Bayer滤波型彩色相机调制传递函数测量方法

Bayer滤波型彩色相机广泛应用于航天遥感、空间对地观测、环境监测等领域.由于Bayer滤波片造成彩色相机相比黑白相机在像质方面进一步退化,如何对Bayer滤波型彩色相机成像性能全频段综合评价是目前亟待解决的问题.调制传递函数(MTF)是相机成像性能综合评价的关键指标,传统调制传递函数测量方法无法实现对Bayer滤波型彩色相机MTF全频段高精度测量.为了解决这个问题,本文提出了一种采用旋转刀口靶测量彩色相机调制传递函数的方法.理论方面,推导了Bayer滤波型彩色相机调制传递函数测量理论模型,仿真分析了刃函数采样率和刀口刃边倾斜角度误差对调制传递函数测量精度的影响,并给出了计算算法.实验方面,对彩色相机R,G,B三基色调制传递函数权重因子进行了实验定标,并搭建了基于条纹板和旋转刀口靶的彩色相机调制传递函数测量试验装置.采用旋转刀口靶法和条纹靶板法测量彩色相机MTF结果在耐奎斯特频率f_c处极差为0.061,在空间频率f_c/2处极差为0.043,试验结果验证了所提方法的有效性.     

Moiré fringes as two-dimensional autocorrelation of transmission function of linear gratings and its application for modulation transfer function measurement

In this work, we show that the transmission moiré pattern is two-dimensional autocorrelation of transmission function (2D-ACTF) of two superimposed linear gratings that make a small angle with each other. In this approach, the properties of moiré fringes vs. the relative displacement of the gratings are formulated. By measuring 2D-ACTF of two similar gratings, we evaluate the modulation transfer function (MTF) of the gratings’ generating system. This work is the generalized form of our previous works. The implied MTF measurement method is easier and faster than our previous methods.     

大口径干涉仪系统传递函数校准

 波前功率谱密度(PSD)被用于评价ICF激光驱动器光学元件在中频区域的波前误差。目前主要采用大口径相移干涉仪检测ICF光学元件的波前畸变,通过付立叶变换获得波前的PSD分布。相移干涉仪在较高空间频率分量的测量上存在失真效应,因此需对干涉仪的空间频率传递函数进行校准。本文采用位相比较法测量大口径相移干涉仪的系统传递函数。我们采用衍射光学元件的制造工艺,设计、制作了标准的透射和反射位相元件,比较理论计算值与实测PSD值,分别获得了大口径相移干涉仪透射、反射测量模式的系统传递函数。     

大口径干涉仪系统传递函数校准

波前功率谱密度(PSD)被用于评价ICF激光驱动器光学元件在中频区域的波前误差。目前主要采用大口径相移干涉仪检测ICF光学元件的波前畸变,通过付立叶变换获得波前的PSD分布。相移干涉仪在较高空间频率分量的测量上存在失真效应,因此需对干涉仪的空间频率传递函数进行校准。本文采用位相比较法测量大口径相移干涉仪的系统传递函数。我们采用衍射光学元件的制造工艺,设计、制作了标准的透射和反射位相元件,比较理论计算值与实测PSD值,分别获得了大口径相移干涉仪透射、反射测量模式的系统传递函数。     

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.     

The aberration and the modulation transfer function in LASEK and LASIK: Pupil size dependence

The wave-front aberrations on the postoperative eyes with two different type of excimer laser surgery have been measured by a Hartmann-Shack wave-front sensor. We have calculated the aberrations for both 3 and 6 mm pupils, and with which to acquire the MTF of the eye. There are no significant differences in wave-front aberrations postoperatively (P>0.05) for 3 mm pupil size, but with 6 mm pupil, LASIK-treated eyes exhibit significant higher aberrations than LASEK-treated eyes for 4th and 5th-order aberrations. For individual Zernike terms, there are significant difference in , and . The MTF for 6 mm pupil is much lower than those for 3 mm pupil across all spatial frequencies. The LASEK curve shows higher than that with LASIK at spatial frequencies less than 60 c/d, which means that the optical quality in LASEK-treated eyes showed better than in LASIK-treated eyes.     

Application of moiré technique to the measurement of modulation transfer functions (MTF) of printing systems

It is shown theoretically and verified experimentally that by writing a low spatial frequency Ronchi grating by a computer and printing two copies of it on two transparencies by a printer, the modulation transfer function (MTF) of the printed image can be evaluated by measuring the transmittance of the superimposed gratings in a moiré fringe spacing. Application of the technique is quite simple and the results are reasonably reproducible. The technique does not require a high sensitive intensity detector and a very narrow slit for transmission scanning. Also, the presented technique can be applied to other imaging systems.     

大口径干涉仪系统传递函数的修正和校准

 采用子孔径拼接法对传统系统传递函数校准方法进行修正。将大口径干涉仪视场分成若干个等晕区,采用标准台阶相位比较法分别测得每个等晕区的传递函数,然后将大口径干涉仪系统传递函数修正为每个等晕区传递函数的加权平均,其权重因子由对应等晕区内测试面的功率谱决定。实验结果表明:中心视场对应传递函数和修正后的系统传递函数在3 mm^-1附近处差值大于0.2;修正后的系统传递函数校准方法能更准确地得到波前功率谱密度。     

飞秒电子衍射系统中调制传递函数的理论计算

主要介绍了飞秒电子衍射系统的组成及设计指标. 包括光电阴极、电子聚焦系统、电子偏转系统、双微通道板(MCP)电子探测器等，并给出了基本的设计思路、设计结果. 光电阴极是由位于蓝宝石晶体上面的银膜构成，为了获得足够小的电子束斑以及减小电子上靶时的角度，紧贴栅极后放置一个100μm的小孔，对电子束的形状和大小进行限制. 采用磁电子透镜进行聚焦，电子衍射图样由放置在样品后面的双MCP像增强器进行探测. 在设计计算时，用Monte Carlo方法对光电子的初能量、初角度以及初位置分布进行抽样，用有限元法计算磁透镜 关键词： 飞秒电子枪 有限元法 Monte Carlo模拟 调制传递函数     

傅里叶变换光谱成像仪光谱传递函数研究

根据光学传递函数理论,定义了光谱成像仪的光谱传递函数. 针对基于Michelson干涉仪的时间调制傅里叶变换（FT）光谱成像仪,基于Sagnac干涉仪、Fresnel干涉仪、Lloyd干涉仪的空间调制FT光谱成像仪,推导出相应的光谱调制传递函数和光谱相位传递函数解析表达式,并分析了其物理意义. 光谱传递函数为评价相应光谱成像仪在光谱域的性能提供了一种量化的判据. 与空间域的光学传递函数相结合,成为反映光谱成像仪综合性能的客观依据. 关键词： 傅里叶变换 光谱成像仪 光谱传递函数     

Modulation transfer function of a liquid crystal spatial light modulator

The modulation transfer function (MTF) of a pixelated liquid crystal spatial light modulator (LC-SLM) has been derived as a function of the fill factor. Based on the formula, we have investigated the dependence of the MTF on the orientations and spatial frequency of the input patterns. Furthermore, we have proposed and demonstrated a method for improving the MTF of a LC-SLM.     

基于单数码相机的三维视觉测量数据拼接方法

针对大型物体三维形貌视觉测量,提出了一种新的视觉测量三维数据拼接方法。以一台高分辨率数码相机作为全局测量设备,在测量过程中固定不动,并以数码相机坐标系作为全局坐标系。视觉传感器流动到不同位置对物体各子区域进行测量,获得局部坐标系下的三维数据。以一平面靶标为中介将视觉传感器在各位置的局部坐标系统一到全局坐标系下,从而将三维数据统一到全局坐标系下,完成三维拼接。该方法无需在被测物上贴标记,因此适用于任何材质的被测物,且消除了拼接累积误差。实验结果表明,该方法相对拼接误差为0.076%。以Venus石膏像为被测对象,视觉传感器对其三个局部区域进行测量,给出了局部测量结果及拼接结果。     

光谱辐照度测量的数学模型及其方法研究

光谱辐照度是光谱辐射计量中最基本的参数，是研究各种辐射源及光电探测器特性的重要依据。为提高光谱辐照度的测量精度和量值溯源等问题，国防科工委光学计量一级站采用BB3200K高温黑体作为基准的辐射源，以新型辐射测温法为基础，通过一系列光辐射理论和几何原理推导出辐射温度与辐射光功率之间的关系；通过对光辐射功率的绝对测量，并结合低温辐射计，从而完成了光谱辐照度量值的精度测量。该理论奠基了以探测器为基础的新的光辐射量传体系。主要介绍了在光谱辐照度标准装置的项目中复现光谱辐照度所建立的数学模型及新的测试方法，给出了测量结果，并简要介绍了基于该理论的测量装置的组成及原理。     

Solving the atmospheric scattering optical transfer function using the multi-coupled single scattering method

The atmospheric scattering optical transfer function （OTF） is solved by applying the multi-coupled single scattering （MCSS） method to the three-dimensional radiative transfer equation （RTE） under the periodic ground condition. This approach is a direct hit to the atmospheric scattering OTF using the same original context of modulation transfer function （MTF） measurement, i.e., images of sinusoidal grating at different spatial frequencies. Both the amplitude and phase shift of the OTF at various zenith and azimuth angles can be obtained at an arbitrary spatial frequency.     

紫外光学传递函数测量装置研究

光学传递函数是评价光学系统成像质量的重要指标,针对目前光学传递函数测量只能覆盖可见光和红外波段,自行研制了紫外波段(260 nm～400 nm)光学传递函数（OTF）测量装置。介绍了装置的原理及组成,采用中心波长为0=300 nm和0=380 nm 2种OTF标准镜头在2个光谱范围内对OTF测量装置进行了标定和测试,结果表明:调制传递函数（MTF）的测量值与理论值的偏差:0.03（轴上）;0.05（轴外）。最后,对装置的测量不确定度进行了评估。     

光栅图像传输法测量海水光学传递函数

根据成像系统光学传递函数的相乘率,用刻有不同空间频率光栅的目标板,研究了在有水体和无水体情况下,光栅图像的传输情况。然后运用mathcad2001软件对采集到的光栅图像进行分析和计算,获得海水的光学传递函数。通过人为地改变水体长度、水中悬浮物质浓度和水体含盐量等,定性地研究了影响海水光学传递函数的因素。该测量方法在激光水下成像、水下目标探测以及对潜激光通信都将具有重要的推广应用价值。     

利用Michlshon干涉仪测量CCD的调制传递函数

介绍了利用Michlshon干涉仪测量CCD调制传递函数的方法,与其他方法相比,该方法具有测量装置简单、将正弦图样投射到待测CCD阵列上无需借助光学系统等特点。给出了典型的线阵和面阵CCD的调制传递函数曲线的测量结果。     

非理想情况下的CCD调制传递函数的综合表示方法

从理论上讨论了沟道类型对CCD调制传递函数的影响,并在前期工作的基础上给出了非理想情况下的CCD调制传递函数的综合表示方法。利用数值模拟的方法对非理想情况下的CCD调制传递函数与理想情况下的CCD调制传递函数进行了比较。     

On the use of the digital image correlation method for heterogeneous deformation measurement of porous solids

In this paper, several crucial issues arising from the application of the digital image correlation (DIC) method to the measurement of heterogeneous deformation of porous solids are discussed. To handle samples with complex geometry, the performance of the two commonly employed DIC methods, namely the subset-based DIC and the finite-element based DIC methods are first evaluated and compared. A combined DIC approach and an adaptive DIC approach suitable for samples with discontinuities/holes are then proposed. Aluminum plates with circular holes subject to compressive loading are employed to evaluate the accuracy of the proposed methods. It has been found that in addition to other factors such as the number of pixels and speckle size, the orientation of the camera lens also plays an important role on the measurement accuracy. A calibration method for the adjustment of camera orientation is proposed, which leads to a good agreement between the experimentally measured displacements and finite element simulation results. Another finding of the presented work is that for relatively stiff specimens, the deformation of the loading system itself must be considered in order to obtain an accurate displacement.     

小尺度阻尼边界封闭空间声传递函数的有限元素法计算

如何求解阻尼边界封闭空间中声源点到接收点的低频声传递函数已成为目前小尺度封闭空间可听化技术研究的关键技术，能处理任意形状及复杂边界条件的有限元素法可作为求解该问题的适合方法，以室内声声有源Helmholtz方程及其相应边界方程为基础，本文推导出了用于小尺度阻尼边界封闭空间声传递函数的有限元素求解方法，并编制了相应的计算机程序，在算例中，首先通过与模态叠加法计算结果进行比较，验证了该方法的正确性。最后计算了某型车体内腔中任意两点间声传递函数。