像增强器MTF测量理想像面选择方法研究

为了能够获得准确的调制传递函数测量结果,对测量系统中投射图像的理想成像面进行选择性调节。通过对微光像增强器调制传递函数测量系统光学成像性质的深入分析,讨论了光学系统的像差特性,利用平均中点取值法实现了微光像增强器调制传递函数测量中对理想成像面的选择。通过与微光像增强器已有测量结果的对比,证明所述方法能够保证微光像增强器调制传递函数测量的准确性。     

一种基于针孔像分析的光学系统调制传递函数测量的自适应背景校正方法

提出了一种基于针孔像分析的光学系统调制传递函数(MTF)测量自适应背景校正的方法。由CCD显微系统采集针孔目标经被测光学系统成像后的针孔像,计算线扩展函数,并对其进行自适应背景校正,获取MTF。该方法与传统方法相比,消除了周围环境光照变化的影响,提高了测量精度。为验证所提方法的有效性,对标准镜头进行MTF测试,将测试结果与理论设计值比对,测试结果差异极大值为0.01;与美国Optikos公司的测试结果比对,测试结果差异极大值为0.015;对大像差光学系统的轴上和轴外进行MTF测试,并将测试结果与美国Optikos公司测试结果比对,测试结果差异极大值为0.013。实验表明,该方法可满足对不同像差光学系统轴上和轴外MTF的测量。     

Integrated evaluation of diffraction image quality in optical lithography using the rigorous diffraction solution for a slot

The method of integrated evaluation of quality of optical diffraction image is proposed. It uses several scalar parameters defined by integral comparison of two functions on the image surface. The first function represents real distribution of electric energy density on this surface, and can be simulated by the solution of corresponding exact or approximate diffraction problem of image formation. The second function describes required energy distribution on the given surface. The method is demonstrated by the example of evaluation of images formed by contactless printing from a mask in optical lithography, where the image function is computed by the known exact solution of plane wave diffraction by a slot in a conducting screen.     

天光背景下混浊大气中成像质量的分析方法

调制传递函数(MTF)定量描述混浊介质对图像质量的影响,它是混浊介质的固有光学特性,利用等效原理可以获得MTF从低频到高频的完整特征.在实际应用中,混浊介质中的图像质量不仅取决于介质的MTF,还与图像的背景辐射密切相关.本文从混浊大气中图像退化机理出发,理论分析了空间频域中天光背景下图像质量的退化过程.参考等效原理,提出了一种考虑天光背景的表观MTF,得到了表观MTF与介质MTF和天光背景的定量关系,从而得到了一种分析背景辐射下混浊介质中图像质量的有效便捷方法.针对图像质量优化方法,从空间频域的角度提出了一种评价原则.     

紫外告警系统探测距离的估算

介绍了紫外告警原理及紫外告警系统的结构组成。基于典型目标(导弹)的紫外辐射特征和紫外辐射的大气传输特性,结合紫外告警系统探测器件的性能参数,根据像平面照度公式,提出了紫外告警系统探测距离的估算方法及模型,实例计算并验证了紫外告警系统在不同观察方位角对固体推进剂导弹的探测距离。分析研究表明,改变CCD最小照度值,像管的增益,光学系统的透过率和相对孔径等探测传感器的性能参数,可以提高紫外告警系统的探测距离。     

Problems of the Grid Size Selection in Differential Box-Counting (DBC) Methods and an Improvement Strategy

The differential box-counting (DBC) method is useful for determining the fractal dimension of grayscale images. It is simple to learn and implement and has been extensively utilized. However, this approach has several problems, such as over- or undercounting the number of boxes due to inappropriate parameter choices, limiting the calculation accuracy. Many studies have been conducted to increase the algorithm’s computational accuracy by improving the calculating parameters of the differential box-counting method. The grid size is a crucial parameter for the DBC method. Generally, there are two typical ways for selecting the grid size in relevant studies: consecutive integer and divisors of image size. However, both methods for grid size selection are problematic. The consecutive integer method cannot partition the image entirely and will result in the undercounting of boxes; the divisors of image size can partition the image completely. However, this method uses fewer grid sizes to compute fractal dimensions and has a relatively huge distance error (DE). To address the shortcomings of the above-mentioned two approaches, this research presents an improved grid size selection strategy. The improved method enhances computational accuracy by computing the discarded image edge areas in the consecutive integer method, allowing the original image information to be used as thoroughly as the divisor strategy. Based on fractional Brownian motion (FBM), Brodatz, and Aerials image sets, the accuracy of the three grid size selection techniques (consecutive integer method, divisors of image size method, and the improved algorithm) to compute the fractal dimension is then compared. The results reveal that, compared to the two prior techniques, the revised algorithm described in this study minimizes the distance error and increases the accuracy of the fractal dimension computation.     

星载均匀像面低畸变广角气溶胶探测仪的研制

为满足空间遥感的迫切需求,设计并研制了一个星载均匀像面低畸变广角气溶胶探测仪样机.该仪器通过利用光阑像差产生的有效像差渐晕提高像面照度的均匀性,解决了广角系统中像面照度不均匀的问题.合理选择结构型式校正了畸变,并且采用全球面光学系统,易于加工和检测.广角气溶胶探测仪的中心波长为670 nm,带宽20 nm,全视场72°,相对孔径1/3.6,焦距20 mm.实验结果表明:研制的星载广角气溶胶探测仪镜头其入瞳大小5.6 mm,边缘视场的相对照度达到95.6%,在36 lp/mm处,轴上视场的调制传递函数值大于0.61,轴外视场的调制传递函数值高于0.58,最大畸变量为-1.95%,完全满足设计指标要求,体积小,适合空间遥感应用.     

红外光电成像系统MTF测试技术分析

调制传递函数是评价红外光电成像系统整机成像质量的重要指标之一。通常MTF的测试方法有狭缝法和刀口法等。详述了倾斜目标靶（斜狭缝和斜刀口）测试MTF的测试原理,并且对该两种方法进行了比对实验。提出一种改进刀口法,将多行数据刃边对齐并排列成一行数据作为刀口扩散函数,能增加采样点数和采样率并提高测试分辨率,进而得到刀口图像,对每行数据先微分得到各行LSF(线扩散函数),再对LSF多行数据构成的新图像按照斜缝法处理过程计算MTF。实验验证表明,该方法数据能够有效地降低在MTF测试过程中的噪声影响,与斜缝法MTF测试结果差值最大不超过7.5%。     

Numerical simulation of the modulation transfer function in planar InGaAs dense arrays

Three-dimensional simulation methodology has been used to evaluate the performance of lattice matched InGaAs/InP double layer planar heterointerface detector arrays. The device characteristics under optical illumination and dark conditions have been computed. The modulation transfer function (MTF) profiles have been calculated with varying device geometries and carrier dynamics. It is found that the p well diffusion radius and minority carrier recombination play important roles in the MTF behaviors of dense arrays. Moderate p well diffusion dimension should be used to balance the device performances between the dark current and MTF profile. Moreover, better MTF characteristic under low light condition can be achieved with higher quality material which has longer recombination lifetime. The influences of underlying mechanisms including photon generated carriers diffusion and carrier recombination processes have been discussed. These simulation methods and results should provide a useful tool for the evaluation and improvement of imaging power of InGaAs focal plane arrays.     

长焦距变焦镜头的温度分析及补偿

为了提高长焦距变焦镜头的温度稳定性,分析了温度对光学系统的影响。在CODE V里对长焦距变焦镜头光学系统进行温度仿真分析,发现温度对光学系统的像质影响很大。采用无热化技术成熟的主动调焦式补偿方式对光学系统的温度效应进行补偿,发现采取补偿后像质有很大改善,但在相机的最大空间频率处的MTF还是较低,且变焦系统各焦距时的最佳像面并不能齐焦。采用机械被动式补偿和主动调焦式补偿混合的方式进行温度补偿,使得变焦系统在要求的全温度范围内有良好的像质,短焦时MTF大于0.5,长焦时的MTF大于0.25,并且焦距也得到补偿,各焦距时的最佳像面齐焦并与CCD的像面位置重合。     

600mm望远镜液晶自适应系统成像光路设计

为了与600 mm望远镜匹配以验证液晶自适应光学的有效性,利用Zemax光学设计软件进行了液晶自适应光学系统的设计和优化.根据望远镜的参量、大气湍流的特性和液晶的特点提出设计要求,然后进行光学系统设计和Zemax软件模拟优化,设计出了满足要求的系统.对该光学系统进行性能评价.设计出的系统与望远镜的组合焦距为35 m, F数为58.求得光学系统在像面处的极限线分辨力为44.8 μm,成像CCD的像元尺寸为16 μm,满足采样定理.液晶自适应光学系统的调制传递函数与衍射极限传递函数非常接近,而且系统的光程差像差在0.1λ左右,说明系统具备优良的光学性能.     

大焦深成像系统的特性研究

如何增大非相干光学成像系统的焦深已成为一项有意义的研究主题，为了增大焦深，通常的做法是缩小相对孔径，但这种做法会降低光学系统的光通量、调制传递函数（MTF）及分辨率，而大焦深成像系统通过在光学系统光路中加入一特殊设计的非球面掩摸板，并用图像处理技术对相位掩模板编码后的图像进行解码得到清晰图像，保证了光学系统在维持原有相对孔径的同时扩大其焦深范围，使光学系统在离焦范围内有好的图像质量，从光学图和系统的MTF两个方面对大焦深成像系统的特性进行了分离，并对结果进行了讨论。     

光强局部选通成像器中光锥耦合技术研究

为了实现景物在强光照射下能够分辨图像的细节,在液晶的光强局部选通成像器中,使用光锥将TFT-LCD液晶耦合到CCD相机上以实现图像的实时传递。通过理论分析和计算,采用光锥耦合获得的耦合效率为14.24%,而透镜耦合则只有1.83%,由前者耦合后构成的局部选通系统,其调制传递函数曲线中奈奎斯特频率为0.518,极限分辨率为34 lp/mm,由此制作的器件,在对高照度下图像的细节分辨,明显高于透镜耦合的器件。分析了造成该系统MTF下降的因素,并提出了进一步改善MTF的技术措施。     

Radiometry of optical systems with quasi-homogeneous sources: A linear systems approach

A convolution is proposed to describe the influence of the source-object distribution and entrance pupil of an optical system on the fall-off of the irradiance from centre of the image plane to its edge.     

应用CCD的投影物镜调制传递函数测量系统

调制传递函数是评价光学成像系统成像质量的重要方法,因而测量光学系统的调制传递函数在各种成像光学系统生产实践中具有相当重要的作用。但是长期以来,投影显示设备的生产中缺少能够定量的检测投影物镜性能的标准化方法。根据线性系统和傅里叶变换的理论,结合液晶投影机投影物镜生产、检测的实际需要,提出了应用CCD图像采集系统的投影物镜调制传递函数测量方法,为生产实践提供了可行的定量判断投影物镜性能的手段。给出了实际物镜的检测结果,并与物镜的设计参量进行了比较,同时对影响系统测量精度的一些因素进行了分析。     

Aerosol lenses propagation model

We propose a model based on the properties of cascading lenses modulation transfer function (MTF) to reproduce the irradiance of a screen illuminated through a dense aerosol cloud. In this model, the aerosol cloud is broken into multiple thin layers considered as individual lenses. The screen irradiance generated by these individual layers is equivalent to the point-spread function (PSF) of each aerosol lens. Taking the Fourier transform of the PSF as a MTF, we cascade the lenses MTF to find the cloud MTF. The screen irradiance is found with the Fourier transform of this MTF. We show the derivation of the model and we compare the results with the Undique Monte Carlo simulator for four aerosols at three optical depths. The model is in agreement with the Monte Carlo for all the cases tested.     

折轴望远系统光学传递函数测试中像分析器的扫描方向

在测量具有潜望高和俯仰观察功能的折轴望远系统的光学传递函数时，往往要求获得任一视场处的子午和弧矢两个方向的ＭＴＦ，那么由正交刀口构成的扫描器必须沿着恰当的方向扫描。本文提出了用旋转像分析器的方法来解决这种复杂系统的ＭＴＦ测试，同时给出了扫描器的转角与望远系统折轴角和视场角的大小关系，以供实际工程设计及测试时参考。     

Vehicle speed measurement based on gray constraint optical flow algorithm

Vehicle speed measurement (VSM) based on video images represents the development direction of speed measurement in the intelligent transportation systems (ITS). This paper presents a novel vehicle speed measurement method, which contains the improved three-frame difference algorithm and the proposed gray constraint optical flow algorithm. By the improved three-frame difference algorithm, the contour of moving vehicles can be detected exactly. Through the proposed gray constraint optical flow algorithm, the vehicle contour's optical flow value, which is the speed (pixels/s) of the vehicle in the image, can be computed accurately. Then, the velocity (km/h) of the vehicles is calculated by the optical flow value of the vehicle's contour and the corresponding ratio of the image pixels to the width of the road. The method can yield a better optical flow field by reducing the influence of changing lighting and shadow. Besides, it can reduce computation obviously, since it only calculates the moving target contour's optical flow value. Experimental comparisons between the method and other VSM methods show that the proposed approach has a satisfactory estimate of vehicle speed.     

基于变形分数傅里叶变换的六重密钥图像加密

提出一种利用变形分数傅里叶变换和双随机相位编码对图像加密的方法.对要加密的图像分别进行两次变形分数傅里叶变换和两次随机相位函数调制,使加密图像的密钥由原来两重增加到六重.利用全息元件,可以用光学系统实现这种加密和解密变换.计算机模拟结果表明,只有当六重密钥都完全正确时,才能准确地重建原图像,这种六重密钥加密方法提高了图像信息的安全保密性.