异步Binning高帧频CCD相机的拖尾校正

一种基于异步时序驱动和Binning技术的高帧频成像技术在帧转移CCD相机上得到成功应用。为了抑制该CCD相机成像时产生的拖尾效应,基于该相机的高帧频连续成像原理,理论上分析了图像获取过程中拖尾产生的原因,给出了一套完整的消除拖尾的数值解析算法。该算法充分考虑了图像亮度变化对拖尾形成产生的影响,并对此进行了修正,已在异步Binning CCD相机上进行了实验验证。利用相机以40 000帧每秒的帧频获取4幅连续图像进行实验,实验结果表明,该算法可有效去除每幅图像的拖尾噪声,而且消除拖尾噪声后的图像区域的灰度方差得到明显降低,异步Binning CCD相机的成像质量得以提高。上述结果表明算法适用于高帧频相机的连续成像。     

大面阵CCD图像实时显示系统的设计

为解决基于CameraLink接口的相机必须使用专用采集卡和系统机才能显示的问题,设计了一种结构简单、携带方便的图像实时显示系统。该系统采用2片SDRAM对图像进行交替缓存,并在Xilinx公司的Spatan3系列现场可编程门阵列(FPGA)中完成了较为复杂的主要控制逻辑。将CameraLink输入的图像经过拼接、BIN等预处理后缓存到1片SDRAM,同时按照一定格式以25frame(50field)/s的速度读出另1片SDRAM中的图像,经ADV7300转换成模拟电视信号后送到模拟显示器显示。结果表明,在相机帧频为3.6frame/s时,该系统可以实时显示大面阵CCD数字航测相机拍摄的图像,能观察不同分辨率的图像以及原图像任何部位的细节,并能根据天气条件调整显示亮度以更好地观察图像。该系统只包含1块电路板和1个模拟显示器,已成功应用于4008×5344面阵的CCD数字航测相机中。     

Multiport-readout frame-transfer 5 megapixel CCD imaging system for TEM applications

A multiport-readout, frame-transfer charge-coupled device (CCD) digital imaging system has been successfully developed and tested for intermediate-high-voltage electron microscopy (IVEM) applications up to 400 keV. The system employs a back-thinned CCD with 2560 x 1960 pixels and a pixel size of 24 microm x 24 microm. In the current implementation, four of the eight on-chip readout ports are used in parallel each operating at a pixel rate of 1- or 2-MHz so that the entire CCD array can be read out in as short as 0.6 s. The frame-transfer readout functions as an electronic shutter which permits the rapid transfer of charges in the active pixels to four masked buffers where the charges are readout and digitized while the active area of the CCD is integrating the next frame. With a thin film-based phosphor screen and a high-performance lens relay, the system has a conversion factor of 2.1 digital units per incident electron at 400 keV, and a modulation transfer function value of 14% at the Nyquist frequency.     

中阶梯光栅光谱仪CCD相机的设计

为了高精度采集中阶梯光栅光谱仪的谱图,设计了一种适用于中阶梯光栅光谱仪原理样机的高性能面阵CCD相机。首先,根据中阶梯光栅光谱仪的谱图特点和CCD芯片的特性,设计了面阵CCD相机的时序产生电路、驱动电路及数据采集处理电路,实现了面阵CCD相机的低噪声、高灵敏度以及高动态范围。然后,利用LabVIEW编写了CCD相机测试软件。最后,利用设计的面阵CCD相机对汞灯谱线进行了测试。结果表明:面阵CCD相机获取的二维谱图图像清晰、信噪比较高;经二维谱图还原后,可以得到标准的汞灯谱线。该相机性能稳定、可靠,满足中阶梯光栅光谱仪原理样机的研制要求。     

CCD显微摄像法测量孔心距

通过对 1 9J型万能工具显微镜进行数码改造 ,建立了用于工件孔心距测量的CCD数码显微摄像系统。讨论了CCD摄像法测量孔心距的基本原理 ,简要介绍其软件系统 ,为工件孔心距的精密测量提供了快速、有效、经济的测量途径。     

高分辨率CCD芯片FTF4052M的驱动系统设计

CCD芯片的驱动系统是数字航测相机的核心部分,它关系到整个相机的性能和技术指标。介绍了高分辨率全帧CCD芯片FTF4052M的内部结构和驱动时序,采用集成芯片设计了该CCD芯片的驱动电路并应用于数字航测相机系统,其中包括驱动电路的时序设计和所需偏置电源的设计。集成芯片SAA8103为驱动CCD芯片提供脉冲信号,与TDA9991协调工作产生CCD垂直行驱动时钟,与74ACT04芯片配合产生驱动CCD芯片的水平像素转移时钟。实验结果表明,此CCD驱动系统采用大规模专用集成芯片进行设计,具有性能好,功耗低,体积小的优点,能够输出两路CCD电压信号,数据输出速率达2帧/s,满足了数字航测相机系统的设计要求。     

A method to determine long-range order parameters from electron diffraction intensities detected by a CCD camera

To determine long-range order parameters from electron diffraction intensities, the authors have developed a CCD camera system to detect precisely electron diffraction intensities, a method for quickly and precisely measuring specimen thickness, and a computer programming to calculate long-range order parameters from the ratio of superlattice and fundamental diffraction intensities. Thickness variation over a diffraction area is taken into consideration in the calculation of electron diffraction intensities on the basis of the multi-slice method, and long-range order parameters are calculated by the successive approximation method. The absorptive form factors are also calculated from experimental data of diffraction intensities by parameter fitting, and the effect of absorption on the calculation of long-range order parameters is examined. The values of Cu(3)Au alloys aged at 523 and 653 K that were obtained by averaging long-range order parameters determined for several diffraction areas with the developed method are close to the reported data obtained by the X-ray diffraction method. The main causes for the deviation of long-range order parameters determined for several diffraction areas are also discussed.     

用作图法判定航空相机TDI CCD积分方向

由于Time Delay and Integration CCD(TDI CCD)是一种类似面阵结构的线阵输出CCD,其光电荷转移具有一定的方向性,所以TDI CCD图像传感器的积分方向与CCD成像运动方向必须保持一定的关系才能成像。本文以推扫成像相机和摆扫成像相机为例,介绍了一种基于高斯成像原理的作图法,用以确定TDI CCD积分方向与传感器成像运动方向的关系,分析和论证表明,TDI CCD的积分方向必须与地物在像面上的像移方向一致。 实践证明这种方法可以清楚、简便、快速地确定TDI CCD的积分方向,从而确定TDI CCD的安装方向,适宜在实际的工程设计中采用。     

Characterisation of the signal and noise transfer of CCD cameras for electron detection

Methods to characterise the performance of CCD cameras for electron detection are investigated with particular emphasis on the difference between the transfer of signal and noise. Similar to the Modulation Transfer Function MTF, which describes the spatial frequency dependent attenuation of contrast in the image, we introduce a Noise Transfer Function NTF that describes the transfer of the Poisson noise that is inevitably present in any electron image. A general model for signal and noise transfer by an image converter is provided. This allows the calculation of MTF and NTF from Monte-Carlo simulations of the trajectories of electrons and photons in the scintillator and the optical coupling of the camera. Furthermore, accurate methods to measure the modulation and noise transfer functions experimentally are presented. The spatial-frequency dependent Detection Quantum Efficiency DQE, an important figure of merit of the camera which has so far not been measured experimentally, can be obtained from the measured MTF and NTF. The experimental results are in good agreement with the simulations and show that the NTF at high spatial frequencies is in some cases by a factor of four higher than the MTF. This implies that the noise method, which is frequently used to measure the MTF, but in fact measures the NTF, gives over-optimistic results. Furthermore, the spatial frequency dependent DQE is lower than previously assumed.     

Noise in off-axis type holograms including reconstruction and CCD camera parameters

Phase and amplitude images as contained in digital holograms are commonly extracted via a process called “reconstruction”. Expressions for the expected noise in these images have been given in the past by several authors; however, the effect of the actual reconstruction process has not been fully appreciated. By starting with the Quantum Mechanical intensity distribution of the off-axis type interference pattern, then building the digital hologram on an electron-by-electron base while simultaneously reconstructing the phase/amplitude images and evaluating their noise levels, an expression is derived that consistently describes the noise in simulated and experimental phase/amplitude images and contains the reconstruction parameters. Because of the necessity to discretize the intensity distribution function, the digitization effects of an ideal CCD camera had to be included. Subsequently, this allowed a comparison between real and simulated holograms which then led to a comparison between the performance of an “ideal” CCD camera versus a real device. It was concluded that significant improvement of the phase and amplitude noise may be obtained if CCD cameras were optimized for digitizing intensity distributions at low sampling rates.     

基于高斯拟合测量CCD灵敏度均匀性

在精密度要求较高的图像测量领域中,CCD灵敏度的不均匀对测量精度有较大的影响。因此,提出了一种基于小孔衍射原理的高斯曲面拟合像面光场测量CCD灵敏度均匀性的方法。由于CCD自身的物理结构设计不均匀性、响应非线性以及暗电流等噪声因素使得光响应偏离实际值,该方法通过对CCD像面上感兴趣光场域进行高斯曲面拟合来确定零点像素的灰度响应。对所有像素测量完成之后通过归一化即可计算出CCD灵敏度均匀性。实验结果表明:对所使用的CCD47-10系列,计算其CCD灵敏度均匀性为2.14%。该测量方法基本满足设计原理简单、稳定性可靠、抗干扰能力强的要求,完成了快速、自动测量。     

Noise in off-axis type holograms including reconstruction- and CCD camera parameters

Phase and amplitude images as contained in digital holograms are commonly extracted via a process called “reconstruction.” Expressions for the expected noise in these images have been given in the past by several authors; however, the effect of the actual reconstruction process has not been fully appreciated. By starting with the Quantum Mechanical intensity distribution of the off-axis type interference pattern, then building the digital hologram on an electron-by-electron base while simultaneously reconstructing the phase/amplitude images and evaluating their noise levels, an expression is derived that consistently describes the noise in simulated and experimental phase/amplitude images and contains the reconstruction parameters. Because of the necessity to discretize the intensity distribution function, the digitization effects of an ideal CCD camera had to be included. Subsequently, this allowed a comparison between real and simulated holograms which then led to a comparison between the performance of an “ideal” CCD camera versus a real device. It was concluded that significant improvement of the phase and amplitude noise may be obtained if CCD cameras were optimized for digitizing intensity distributions at low sampling rates.     

TDICCD相机的实验与研究

目前,CCD已被广泛地应用于各个领域。这里,我们介绍一种特殊的线阵CCD相机,它应用时间延迟积分(TDI)技术,可在低光照情况下,获得高灵敏度、高输出速率、高空间分辨率和大的动态范围。为了应用TDI方式及验证它的效果,我们使用加拿大DALSA公司生产的CT-E12048×96TDI线阵CCD相机,设计制作了一套完整的系统,并做了捕获运动图像的实验。该系统包括:相机、相机控制器、图像捕获器、微机和转台。实验结果表明:当CCD相机的行转移速率和物体的运动速率不同步时,不能够获得清晰的图像。而当我们使用相移补偿技术,使两个速率相匹配后,得到了非常清晰的图像。     

Pyrometry using CCD cameras

The method of measurement of the surface brightness temperature distribution in high-enthalpy wind tunnels using CCD cameras is described. The problems of the operating wavelength selection, CCD camera metrology, and camera calibration by a black body and temperature lamps, as well as the possibility of LED reference etalon usage for correction of optical channel transmission variation are discussed. It is proposed to measure the emission spectrum of the surface under investigation for brightness pyrometry validation and for surface emissivity evaluation.     

高速CCD图像数据光纤传输系统

本文提出了一种多路高速CCD图像数据光纤并行传输系统,并应用于空间遥感相机中。设计并实现了单路有效数据率最高可达1.28Gbps的光纤传输通道。阐述了系统设计思想,光纤传输通道结构,并对其中的关键技术高速总线接口、高速串行光电接口等进行了详细分析。实际完成了5通道TDICCD图像数据光纤并行传输系统,总有效数据率高达5.7Gbps。通过实验证明该系统工作稳定可靠,实时传输效果好,无误码,满足了高速多通道CCD图像数据的高速率,远距离传输要求。     

CCD图像灰度与照度的转换标定方法

本文提出了一种基于CCD摄像机利用图像灰度获得实际照度的新方法,该方法适用于摄像机的任意曝光和增益参数,且考虑了摄像机安装位置和角度对测量的影响。CCD摄像机照度测量法的实际应用主要涉及两个过程:一是标定过程,即应用CCD摄像机进行照度测量前,标定CCD图像灰度与照度之间的转换参数和转换模型;二是照度测量过程,即通过CCD摄像机拍摄图像,将图像灰度代入已定的转换模型,获得测量对象的照度值。其中,灰度与照度转换模型的标定是利用CCD摄像机实现照度测量的基础和关键,文中主要讨论了该模型的推导过程以及标定方法。具体为:首先通过理论推导获得图像灰度与CCD传感器感应的相对辐照度的关系,然后借助以均匀光源搭建的实验系统标定CCD传感器相对辐照度与物面实际照度之间的关系,进而获得图像灰度与物面实际照度的转换关系。在转换过程中讨论了曝光时间、增益以及CCD相机与照度测量点之间的距离和角度对转换模型的影响,为CCD摄像机照度测量法的实际应用奠定了基础。实验结果表明本测量及标定方法适用于摄像机任意曝光和增益条件,经过本方法标定后,应用CCD摄像机进行照度测量,测量结果的相对误差在4.5%以内。     

CCD摄像机快速标定技术

在视觉检测系统中,针对视觉传感器数量多,且每个摄像机需标定的内部参数及外部参数较多的特点,提出了一种新的简单的快速摄像机标定方法.分析了摄像机的各个关键参数,采用了全线性标定方法和矢量分析法,逐步求出CCD摄像机的参数.该方法具有标定速度快、精度较高、实用和算法性能分析容易等优点,适用于一般视觉检测系统的摄像机参数的标定,尤其是大型视觉检测系统中多视觉传感器的摄像机参数的标定.实际结果表明,摄像机标定误差优于0.05mm.     

小波神经网络在CCD图像噪声处理中的应用

目的：CCD相机响应功能的非线性,导致了CCD噪声模型的复杂性,使得滤波效果不佳,本文提出一种针对于数字图像中CCD噪声的小波神经网络滤波器。方法：首先,分析CCD噪声模型,找出导致CCD噪声模型复杂的原因——CCD相机响应功能（camera response function简称CRF）的非线性;接着,在对ANS滤波器分析的基础上,针对影响滤波效果的两大问题：滤波窗口和图像强度,将小波神经网络非线性逼近CCD噪声曲线,按照噪声参数对图像进行区域划分并分配相应的权值,然后结合相应的非线性滤波器进行针对性滤波,最后综合输出。结果：实验结果表明：本文改进的滤波器滤波效果明显,信噪比得到进一步提高（24.65）。结论：利用神经网络良好的非线性函数逼近性,将其结合ANS滤波器构造出神经网络非线性ANS滤波器（NN-NANS filter）,试验结果表明,该滤波器在去除噪声的同时边缘细节也得到了很好的保留,同时提高了信噪比。     

利用普通CCD实现百万帧/秒超高速成像的时序驱动技术

提出了基于普通CCD的掩模式成像技术来大幅提高CCD的图像获取速度,实现百万帧/秒的CCD时序驱动方法。介绍了加掩模后CCD的工作过程,利用掩模把普通CCD的光敏区划分为带有存储区的像素阵列,实现了普通CCD的片上存储功能。分析了利用普通CCD实现百万帧/秒超高帧频的时序驱动方法,掩模形状决定了帧速,帧数和图像的分辨率。对系统的时序结构、电荷转移方式和驱动电路进行了说明,通过特殊驱动电路和图像处理软件设计实现了百万帧/秒的超高帧频。最后,对驱动时序进行了仿真和实验验证。采用条状孔阵列掩模,基于普通CCD图像传感器进行了百万帧/秒工作速度的验证,获得了14幅79pixel×79pixel的图像,其帧频达到200×104 frame/s。文章所述技术具有一定的通用性。     

采用外触发方式实现CCD摄像机的全自动调光控制

针对传统的CCD摄像系统自动调光方法在工程使用中存在的不足,提出一种新型的CCD摄像系统的全自动调光方法。它采用外触发电子快门和可变光阑相组合进行调光,外触发电子快门调光为主,可变光阑调光为辅。采用外触发方式实现CCD摄像机的电子快门时间调节,由单片机控制电机调节可变光阑的通光口径,以使像面照度适中。反馈控制量由图像目标区域的均值电平获得,从而实现最佳全自动调光。简要叙述了新型调光系统的组成和工作原理。Matlab仿真结果表明,与传统调光方法相比,新型调光方法调光拍摄的图像对应的直方图分布更宽广且更均匀,功率谱幅值也更高,达到7.5dB以上。其图像更清晰,对比度更高,目标层次对比也更加明显,满足现代CCD摄像系统的最佳全自动调光要求。