【作者】 卢振华；

【导师】 郭永飞；

【作者基本信息】 中国科学院研究生院（长春光学精密机械与物理研究所） ， 机械电子工程， 2012， 博士

【摘要】 调焦技术是空间光学遥感相机（以下简称遥感相机）研制过程中的关键技术之一。调焦系统作为遥感相机的重要组件，是保证成像质量的关键部分。基于数字图像的自动调焦方法，结构简单，智能程度高，在普通数码相机中已经得到了较多的应用。基于图像的自动调焦关键是要建立图像质量评价函数(检焦函数)。图像质量评价函数值是指导自动调焦过程的依据。目前普通数码相机中常用的图像质量评价函数大多都依赖相机对同一个景物多次成像。而推扫式遥感相机的特殊性在于从同一片CCD中不可能获得基于同一景物的多次图像，因此普通的检焦函数不能直接应用于推扫式遥感相机。为解决这一问题实现推扫式遥感相机基于图像的自动调焦，本文提出了一种不依赖于相机对同一景物重复成像的绝对式检焦算法，并根据绝对式检焦算法实现了推扫式遥感相机基于图像的自动调焦；同时文中在研究了推扫式遥感相机成像过程的基础上，从另一方面提出了在推扫式遥感相机中得到基于同一景物的重复图像，利用常用检焦算法完成检焦过程的方法，并通过提出相适应的聚焦方法同样实现了推扫式遥感相机基于图像的自动调焦。最终通过建立相应的实验平台对文中的调焦方法做了测试验证。根据以上方法本文具体的研究有如下几点：1、在信噪比一定时，MTF体现成像系统对各频率的传递能力，从频域角度全面地反应了系统的成像质量。用图像处理方法反演计算MTF时，并不依赖于对某个景物的成像。本文提出的利用在时域中和MTF对应的线扩散函数(LSF)作为检焦函数，不依赖相机对某一景物多次成像，属于绝对式检焦函数。并且基于LSF的检焦过程避免了傅立叶变换，保证了较高的检焦实时性。同时文中研究实现了从遥感图像中提取LSF的方法，最终通过曲线拟合将LSF的分辨率提高到了0.1倍像元尺寸，保证了较高的检焦准确性。2、随着遥感相机成像覆盖范围的不断扩大。现有CCD器件的尺寸已经远远不能满足大焦面遥感相机的要求，必需要用拼接技术利用多片CCD来满足成像要求。根据推扫式遥感相机的成像过程，在CCD的拼接结构中保留一定的重叠成像区域，则利用这些重叠区域可以从不同的CCD中获得基于同一景物的重复图像。本文正是从这一角度出发提出了将现有的图像检焦函数应用于推扫式遥感相机的方法，为推扫式遥感相机的自动调焦提供了可行性依据。3、在分析了现有的聚焦方法的基础之上，针对本文提出的推扫式遥感相机基于图像的检焦方法，研究提出了与检焦方法相适应的聚焦策略。4、针对本文采用的自动调焦方法，依托遥感相机的研制，建立了调焦验证实验板，并提出了相应的软件实现方案，实现并测试了调焦过程。根据测试验证结果，对算法的精度及实时性做了详细的分析。结果表明本文提出的推扫式遥感相机图像自动调焦方法具有较高的可行性，为实际的应用提供了解决方案。更多还原

【Abstract】 Focusing technology is one of the key technologies in the development ofspace optical remote sensing camera (referred hereinafter as a remote sensingcamera). As an important component of remote sensing camera, focusing system is akey part to ensure the imaging quality. Automatic focusing method based on digitalimages with simple structure high degree of intelligence has got more and moreapplications in a common digital camera. The key of auto-focusing based on imageprocessing is to establish the image quality assessment function (focus-checkingfunction). Under the guidance of real-time calculation with image quality evaluationfunction, the focusing action can be implemented correctly. Currently the imagequality evaluation function used in ordinary digital camera mostly relies on thecamera imaging the same scene several times. The specific imaging way of thepushbroom remote sensing camera leads to the result that images of a same scenecan not be obtained several times from one CCD. Therefore, the ordinaryfocus-checking function can not be directly applied to the pushbroom remotesensing camera. To solve this problem, this paper proposed one absolutefocus-checking function independant on repeatedly imaging of the same scene, andrealized the auto-focus by image in pushbroom remote sensing camera. On the otherside, after the research on pushbroom imaging principle, a method to get therepeated images of the same scene in the pushbroom remote sensing camera wasproposed, and the traditional focus-checking method was used. With corrected focusing method proposed the auto-focus by image in pushbroom remote sensingcamera was also realized. At last the experiment plate was set up, and the methodproposed in this paper was tested correspondedly. According to the above methodsthe specific study in this paper are as follow:1) With certain SNR, the MTF embodies the imaging system’s transmissioncapacity of different frequencies, also reflects the imaging quality of the systemfrom the frequency domain. The inverse calculation of MTF from image does notdepend on the imaging of certain scene. The absolute focus-checking functionproposed in this paper, using the line spread function (LSF) witch is thecorrespondence of MTF in time domain, does not depend on the camera imagingone scene repeatedly. The focus-checking process based on LSF avoided the Fouriertransform, ensuring a high level of real-time in focus-checking process. This paperalso studied the method of picking up LSF from remote sensing images. Then withthe curve fitting the resolution of LSF is increased to0.1times the pixel size, whichensured a high accuracy.2) With the expanding coverage of remote sensing camera image, the size ofthe existing CCD device has been far from satisfying the requirements of remotesensing camera of large focal plane. The stitching technique of using multi-chipCCD is necessary to meet the image requirements. According to the pushbroomremote sensing camera imaging process, retaining a certain overlapping imagingarea in the splicing structure of the CCD, duplicate images based on the same scenefrom different CCDs can be got from these overlapping regions. From thisperspective, this paper proposed the method using the existing image focus-checkingfunction into the pushbroom remote sensing camera,which provides a strongfeasibility for the pushbroom remote sensing camera auto-focus.3) After analyzing the existing focus-methods, according to the focus-checkingmethod based on image proposed in this paper, the correct focus-method was set up.4) Aimed at the Auto-focusing method proposed in this paper, a validation andtesting board was built with corresponding software to implement the auto-focus.According to the results of the test, a detailed analysis of the accuracy and real-time was conducted. The results showed that the auto-focusing method proposed in thispaper for pushbroom remote sensing camera using image has a high feasibility, andprovids a solution for practical application.更多还原