大视场长焦平面TDI CCD拼接相机最优成像技术研究

发布时间：2018-08-07 20:44

【摘要】：随着国内外航天光学遥感技术的发展,为了能更快速地、高效地、精确地获取地面目标的图像信息,空间光学相机逐步向宽覆盖和高分辨率的方向发展。近几年,离轴三反光学技术与焦平面多CCD拼接技术已经取得了很大的突破,但是也带来了很多问题,比如结构比较复杂,空间尺寸有限,且电路集成度较高,大功率驱动器件比较密集,长时间工作导致焦平面温度上升很快,降低了图像信噪比和成像均匀性,同时长焦平面的准确安装定位也存在着较大困难,此外,在大姿态角推扫成像条件下如何获取高信噪比、高传函和高匹配图像也存在一定的难度,如果这些问题不解决将严重束缚空间光学相机在宽覆盖和高分辨率方向上的发展。论文以大视场长焦平面TDI CCD拼接相机作为研究对象,主要进行以下几个方面的研究:长焦平面多通道电路串扰噪声的建模与抑制;焦平面温度分析与散热设计;长焦平面高精度安装定位技术;长焦平面全视场内TDI CCD成像参数的最优匹配等。具体研究内容如下:1.详细阐述了多谱段TDI CCD的内部结构、TDI CCD相机的推扫成像原理、长焦平面TDI CCD拼接电路的一致性设计,同时对TDI CCD相机成像质量的两大重要评价指标(信噪比和调制传递函数)进行深入地分析,比较全面地涵盖了TDI CCD相机的设计、开发和研制过程中各环节对静态传递函数的影响,以及在推扫成像过程中环境因素对动态传递函数的影响。2.长焦平面串扰噪声分析与抑制。长焦平面是由多片TDI CCD拼接而成,相互之间存在着串扰噪声,串扰噪声的形态不同、噪声强弱不同,如果分析不正确将很难抑制。本文将结合焦平面多通道TDI CCD电路的结构特点,分析串扰噪声引入机理,对实际遇到的串扰噪声进行特性分析和分类,建立串扰噪声模型并定量分析。着重提出串接限流电阻抑制瞬态驱动电流、暗参考像元提取串扰噪声系数两种串扰噪声抑制方法,通过实验验证,串接限流电阻抑制瞬态驱动电流方法对提高信噪比有显著效果,暗参考像元提取串扰噪声系数方法使响应非均匀性降低到1.8%,和抑制前相比降低了3倍左右,极大地提高了图像质量。3.焦平面温度分析与散热设计。由于焦平面空间尺寸有限,元器件集成度较高、大功率驱动器件布局紧凑,电路长时间工作将会导致焦平面温度上升,最终会影响到相机焦平面成像非均匀性与信噪比。本文将对焦平面电路的热源进行计算,深入分析温度变化对焦平面性能的影响,提出了焦平面结构热传导散热设计,包括元器件分类布局、CCD热沉散热结构设计、基于导热孔阵列和导热铝层的叠层热传导散热设计,通过测试结果对比分析,做散热设计后的水平时序驱动区域电路的温度比设计之前同一区域的温度降低了3℃左右,成像15分钟时响应非均匀性达到2.09%,所有像元信噪比的标准偏差降低到平均信噪比的8%,和散热处理前相比约减小了一倍,验证了散热方式的高效性、稳定性和合理性。4.长焦平面精确安装定位。焦平面是由多片TDI CCD拼接而成,长焦平面安装好后,必须要进行空间位置的校准,为了使长焦平面上所有TDI CCD都处于最佳像面位置,必须要有高精度、可靠的相机焦平面安装定位技术。本文提出一种基于高精度对比传函(CTF)检测的焦平面安装定位方法,分析影响CTF检测精度的因素,提取真实CTF测试值,提高焦平面对比传函的检测精度,通过实验数据分析CTF检测误差均小于1%,说明CTF检测方法的检测精度较高,满足大视场相机焦平面安装定位精度的要求。通过相机调焦功能测试各个调焦位置的CTF值,并拟合出相机的CTF-调焦量变化曲线,求出安装测试点的位置,确定焦平面的安装修调量。最后,对安装好焦平面的相机进行整机CTF测试,相机所有通道的CTF检测值均能达到0.28以上。5.长焦平面成像参数的最优匹配。焦平面多通道拼接后的图像分辨率较高,地面覆盖的幅宽较大,成像期间由于卫星姿态角变化,需要不同的成像模式去获取最佳匹配后的图像。经过推导分析了重要成像参数(积分级数、增益、行频等)对相机动态范围、信噪比和传函(MTF)的影响。深入分析了同速匹配模式和异速匹配模式下MTF的分布情况,在同样条件下积分级数为32级和64级时,同速匹配模式下相机只能在正负侧摆角为10°范围内满足MTF不低于0.9的要求,而异速匹配模式下相机在正负侧摆角为40°的范围内均能满足要求。对比了精调和超精调两种行频匹配方法,分析了各自的行频匹配精度及能达到的MTF,两种方法均使MTF优于0.9。根据相机卫星姿态精度、稳定性和不同姿态推扫成像的MTF分布情况求得最优积分级数和最优增益值,配置完成后实现靶标图像条纹清晰,层次分明。论文对长焦平面TDI CCD拼接相机进行了较为全面的研究,其研究成果适用于大视场、宽覆盖和高分辨率遥感相机应用领域,解决了大视场离轴三反技术和TDI CCD拼接技术带来的长焦平面安装定位不准确、焦平面电路工作不稳定、全视场成像不匹配等技术难题,极大提高了大视场长焦平面TDI CCD相机焦平面电路工作的稳定性、可靠性,提高了图像的信噪比和传函,同时在不同卫星平台姿态任务下实现大视场相机最优图像的获取,具有一定的理论意义和极大的实际工程意义。
[Abstract]:With the development of spaceborne optical remote sensing technology at home and abroad, in order to get the image information of ground targets more quickly, efficiently and accurately, the space optical camera has gradually developed into the direction of wide coverage and high resolution. In recent years, a great breakthrough has been made in the off-axis three reflective technology and the multi CCD splicing technology of the focal plane, but it has also been carried out. There are many problems, such as the complex structure, the limited space size, the high integration of the circuit and the high power drive components. The long time work leads to the rapid rise of the focal plane temperature, which reduces the image signal-to-noise ratio and the imaging uniformity. At the same time, the accurate installation of the long focal plane also has great difficulty, in addition, in the big posture. It is difficult to obtain high signal to noise ratio, high transmission letter and high matching image under the condition of angular push imaging. If these problems do not solve the development of wide coverage and high resolution direction of heavy bound space optical camera, a TDI CCD splicing camera with large field of view long focal plane is used as the research object. Research: Modeling and suppression of crosstalk noise in multi-channel circuit of long focal plane; focal plane temperature analysis and heat dissipation design; high precision installation and positioning technology of long focal plane; optimal matching of TDI CCD imaging parameters in the full field of view of the long focal plane. The specific research contents are as follows: 1. the internal structure of multispectral section TDI CCD, TDI CCD phase is detailed and detailed. The principle of the machine's push and sweep imaging, the consistency design of the TDI CCD splicing circuit of the long focal plane, and the two important evaluation indexes (signal-to-noise ratio and modulation transfer function) of the imaging quality of the TDI CCD camera are deeply analyzed. It completely covers the design of the TDI CCD camera and the shadow of the static transfer function during the development and development of the TDI CCD camera. Effect of environmental factors on the dynamic transfer function in the process of push scanning..2. long focal plane crosstalk noise analysis and suppression. The plane of the long focal plane is made up of multiple TDI CCD. There is a crosstalk noise between each other. The form of crosstalk noise is different, the noise intensity is different. If the analysis is not correct, it will be difficult to suppress the noise. The structure characteristics of the planar multichannel TDI CCD circuit, analyze the mechanism of crosstalk noise, analyze and classify the actual crosstalk noise, establish the crosstalk noise model and analyze the quantitative analysis. Two kinds of crosstalk noise suppression methods are put forward to suppress the transient current of the series connection limit resistance and the noise factor of the dark reference pixel. It is proved by experiments that the method of the series connection limiting current resistance suppression transient driving current has significant effect on improving the signal to noise ratio. The method of extracting the crosstalk noise coefficient by the dark reference pixel reduces the response inhomogeneity to 1.8%, and decreases about 3 times as compared with the pre suppression, which greatly improves the temperature analysis and heat dissipation design of the image quality.3. focal plane. Due to the coke, the focal plane temperature analysis and the heat dissipation design are greatly improved. The dimension of plane space is limited, the integration degree of components is high, the layout of high-power driver is compact, the long time work of the circuit will lead to the rise of the focal plane temperature, which will eventually affect the nonuniformity and signal to noise ratio of the camera focal plane imaging. The heat conduction heat dissipation design of the focal plane structure is put forward, including the classification layout of the components, the design of the heat sink structure of the CCD heat sink, the heat conduction design based on the heat conduction hole array and the heat conduction aluminum layer, and through the comparison and analysis of the test results, the temperature ratio of the horizontal time series drive area circuit after the heat dissipation design is in the same area before the design. The temperature is reduced about 3, and the response to nonuniformity reaches 2.09% at 15 minutes. The standard deviation of all pixel signal to noise ratio is reduced to 8% of the mean signal to noise ratio, and the ratio of the phase ratio before heat dissipation is approximately doubled. It is proved that the efficiency of the heat dissipation, stability and rationality of the.4. long focal plane is precisely located. The focal plane is composed of multiple TDI CCD. In order to make all TDI CCD at the best image position in the long focal plane, there must be a high precision and reliable camera focal plane installation positioning technique. In this paper, a focal plane installation location method based on high precision contrast transfer letter (CTF) detection is proposed, and the analysis of the focal plane installation and positioning method is proposed. The factors that affect the accuracy of CTF detection, extract the true CTF test value, improve the detection precision of the focal plane contrast transmission. The CTF detection error is less than 1% through the experimental data analysis, indicating that the detection precision of the CTF detection method is high and meets the requirement of the focal plane installation positioning accuracy of the large field camera. The CTF value of the camera is fitted with the change curve of the CTF- focus of the camera, the location of the installation test point and the installation and adjustment of the focal plane are determined. Finally, the whole machine CTF test for the camera with a good focal plane is carried out. All the CTF detection values of all the channels of the camera can reach the optimal matching of the imaging parameters of the.5. long focal plane above 0.28. After the splicing, the resolution of the image is high and the width of the ground coverage is larger. During the imaging period, different imaging modes are needed to obtain the best matching images due to the change of the satellite attitude angle. The influence of the important imaging parameters (integral series, gain, traveling frequency, etc.) on the dynamic range of the phase machine, the signal to noise ratio and the transmission letter (MTF) are analyzed. The distribution of MTF under the same speed matching mode and the speed matching mode is analyzed. Under the same condition, when the integral series is 32 and 64, the camera can only meet the requirement of MTF not less than 0.9 within the positive and negative side swing angle in the range of 10 degrees, and the camera can meet the need of the positive and negative side swing angle in the range of 40 degrees under the different speed matching mode. Two kinds of line frequency matching methods are compared with fine and super fine tune, and the matching precision of the line frequency and the MTF that can be reached are analyzed. The two methods all make MTF better than 0.9. to obtain the optimal product classification number and the optimal gain value according to the attitude precision of the camera satellite, the stability and the MTF distribution of the different attitude push imaging, and realize the target after the configuration is completed. The image stripe is clear and the level is distinct. The paper makes a more comprehensive study on the TDI CCD splicing camera of the long focal plane. The research results are applicable to the field of large field of view, wide coverage and high resolution remote sensing camera, and it has solved the inaccurate positioning of the long focal plane installation of the large field off axis triple inverse technology and the TDI CCD splicing technology, and the focal plane electricity. The technical problems such as unstable road work and full field imaging mismatch have greatly improved the stability and reliability of the focus plane circuit of the large field of view long focal plane TDI CCD camera, and improved the signal to noise ratio and transmission of the image. At the same time, it has a certain theoretical meaning to obtain the optimal image of the large view field camera under the attitude of different satellite platforms. Meaning and great practical engineering significance.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP391.41

【相似文献】