中国科学院遥感与数字地球研究所-高光谱遥感应用技术研究室

【作者】             刘学                                                                                                                                             

【导师】             童庆禧；张兵；郑兰芬

【 学位年度 】    2008

【论文级别】      博士    

【关键词】          航空遥感，多模态航空数字相机，几何成像，快门延迟，不同步曝光，机载稳定平台，像移补偿 

【Key words】   Aerial Remote Sensing, Multi-mode Airborne Digital Camera System, Geometric Imagery, Shutter delay, Unsynchronized Exposure, Airborne Stability Platform, Image Smear Compensation 

【中文摘要】 

“十五”期间，在国家“863”计划和中科院创新项目的支持下，中国科学院遥感应用研究所和上海技术物理所于2006年联合研制成功了多模态航空数字相机系统（Multi-mode Airborne Digital Camera System, MADC）。MADC系统在无人机、直升飞机、中低空以及高空飞机等多种平台上进行了二十余架次的航空数字成像飞行实验，获取了大量高分辨率、高质量的图像数据。鉴于航空飞行平台的不稳定性以及MADC系统设计结构方面的考虑，CCD数字相机的高精度几何成像研究始终是该系统发展的一个重要技术环节。

        本文从提高MADC系统成像几何精度的角度出发，重点从以下几个方面进行了研究和论述：

1. 分析了在我国发展航空遥感和航空数字相机系统的重要意义；研究和总结了国内外多种成熟航空相机系统的构建模式和几何成像原理；介绍了MADC系统的系统组成、工作原理和试验情况；提出并分析了对MADC系统几何精度影响最大的四个关键因素。

2. 总结并分析了机械加工精度降低和加工误差产生的主要原因、常用解决方法和数控技术对提高加工精度的重要意义。分析了MADC系统旧型安装基座对成像精度的影响；为MADC系统研制了新型安装基座，使系统的加工精度和安装精度提高到能与光学组件的精度相匹配。

3. 对相机机械快门的结构特点、快门延迟和不同步曝光的原理及对系统整体几何成像精度的影响进行了分析。详细介绍了为MADC系统专门研制的快门控制系统的原理和性能。设计了简便可行的实验室测试方案和测试控制程序来对MADC系统各单台相机的快门延迟和多台相机的曝光不同步时间进行测量，基于该实验室测试方案提出了两者的计算方法。经过多次实验室测试实验，确定了MADC系统相机的快门延迟时间在几十毫秒的量级，多台相机的不同步曝光时间在几毫秒的量级。

4. 详细分析和评价了振动对航空相机成像几何精度和质量的影响。研究和总结了国内外机载稳定平台的研究现状。在深入学习和分析航空稳定平台的原理、结构和功能的基础上，提出了MADC系统专用机载稳定平台的设计方案；该方案的设计思路和技术指标经过详细计算和论证后确定是可行的，正付诸于加工制作阶段。

5. 分析了像移特别是前向像移对航空相机成像质量的影响，研究和学习了几种常用的像移补偿实现方案。针对MADC系统的系统组件和硬件构成情况，设计了专用的外置机械式像移补偿模块，使之能够推动系统整体动作来实现对飞机运动引起的前向像移的补偿，提高MADC系统的几何成像精度。

        通过对以上几个影响MADC系统几何成像精度的关键技术进行的重点研究和分析，有利于对系统软硬件做进一步的优化集成，可以大大提高MADC系统的几何成像精度，获取更高质量的航空影像。本文的研究十分有利于将MADC系统发展成为一套具有我国自主知识产权的成熟的航空数字摄影系统。

【Abstract】

 Multi-mode Airborne Digital Camera System (MADC) was developed by Institute of Remote Sensing Applications and Shanghai Institute of Technical Physics in 2006, under the support by State 863 Projects and Innovation Projects of Chinese Academy of Sciences. MADC system has already obtained many high-resolution and good quality images through more than 20 times aerial photography experiments on different flight platforms, such as unmanned aerial vehicle, helicopter and fixed-wing aircraft. Considering  the instability of flight platforms and the special structuredesign of MADC system, we always hold that the high-accurate geometric imagery is an important technique for CCD digital cameras.

      In order to improve the geometric accuracy of imaging by MADC system,  some important problems are deeply studied in this paper:

1. The significance of developing aerial remote sensing and airborne digital camera system in China was Analyzed; the constructive mode and the principle of geometric imagery according to some airborne digital camera systems at present was researched and summarized; the composition, working principle and aviation experiment of MADC system were introduced; the four key factors which mostly affecting the geometric imagery accuracy of the MADC system were proposed and analyzed.

2. The main cause of the machining precisionreducing and the machining error producing and its common solution method were summarized,  the significance of improving machining precisionusing the numerical control technology was analyzed. After the Analyzing of  the effect of geometric imagery useing the old type installing base, a new type installing base for MADC system was researched and produced, which can match the machining and installing precisionto the optical devicein a higher level.

3. The effect on the geometric imagery precision which caused by mechanical shutter structure, shutter delay and unsynchronizedexposure were studied. After the introduction of the principle and function of shutter-control system for MADC system, a simple and feasible testing plan in laboratory for measuring the accuracy time of shutter delay and unsynchronizedexposure was proposed. the calculation methodabout this two values was put forwand based on the testing plan. The camera shutter delay and the unsynchronizedexposure of MADC system were determined through the test. The camera shutter delay is up to several tens milliseconds and the unsynchronizedup to millisecond.

4. Vibration has important effect on both the geometric imagery precision and the image quality.The art of the researching of airborne stability platform was sand studied. Based on the deep understanding and nanlyzing of the principle of the aerial stability platform, a feasiable special design of the platform were put forword. The feasibility is supported by detailed calculation and the design is under-making.

5.After the analyzeing of  the effect on imaging quality of aerial camerawhich caused by image smear especially the forward image smear, some common methods for image smear compensation were studied. According to the special structure of MADC system, the external image smear compensation module was desighed which can push the whole camera system moving to compensate the image smear and improve the geometric imagery accuracy.

      After emphatically analyzing and researching for the key technologieswhich affect the geometric imagery accuracy of MADC system, the hardware and the software of MADC system should be integrated with optimization. The geometric imagery accuracy of MADC system should be greatly improved, which could help us obtainning more high-quality aerial images. This paper can accelerate the improving of the MADC system  and get the system  become a developed aerial digital photogrammetry system with independent intellectual property of our country.