【作者】 何伟基；

【导师】 陈钱；

【作者基本信息】 南京理工大学 ， 光学工程， 2009， 博士

【摘要】 电子倍增CCD采用碰撞电离机制实现了光生电荷信号在固态器件内的放大倍增,实现了器件的全固态化,是微光成像技术重点发展的关键技术之一。本论文在归纳总结普通CCD工作原理及其在微弱光成像应用方面的不足,重点分析电子倍增CCD中电荷倍增寄存器实现电荷倍增的原理,提出了电荷倍增的数学模型,讨论了微弱光环境中电荷倍增对电子倍增CCD成像的影响,创新性的提出了基于单光子响应模型的双重阈值原理,克服了常态制冷状态下暗电流噪声对电子倍增CCD单光子探测性能的影响,使得采用低成本半导体制冷的电子倍增CCD可以实现光子计数成像。本文的研究内容主要包括普通CCD工作原理、电荷倍增机制及其模型、电子倍增CCD成像模型、基于电子倍增CCD的光子计数成像原理以及电子倍增CCD的测试分析实验装置的建立和试验。通过对电子倍增CCD工作机制及其在光子计数成像的应用研究,可以为我国实现电子倍增CCD核心技术自主化提供理论依据,为尽快突破英美发达国家的技术封锁贡献力量。在CCD工作原理研究方面,本文重点对埋层沟道CCD器件内的二维电势场分布进行了研究。通过求解一维泊松方程和传输线波动方程,得到了埋层沟道CCD的二维电势场分布的解析表达式,分析了电极间中心距、电极偏置电压和电极内存储电荷容量等关键因素对二维电势场分布的影响,明确了埋层沟道CCD器件内的二维电势场分布。电荷倍增寄存器实现电荷倍增的原理研究方面,本文重点分析了电荷倍增寄存器实现电荷倍增的四个要点：强电场、大电荷势阱容量、溢出控制器和直流偏置相。同时,依据电荷倍增过程是否具备Markov性,本文将电荷倍增过程分为两种模式：高增益模式和普通增益模式。在不同模式下,分别通过求解Markov-扩散方程和Malthusian方程得到倍增寄存器的增益统计特性、增益期望和方差和增益概率密度函数。利用搭建的电子倍增CCD测试系统发现,除了倍增电极的偏置电压外,倍增电极内信号电荷包的大小也影响到电子倍增CCD的电荷倍增过程。在电子倍增CCD成像模型研究方面,本文通过建立电子倍增CCD的电荷转移模型和器件模型,得到了电子倍增CCD的系统响应函数和幅频响应特性,并分析了电荷倍增过程对成像的影响。借助于实验测试可知：尽管电荷倍增过程并没有改变电子倍增CCD的幅频响应的分布特征,但是由于电荷倍增过程提高了响应幅度,电荷倍增过程可以有效提高电子倍增CCD在低照度条件下的细节分辨力。在基于电子倍增CCD的光子计数成像研究方面,本文通过离散单光子响应模型得到了判断电子倍增CCD是否满足单光子探测的依据。借助于电子倍增CCD的单光子响应模型,讨论并分析了利用双重阈值方法实现光子事件检测的原理,并给出了幅度闽值和频率闽值选择的依据。通过单光子探测效率与误差实验,本论文分析了电子倍增CCD在光子计数成像模式下的性能。通过光子计数成像实验测试证明：采用光子计数模式,电子倍增CCD的最小响应度可以达到0.1个电荷／像素／帧,明显优于相同情形下的其他成像方式的结果。本文研究工作受到部委科研项目"XXXXXX成像技术(4040508011)”、部委科研项目"XXXXXXXXXXX成像技术研究(A2620060242)”和江苏省自然科学基金项目“光子计数成像机理及其关键技术研究(BK2008049)”的支持。更多还原

【Abstract】 Adopting the impact ionization mechanism, EMCCD (Electron Multiplication CCD) achieved the multiplication of photo-generated charge signals in solid-state devices, and achieved all solid-state technology of devices. It is one of the key technologies of low-light imaging technology. Based on the summary of traditional CCD working principle and its deficient in low-light imaging application, it analyzed charge multiplication working principle of charge multiplication register in EMCCD, put forward mathematical model of charge multiplication, discussed the effect of charge multiplication on EMCCD imaging in low-light environment, innovatively proposes the dual-threshold principle of single-photon response model, and overcame the effect of dark current noise on single-photon detection performance of EMCCD in normal cooling condition, so that we could adopt the EMCCD to achieve photon counting imaging using low-cost thermal electrical refrigerator. The main contents of this paper studied the traditional CCD working principle, charge multiplication mechanism and model, imaging model of EMCCD, photon counting imaging principle based on EMCCD, and the experimental equipments build and experiments of EMCCD tests. Through the research on EMCCD working and its application in photon counting imaging, we could offer the theoretical basis for achieving the independence of EMCCD core technologies, so as to make some contributions to break through the technology blockage of United Kingdom and American developed countries as soon as possible.On the aspect of research on CCD working principle, it mainly studied the two-dimensional electric potential field distribution in buried-channel CCD device. Through the solutions of one-dimensional Poisson’s equation and wave equation of transmission line, after obtaining the analytical expression of two-dimensional electric potential field distribution in buried-channel CCD devices, it analyzed the effects of key factors of center distance between electrodes, electrode bias voltage, charge storage capacity inside electrode on two-dimensional electric potential field distribution, and defined the two-dimensional electric potential field distribution in buried-channel CCD devices.On the aspect of principle research on achieving charge multiplication in charge multiplication register, it analyzed four points:strong electric field, large charge potential well capacity, overflow controller and DC bias phase. At the same time, according to having Markov nature during charge multiplication or not, the charge multiplication could be sorted as two modes of high-gain mode and ordinary gain mode. Under the different modes, through solutions of Markov-diffusion equation and Malthusian equation, the gain statistical characteristics and gain probability density function were obtained. After building testing system of EMCCD, we found that the size of signal charge packet inside multiplied electrode also could affect the charge multiplication process, besides the bias voltage of multiplied electrode.On the aspect of research on EMCCD imaging model, after the establishment of charge-transfer model and device model of EMCCD, we obtained the system response function and amplitude-frequency response characteristics of EMCCD, and analyzed the effects of charge multiplication process on imaging. According to the experimental testing results, it was obvious that:although the charge multiplication process did not change the distribution of amplitude-frequency response of EMCCD, it increased the detail resolution of EMCCD in low-light condition because the charge multiplication process increased the response amplitude.On the aspect of research on photon counting imaging based on EMCCD, after the establishment of discrete single-photon response model, it obtained the evidences of single-photon detection to estimate the EMCCD. Using the single-photon response model of EMCCD, it discussed the principle of achieving photon incident detection by dual-threshold principle, and gave out the selective evidences of amplitude threshold and frequency threshold. Through the efficiency and error experiments of single-photon detection, it analyzed the property of EMCCD in the mode of photon technology imaging. Through the experiment of photon counting imaging, it proved that:in the mode of photon counting, the minimum responsibility of EMCCD could achieve 0.1 charge/pixel/frame, it obviously preceded the results of the other imaging mode at the same conditions.These works of this paper are a part of research work of Natural Science Foundation project of Jiangsu Province (project NO.BK2008059)-"Research on photon counting imaging mechanism and its key technologies".These works were also supported by grants from Ministry of National Defence of China (project NO.4040508011 and NO. A2620060242).更多还原