摘要EMCCD能够在微光条件下，获得高质量的图像。论文详细分析和讨论了自动增益控制算法的原理，对各个曝光参数对EMCCD成像质量的影响做了实验比较。最后本文提出一种基于“固定灰度级”的自动增益控制算法，并验证算法的可行性，实验证明，此算法能够达到预期的效果。9380
自动增益是自动拍照的摄像系统中的必不可少的功能组成部分。对于一个成像系统而言，图像亮度由场景光强、光圈大小、曝光时间、增益等四个因素所决定。在自然情况下，场景光强由自然光的光强所决定，不能方便地自动控制。因此，为了能自动获得亮度适中、细节表现清晰的图像，只需要对光圈大小、曝光时间、信号增益这三个量进行有效控制便可以实现。在本系统中，光圈大小属于手动控制，曝光时间一定,因此只需要对信号增益进行自动控制便可。
自动曝光就是成像系统对所拍照物体进行自动曝光，以获得亮度适中的图像。一般包括光强测量、场景分析和曝光补偿等三个步骤，可以用光学和电子学两种方式来实现。自动增益就是根据当前图像亮度情况自动调整放大器的增益以调整图像的亮度。
关键词 : EMCCD, 图像亮度,自动曝光,自动增益
ABSTRACT
In low-light-level conditions, EMCCD could get high-quality images. This thesis analyzed and studied the theory of the AG control arithmetic, and did a comparison about the effect of the various parameters on the quality of EMCCD imaging. Then, the thesis explored an AG control arithmetic based on “a fixed gray level” and verified the feasibility of the arithmetic. The experiment Proved that this arithmetic could achieve the desired effects.
And the auto-exposure and auto-gain are essential components of functions of camera system. For an imaging system，the light intensity of the scene，aperture size，exposure time and signal gain determine the brightness of the image. In nature，the natural light intensity determines the light intensity of the scene: one cannot easily control it. Therefore ,in order to automatically obtain moderate-brightness images，it is only needed that the aperture size, exposure time and signal gain are effectively controlled.In this system，theapertuxesize15manuallyeontrolled，and exposure time and signal gain are automatically controlled.
The Purpose of auto-exposure is to obtain moderate-brightness images by imaging system automatically exposing to the objectives . Generally it includes three steps :light intensity measurement，scenario analysis and exposure compensation . And auto- exposure has optics- implemented way and electronic- implemented way .The purpose of auto-gain is to adjust the image brightness by automatically adjusting the gain of amplifiers based on the image brightness.
Keywords: EMCCD; Image Brightness ; Auto-exposure : Auto-gain ;
目 次
1. 绪论 1
1.1课题背景 1
1.2 EMCCD的发展概况 1
1.3 论文结构介绍 2
2. 成像系统图像亮度的决定因素 3
2.1.场景光强 3
2.2.光圈大小 4
2.3．曝光时间. 4
2.4．信号增益 4
3. EMCCD系统结构与工作原理 5
3.1 EMCCD 的结构 5
3.2 EMCCD的工作过程 9
3.3 EMCCD的成像系统原理[19] 9
第四章 微光图像基本特征分析 10
4.1微光图像特征 10
4.2 微光图像直方图统计分析 11
第五章 EMCCD自动增益控制 14
5.1 自动增益算法研究[23] 14
5.2曝光参数对EMCCD成像质量的影响 17 EMCCD的自动增益与算法实现:http://www.youerw.com/tongxin/lunwen_8092.html