测绘相机的温度场设计及MTF测试

针对不同温度场对测绘相机精度影响较大的问题,为了对测绘相机进行合适的温度场的设计及选择,以调制传递函数（MTF）为成像标准,通过光机热集成分析的方式,研究了不同温度场对测绘相机的影响,并找出了适合该相机的温度场。根据此方法进一步寻找出了相机对温度敏感的关键部分,并依此对热设计提供了依据。通过试验测试了该温度场条件下的MTF值,测试结果表明该相机的实验结果与分析值相符合,在56线对/mm处的MTF值高于0.3,满足成像质量要求。     

转镜式高速分幅相机的光学传递函数及分辨率

本文计算了具有矩形或菱形孔径的转镜式分幅相机在离焦情况下的光学传递函数。对二种孔径的计算结果作了分析和比较。并扼要讨论了考虑底片传递函数时的相机分辩率。     

小卫星CCD相机MTF在轨测量与图像复原

基于调制传递函数的基本理论,针对环境与减灾小卫星光学相机,基于刃边法给出了一种在轨测量成像系统调制传递函数的方法.通过选取图像中均匀地物之间灰度变化明显的边缘,对有限采样点进行平滑滤波、曲线拟合和对线扩展函数(LSF)的傅里叶变换获得点扩展函数(PSF),提取调制传递函数(MTF)曲线,进而选取最优的MTF曲线.考虑到采用有约束复原方法时噪声统计、估计的复杂性和欠普适性,本方法通过频率域的去卷积进行复原处理,其优势在于不需要提供传感器、大气状况等参数.并对复原图像从统计特征、清晰度、纹理特征等3方面进行了定量分析和评价.结果表明:复原后的环境与减灾小卫星图像质量得到明显提高,收到良好的复原效果.     

CCD航空相机调制传递函数测试与分析

调制传递函数是衡量CCD相机成像系统性能指标的重要参数.本文在调制传递函数的理论分析基础上,通过对分辨率靶标在相机镜头焦面成像位置与CCD像元之间的偏移,对CCD相机调制传递函数的影响进行分析,建立数学模型,并对CCD相机系统在奈奎斯特频率处的调制传递函数进行了测试,实验结果与计算结果基本吻合.     

光纤传像束同CCD像元耦合的平均调制传递函数分析

通过对光纤传像束同像元不同耦合情况的分析,具体推导了不同耦合情况调制传递函数（MTF）的解析表达式,并进行了对比分析.表明不同的耦合情况,即单根光纤进入邻近CCD像元的不同情况,对MTF的影响不同;单根光纤进入邻近CCD像元的数目越多,MTF值越低.     

信号在电缆中传输失真的补偿

提出了利用电缆调制传递函数(MTF)方法进行频谱补偿。并作了理论分析和求解,是一种较好的信号传输失真的补偿方法。     

用Zernike自由曲面设计弯曲屏幕超薄投影系统

基于非球面离轴反射式投影系统,提出了采用Zernike自由曲面取代非球面进一步优化系统结构的设计方法,并利用Zernike多项式与Seidel像差之间的关系,优化系统的成像性能.设计采用一片Zernike自由曲面取代四片非球面系统中的一片非球面,使投影系统的厚度从24cm减为20cm,边缘视场的调制传递函数（MTF）在50lp/mm时由45％提高到57％,中心视场及0.7视场的MTF由60％提高到了70％,两系统畸变均小于3％,且由于采用柱面弯曲屏幕设计,场曲均在18mm以下.研究结果表明,应用Zernike自由曲面设计投影系统不仅可以提高光学系统的性能,而且可以实现更加超薄的系统结构.     

集成成像技术的像质评价分析

为了研究集成成像非共轭面的成像质量,根据光线追迹原理分析透镜阵列的成像过程,指出三维成像原理并给出不同离焦量下的轴截面成像分辨率;从波动光学角度分析包含离焦波像差的透镜阵列光学传递(OTF),得到集成成像系统的非共轭面调制传递函数(MTF)并指出与单透镜共轭面成像的联系.根据非共轭面分辨率给出符合视觉要求的显示深度计算方法.采用投影仪与菲涅尔透镜搭建显示面积为100×750 mm2的集成成像显示系统,实验结果表明,集成成像轴截面成像分辨率在离焦量增大的情况下迅速下降,非共轭面像质是制约集成成像显示效果的重要因素之一.     

基于波前编码技术红外光学系统无热化研究

波前编码技术是将光学成像与数字图像处理技术相结合,在系统的光瞳处通过添加特殊设计的相位板,对入射光波波前进行重新调制,再经过解码得到清晰的图像,使系统对离焦不敏感,与红外无热化的理念相同。文中比较了原光学系统和采用波前编码系统在不同环境温度下的调制传递函数（MTF）,使用Matlab模拟中间光学部分成像并滤波。结果表明：将波前编码技术应用到红外光学系统当中,可以使系统对由环境温度变化引起的热离焦不敏感,达到无热化的目的。     

线阵推扫式CCD亚像元成像的列向动态调制传递函数

采用亚像元成像技术对焦平面上彼此错开1/2像素的CCD获得的初始图像进行合成,获得分辨率为初始图像2倍的新图像.在CCD采样时间内目标高速运动所引起的像与CCD之间的列向相对位移会导致成像质量的下降.从调制传递函数（MTF）的定义出发,引入像与CCD之间的相对运动速度,推导出了线阵推扫式CCD亚像元成像列向动态MTF的理论公式.对一种CCD的MTF进行具体的数值计算,结果表明亚像元成像技术能够有效地提高线阵推扫式CCD的列向成像质量.     

遥感相机自动调焦的研究

介绍了用差分对比传递函数作为判据进行遥感相机自动调焦的原理，并用黑白条栅和卫星照片作为景物进行了实验研究，实验结果表明：这种方法具有调焦精度高，速度快，受像移影响小，适应性能好的优点。     

In flight MTF monitoring and compensation for CCD camera on CBERS-02

In this article, the approach of simulating ideal tarp scene was proposed to determine the MTF for CCD camera on CBERS-02. The MTF acquired from this technique was compared to those from some common methods. MTFs achieved from different approaches were employed to compensate the CCD images based on three restoration algorithms: the iterative method, the Wiener filter and the modified inverse filter (MIF). The two-dimensional MTF was established with the value at frequency 0.5 for 45° directional MTF as the value at its four corners. This article addressed the variations of the restored CCD images with different techniques of constructing two-dimensional MTF, restoring algorithms and determining the in-flight MTFs. Results showed images restored with the MTF determined from the technique of simulating ideal tarp scene represent the real scene best. And the restoration technique based on the MIF would produce better restored images than the other two techniques. This research also demonstrated that the two-dimensional MTF used for restoration should be interpolated under the control of the MTF for 45° axis, rather than by multiplying the cross-orbit MTF with along-orbit MTF.     

超薄高清手机镜头光学系统设计

现代生活中,手机已经成为了人们生活中必不可少的一部分,照相功能作为手机的基本功能也越来越受到消费者的关注。市场上用户已经把手机性能的选择照相指标作为首位;高像素实用型照相手机已经成为广大消费者竞相首选的对象,因此,设计一款高像素轻薄型手机镜头具有重要的现实意义。围绕焦距是3.5mm手机镜头光学系统进行设计,首先介绍了手机镜头的发展趋势,研究目的、意义以及光学镜头设计的参数要求。介绍了手机镜头的相关知识、同时也研究了作为手机镜头的光学系统初始结构的特点及类型等。设计了焦距是3.5mm手机镜头,系统尺寸紧凑4.149mm;传递函数在中频223lp/mm处MTF≥0.4,在高频446lp/mm处MTF≥0.1,场曲小于0.1mm、畸变小于1%。通过对所设计的手机镜头光学系统的公差分析,结果表明公差合理。     

基于汽车后视系统的短焦距超广角镜头光学设计

充分考虑了鱼眼镜头的特点,设计了一款应用于汽车后视系统的短焦距超广角镜头。系统焦距3.2mm,F数为2.0,全视场角179°,系统总长17.5mm。采用6片式结构,所有镜片均为球面未采用非球面,大大降低了成本,并对各像差曲线进行了分析,全视场MTF值在100lp/mm达到0.5以上,系统结构简单紧凑,像质优良。     

小型CMOS相机系统设计及其硬件实现

采用MT9V032型CMOS数字图像传感器设计了一款完整的小型化、低功耗相机.基于初级像差理论,设计了焦距为12.95mm、F数为5的光学系统.该系统体积小、结构紧凑,在空间频率83线对每毫米处,各视场调制传递函数均优于0.5;电子学系统以现场可编程门阵列作为时序控制平台,控制CMOS输出数字视频信号,数字视频信号通过差分芯片以低压差分信号格式输出到图像采集卡,最后在计算机上成像.实验结果表明,这种相机像质良好、功耗低、移植性强、可靠性高.当时钟为26.6MHz时,帧频为60帧/秒,并可通过调节内部寄存器的值实现多种模式,特别适用于对相机体积以及成像质量要求较高的场合.     

高倍率变焦镜头凸轮曲线的精度分析与整调

本文针对高倍率变焦距镜头凸轮曲线坐标的精度是保证像面位移的重要参数,结合35毫米电影摄影10倍变焦距镜头的生产实践,提出了高倍率变焦距镜头凸轮曲线精度分析和调整方法。     

Image Motion Compensation of Off-Axis TMA Three-Line Array Aerospace Mapping Cameras

To enhance the image motion compensation accuracy of off-axis three-mirror anastigmatic( TMA)three-line array aerospace mapping cameras,a new method of image motion velocity field modeling is proposed in this paper. Firstly,based on the imaging principle of mapping cameras,an analytical expression of image motion velocity of off-axis TMA three-line array aerospace mapping cameras is deduced from different coordinate systems we established and the attitude dynamics principle. Then,the case of a three-line array mapping camera is studied,in which the simulation of the focal plane image motion velocity fields of the forward-view camera,the nadir-view camera and the backward-view camera are carried out,and the optimization schemes for image motion velocity matching and drift angle matching are formulated according the simulation results. Finally,this method is verified with a dynamic imaging experimental system. The results are indicative of that when image motion compensation for nadir-view camera is conducted using the proposed image motion velocity field model,the line pair of target images at Nyquist frequency is clear and distinguishable. Under the constraint that modulation transfer function( MTF) reduces by 5%,when the horizontal frequencies of the forward-view camera and the backward-view camera are adjusted uniformly according to the proposed image motion velocity matching scheme,the time delay integration( TDI) stages reach 6 at most. When the TDI stages are more than 6,the three groups of camera will independently undergo horizontal frequency adjustment. However, when the proposed drift angle matching scheme is adopted for uniform drift angle adjustment,the number of TDI stages will not exceed 81. The experimental results have demonstrated the validity and accuracy of the proposed image motion velocity field model and matching optimization scheme,providing reliable basis for on-orbit image motion compensation of aerospace mapping cameras.     

An Improved Stator Flux Observation Method of Permanent Magnet Synchronous Motor

The stator flux and electromagnetic torque observation is the basis of direct torque controlled permanent magnet synchronous motor (PMSM) drive system. However, the traditional stator flux observer based on voltage model is affected by integral initial values and integral drift, that based on current model is affected by the parameters of PMSM, so a new stator flux observation method is proposed based on an improved second-order generalized integrator (SOGI). Compared to the stator flux observation method based on the conventional SOGI, the proposed method can not only overcome the influence of integral initial values and integral drift, but also completely eliminate the DC offset’s influence. Therefore, the observation accuracy of stator flux is further improved. The simulation and experimental results both show that the proposed method has a higher stator flux and electromagnetic torque observation precision.     

Optimal Nonlinear Distance Toll for Cordon-Based Congestion Pricing Considering Equity Issue

To enhance the image motion compensation accuracy of off-axis three-mirror anastigmatic (TMA) three-line array aerospace mapping cameras, a new method of image motion velocity field modeling is proposed in this paper. Firstly, based on the imaging principle of mapping cameras, an analytical expression of image motion velocity of off-axis TMA three-line array aerospace mapping cameras is deduced from different coordinate systems we established and the attitude dynamics principle. Then, the case of a three-line array mapping camera is studied, in which the simulation of the focal plane image motion velocity fields of the forward-view camera, the nadir-view camera and the backward-view camera are carried out, and the optimization schemes for image motion velocity matching and drift angle matching are formulated according the simulation results. Finally, this method is verified with a dynamic imaging experimental system. The results are indicative of that when image motion compensation for nadir-view camera is conducted using the proposed image motion velocity field model, the line pair of target images at Nyquist frequency is clear and distinguishable. Under the constraint that modulation transfer function (MTF) reduces by 5%, when the horizontal frequencies of the forward-view camera and the backward-view camera are adjusted uniformly according to the proposed image motion velocity matching scheme, the time delay integration (TDI) stages reach 6 at most. When the TDI stages are more than 6, the three groups of camera will independently undergo horizontal frequency adjustment. However, when the proposed drift angle matching scheme is adopted for uniform drift angle adjustment, the number of TDI stages will not exceed 81. The experimental results have demonstrated the validity and accuracy of the proposed image motion velocity field model and matching optimization scheme, providing reliable basis for on-orbit image motion compensation of aerospace mapping cameras.