-ray beam on the input side of the optics.The CCD detector placed downstream of the polycapillary x-ray optics ensured that the incident x-ray beam controlled by the pinhole irradiated a specific region of the input surface of the optics.The intensity of the output beam of the polycapillary x-ray optics was obtained from the far-field image of the output beam of the optics captured by CCD detector.As an application example,the focal spot size,gain in power density,transmission efficiency,and beam divergence of different parts of a polycapillary focusing x-ray lenses(PFXRL)were measured by a pinhole and CCD detector.Three pinholes with diameters of 500,1000,and 2000μm were used to adjust the diameter of the incident x-ray beam illuminating the PFXRL from 500μm to the entire surface of the input side of the PFXRL.The focal spot size of the PFXRL,gain in power density,transmission efficiency,and beam divergence ranged from 27.1μm to 34.6μm,400 to 3460,26.70%to 5.38%,and 16.8 mrad to 84.86 mrad,respectively.

Investigating the Thermal Stress of Millisecond Pulsed Laser Irradiation on Charge-Coupled Devices

In this study, a two-dimensional model describing thermal stress on a charge-coupled device (CCD) induced by ms laser pulses was examined. Considering the nonlinearity of the CCD’s material parameters and the melting phase transition process of aluminum electrode materials was considered by using equivalent specific heat capacity method, the physical process where a laser pulse irradiating a CCD pixel array was simulated using COMSOL Multiphysics software. The temperature field and thermal stress field were calculated and analyzed. In order to clarify the mechanism producing damage on the CCD detector, Raman spectra from silicon were measured with a micro-Raman spectrometer to determine stress change in the CCD chip. The procedure presented herein illustrates a method for evaluating strain in a CCD after laser irradiation.

The nonlinearity measurement of charge-coupled device array spectrometer using colorful LED

A nonlinearity measurement of the charge-coupled device(CCD) array spectrometer using flux addition and comparison method is described. The light with various colors from the colorful light emitting diode(LED) light source is applied to measure the nonlinearity of the spectrometer at different wavelengths, respectively. An high-end CCD array spectrometer is tested. For colorful LED light sources, the nonlinearity factors of the CCD array spectrometer(absolute value) are as follows: k<0.8% for white light, k <1.1% for red light, k <2.2% for green light and k<4.7% for blue light. By using those quasi-monochromatic light sources, it is shown that the nonlinearity depends on the wavelength. It is important to be wariness about the spectral nonlinearity and related uncertainty evaluation when the narrow-band light source is tested.

Origin of peculiar inerratic diffraction patterns recorded by charge-coupled device cameras

A peculiar and regular diffraction pattern is recorded while using either a color or a monochrome charge-coupled device (CCD) camera to capture the image of the micro air plasma produced by femtosecond laser pulses. The diffraction pattern strongly disturbs the observation of the air plasma, so the origin and eliminating method of these diffraction patterns must be investigated. It is found that the Fourier transform of the periodic surface structure of either the mask mosaic of the color CCD or the pixel array of the monochrome CCD is responsible for the formation of the observed pattern. The residual surface reflection from the protection window of a CCD camera plays the essential role in forming the interesting two- dimensional diffraction spots on the same CCD sensor. Both experimental data and theoretical analyses confirm our understanding of this phenomenon. Therefore remov-ing the protection window of the CCD camera can eliminate these diffraction patterns.

CCD摄像机镜头薄棱镜畸变的研究

本文以CCD摄像机小孔成像模型为基础建立了薄棱镜畸变的非线性几何畸变模型,通过对影响畸变参数测量精度的各种因素的分析,使用最小二乘法解线性方程组得到摄像机系统畸变模型的畸变系数。通过与径向畸变相对比得出薄棱镜畸变对摄像机标定的影响相对较小,在此基础上提出了提高标定精度的有效方案。

针-板电极空气隙直流放电光信息采集

为研究气体击穿的放电机理,采集直流电压下针-板电极空气隙流注放电击穿瞬间的光信号,实验设计了气体放电光学采集装置.利用光纤,光谱仪和ICCD组成光信号检测系统,其中ICCD单独使用可以捕捉光现象,配合光谱仪可采集光谱.实验中采用具有高速触发脉冲的外部触发方式操作控制器,进行图像及光谱的采集,并对采集到的结果进行分析和讨论.

空间CCD图像传感器辐射损伤评估方法

CCD图像传感器作为高灵敏度光电集成部件,易受空间辐射的影响而发生性能退化和工作异常。开展其辐射效应评价研究并制定相应的防护对策,是保证其在空间可靠应用的前提。文章通过地面模拟试验和辐射屏蔽计算,对空间用CCD图像传感器电离辐射损伤与位移损伤效应开展评估方法研究,为CCD抗辐射加固设计与地面评估试验提供参考。该方法也可用于其他光电器件和材料辐射效应评价。

ONLINE GRINDING WHEEL WEAR COMPENSATION BY IMAGE BASED MEASURING TECHNIQUES

Automatic compensation of grinding wheel wear in dry grinding is accomplished by an image based online measurement method. A kind of PC-based charge-coupled device image recognition system is schemed out, which detects the topography changes of the grinding wheel surface. Profile data, which corresponds to the wear and the topography, is measured by using a digital image processing method. The grinding wheel wear is evalualed by analyzing the position deviation of the grinding wheel edge. The online wear compensation is achieved according to the measure results. The precise detection and automatic compensation system is integrated into an open structure CNC curve grinding machine. A practical application is carried out to fulfil the precision curve grinding. The experimental results confirm the benefits of the proposed techniques, and the online detection accuracy is less than 5 um. The grinding machine provides higher precision according to the in-process grinding wheel error compensation.

Simulation study on reconstruction model of three-dimensional temperature distribution within visible range in furnace

This paper presents a reconstruction model of three-dimensional temperature distribution in furnace based on radiative energy images captured by charge-coupled device （CCD） cameras within the visible wavelength range. Numerical simulation case was used in this study and a zigzag eccentric temperature distribution was assumed to verify the model. Least square QR-factorization （LSQR） method was introduced to deal with reconstruction equation. It is found that the reconstructed temperature distributions in low-temperature areas had some fluctuations and high-temperature areas were reconstructed well. The whole reconstruction relative error was mainly due to errors in low-temperature areas and the relative error for highest-temperature reconstruction was quite small.

CCD signal acquisition and optimal digital denoise technology

To reduce the charge-coupled device(CCD)readout noise and improve the detection ability under low illumination and dim targets,a new low-noise CCD signal processing technology-CCD digital denoiseis gradually being employed in aerospace detection and other fields.In this study,the main readout noise of CCD detectors and its characteristics are analyzed.A CCD digital denoise system and an experimental platform are designed as well as established by using a PCIe data acquisition card.According to the characteristics of readout noise,some digital filters are analyzed and designed based on distributed kernel coefficient,and the optimal kernel coefficients are obtained through iteration.Then,CCD signal and filter model are established,and the optimal filter is designed to apply to the digital denoise system.Finally,according to the image data obtained from the system,the performance of the digital denoise system and digital filtering algorithm is evaluated and compared.At 500 kHz and 1 MHz CCD readout rates,the denoising performance of the optimal filter designed in the experiment is 16%-32%higher than that of the digital filter with kernel distribution coefficient,and 50%-60%higher than that of the traditional correlated double sampling technology.

物证检验照相中噪点的产生原因及解决方案

数码相机的噪点影响了照片成像质量,给数码相片进行物证检验、作为诉讼证据使用、进行网络传输等都带来了不利因素,文章分析了噪点产生的原因,并提出了解决方案．

Preliminary Study of CAS-LIBB Single-Particle MicrobeamⅡEndstation:Ⅱ.Considerations for Choosing the Right CCD Camera

The proposed multi-dimensional quantitative fluorescence microscopy for the CASLIBB single-particle microbeam II endstation is a CCD-based imaging system. We systematically analyse the theoretical and the practical considerations pertinent to choosing the right CCD camera and unveiling the principles underlying multifarious parameters. Therefore, this analysis can be a valuable tool in scrutinizing each parameter and clarifying proper usage of a scientific CCD camera.

Modified BB84 Protocol Using CCD Technology

Quantum cryptography and especially quantum key distribution (QKD) is a technique that allocates secure keys only for a short distance. QKD protocols establish secure key by consent of both the sender and receiver. However, communication has to take place via an authenticate channel. Without this channel, QKD is vulnerable to man-in-the-middle attack. While not completely secure, it offers huge advantages over traditional methods by the use of entanglement swapping and quantum teleportation. In our research, we adopt the principle of charge-coupled device (CCD) to transfer the qubit from the sender to the receiver via a quantum channel. This technology has an added advantage over polarizer as only the circuit for transmitting the qubit is sufficient. No extra circuitry to implement the polarizer is required.

Development of a rapid measurement system for coarse aggregate morphological parameters

Morphological parameters of coarse aggregates,including the angularity index (Al),flat and elongated ratio,flatness ratio,and sphericity,strongly affect the performance of asphalt concrete.A device must be developed to efficiently and accurately measure these parameters.Herein,a charge-coupled device camera and a linear profile scanner are combined to evaluate the parameters.The Al is calculated using three methods.The results show that the fitted-ellipse method provides superior results among the three Al measurement methods.Moreover,the use of a linear profile scanner improves the Al measurement accuracy.Therefore,the proposed combination has high measurement efficiency and is suitable for batch inspections.

A digital CDS technique and its performance testing

Readout noise is a critical parameter for characterizing the performance of charge-coupled devices（CCDs）, which can be greatly reduced by the correlated double sampling（CDS） circuit. However, a conventional CDS circuit inevitably introduces new noise since it consists of several active analog components such as operational amplifiers. This paper proposes a digital CDS circuit technique, which transforms the pre-amplified CCD signal into a train of digital presentations by a high-speed data acquisition card directly without the noisy CDS circuit,then implements the digital CDS algorithm through a numerical method. A readout noise of 3.3 e- and an energy resolution of 121 e V@5.9 ke V can be achieved via the digital CDS technique.

A Novel Multi-Points Laser Monitoring of Building Settlement and Its Risk Evaluation

Aiming at the defects of routine settlement measurement methods, such as complicated procedures, time-consuming and labor-intensive, high cost and low measurement accuracy, based on the analysis of existing engineering measurement technical requirements and specifications, a multi-point high precision and high efficiency based on laser reference is proposed. The automatic building settlement real-time monitoring system program gives the principle and system model of single-point settlement observation. The model of multi-point scanning settlement monitoring system and the model of multi-point network settlement monitoring system are designed, and their advantages and disadvantages are analyzed. We focus on the networked multi-point settlement monitoring system for network cumulative error analysis, and propose related evaluation and correction methods. The hardware schematic and software block diagram of the laser reference measurement and measurement system of the single point settlement acquisition system are given. Finally, the risk of subsidence state is quantitatively evaluated based on multi-point settlement monitoring data. The measurement error of this method is less than 300 μm, which can realize the monitoring and evaluation of the overall settlement.

Fabrication and characterization of annealed proton exchanged long period waveguide grating in x-cut LiNbO3

In this paper, a long-period waveguide grating was fabricated in x-cut lithium niobate substrate by patterned annealed proton exchange waveguide fabrication process. The waveguide mode characteristic was evaluated using a charge-coupled device(CCD) camera. It shows that the waveguide is single mode transmission at a wavelength of1 550 nm. The transmission spectra of the long period waveguide gratings were measured by optical spectrum analyzer(OSA) and show an extinction ratio of ~17 dB and a 3 dB bandwidth of ~10 nm at the resonant wavelength. The resonant wavelength moves toward to the long wavelength direction as the waveguide width-difference increases in the same period, and also shifts toward to the long wavelength direction with the increase of the period in the case of the same waveguide width-difference. The method of fabricating a long period waveguide grating based on a patterned annealed proton exchange technique simplifies the fabrication process, and at the same time, reduces the fabrication cost.