基于坐标变换的动态光学成像性质研究

利用齐次线性坐标变换，将光学系统的高斯物像共轭理论用齐次坐标变换的方法来描述，并与动态光学理论中的作用矩阵相比较，阐述坐标变换方法与动态光学理论的关系。利用坐标变换方法推导一些重要的动态光学系统的成像性质，验证动态光学的一系列结论。通过本文的研究，证明坐标变换方法与动态光学理论的一致性，也明确在动态光学系统内坐标变换方法的应用。     

基于稳像理论的空间光学遥感像移补偿的分析与计算

动态光学是研究光学系统及元件动态成像特性的一门学科。稳像系统是动态光学系统的重要组成部分。稳像系统是为了维持图像的稳定、清晰,要求光学组元件按规定的要求做相对运动,从而实现图像的最终稳定、清晰。空间遥感成像的分析对于遥感器的运用至关重要。基于稳像理论——动态光学理论,进行了空间遥感器的成像面像移分析,分析结果与采用齐次坐标变换方法所得结论一致,不但证明通过齐次坐标变换方法得出的结果是正确的,而且说明采用动态光学的稳像理论解决以上问题物理概念更清楚,计算简便。同时对于类似的运动光学系统,稳像理论也具有很好的适用性。     

同时实现极坐标变换和径向对数坐标变换的光学方法

本文介绍一种用一维函数坐标变换光学系统,同时实现极坐标变换和径向对数坐标变换的光学方法,给出了实验结果.讨论了在位移、旋转和比例畸变情况下实现不变光学相关的可能方案.     

非共轴光学系统传递函数计算

用坐标变换计算非共轴光学系统是十分有效的。本文讨论了非共轴光学系统传递函数(OTF)的计算要点,并给出了平行光束传递函数的计算方法。计算了一个无焦系统的波动光学传递函数。     

基于等效节点理论确定光轴方法的研究

针对目前高精度光学系统光轴标定存在的误差问题,提出了一种基于等效节点理论对系统实际光轴进行标定的方法,通过建立基准坐标系、节点坐标系和探测器坐标系,结合齐次坐标变换的方法构建适用于实际系统光轴标定的数学模型。以焦距为100 mm,物方节点与像方节点之间的距离为20 mm的光学系统为例,基于小旋量理论对其光轴精度影响因素进行了分析与计算,结果表明平行光管、转台、与标定模型三方面引入的标定误差低于10'。为不同的光学系统基于等效节点理论进行光轴标定时的精度分析提供了方法与依据。     

新型动态多光学目标模拟装置研究

介绍了多光学系统观测平台的检测方法现状，列举了现有检测用光电靶标的局限性。叙述了动态光学靶标的功能原理，提出一种新的检测设备，即双光源动态光电目标模拟装置的设计方案。并对其进行了理论分析和可行性论证。着重对坐标变换过程进行了演算，证明基准转换的正确性。结合理论基础和现有的工程设计经验，论述了该新型双光源动态光电目标模拟装置的工程化设计方案。最后对该设计方案的最终精度进行了分析，验证了该设计方案可以满足多光学系统观测平台的综合检测和标定需求。     

变焦曲线拟合方法的比较与研究

在机械补偿变焦距光学系统中,通过利用变焦曲线控制变倍组与补偿组的移动来达到变焦目的.因此,为使变焦距光学系统在变焦过程中能够始终成像清晰且稳定,拟合出良好的变焦曲线是十分必要的.本文运用动态光学理论、CODE V和ZEMAX宏三种方法分别对一个20倍变焦距光学系统进行变焦曲线拟合,得到相应的运动曲线方程.根据所得到的三组曲线方程,随机选取若干变焦位置点,分别对这些位置点的光学系统离焦量、中心视场MTF和边缘视场MTF进行评价.数据分析表明,动态光学理论拟合出的变焦曲线在满足系统要求前提下更能够保证像面的稳定性.     

大口径光学系统测试用双回转子孔径扫描装置设计与误差分析

设计了一种新颖的双回转子孔径扫描装置,得到了可以覆盖大口径光学系统全口径的子孔径扫描光斑,从而满足了大口径光学系统光谱透射特性的测试需求.结合双回转扫描装置的结构参数误差,基于齐次坐标变换矩阵原理,建立了双回转扫描装置的数学模型,提出了一套分析子孔径扫描精度的方法,并且在设计双回转子孔径扫描装置中实现了应用.分析结果表...     

靶场光学测量中的变焦距光学系统

变焦距光学系统通过调整光学系统参数,改变光学系统的焦距来保证光学系统动态成像的需求。本文从变焦距光学系统的基本原理出发,简单描述了光学补偿与机械补偿变焦光学系统的设计,阐述了常见变焦距光学系统的类型与结构。指出了传统变焦距光学系统存在的问题,结合DSP和步进电机在变焦距光学系统中的最新应用,概述了靶场光测设备的变焦距光学系统的最新动态,分析了电机直传技术在靶场光测设备应用的可行性,意在为新一代数字变焦光学系统提供理论参考。     

靶场光学测量中的变焦距光学系统

变焦距光学系统通过调整光学系统参数,改变光学系统的焦距来保证光学系统动态成像的需求。本文从变焦距光学系统的基本原理出发,简单描述了光学补偿与机械补偿变焦光学系统的设计,阐述了常见变焦距光学系统的类型与结构。指出了传统变焦距光学系统存在的问题,结合DSP和步进电机在变焦距光学系统中的最新应用,概述了靶场光测设备的变焦距光学系统的最新动态,分析了电机直传技术在靶场光测设备应用的可行性,意在为新一代数字变焦光学系统提供理论参考。     

Three-dimensional diffuse optical imaging of hand joints: System description and phantom studies

In this paper we describe a three-dimensional (3D) continuous wave (CW) diffuse optical tomography (DOT) system and present 3D volumetric reconstruction studies using this DOT system with simple phantom models that simulate hand joints. The CCD-based DOT system consists of 64×64 source/detector fiber optic channels, which are arranged in four layers, forming a cylindrical fiber optic/tissue interface. Phantom experiments are used to evaluate system performance with respective to axial spatial resolution, optical contrast and target position for detection of osteoarthritis where cartilage is the primary target region of interest. These phantom studies suggest that we are able to quantitatively resolve a 2 mm thick “cartilage” and qualitatively resolve a 1 mm thick “cartilage” using our 3D reconstruction approach. Our results also show that optical contrast of 3:1–7:1 between the “disease cartilage” and normal cartilage can be quantitatively recovered. Finally, the target position along axial direction on image reconstruction is studied. All the images are obtained using our 3D finite-element-based reconstruction algorithm.     

Linear canonical Wigner distribution and its application

Linear canonical transform (LCT) form a three-parameter family of intergral transforms with wide application in optics. In this paper, we investigate the linear canonical Wigner distribution (LCWD) which is based on the LCT and the classical Wigner distribution (WD). Firstly, the definition of LCWD is discussed. Moreover, the transformation law for the LCWD through a first-order optical system is derived. This new phase-space distribution provides analysis of signals in both space and LCT domains simultaneously. Then, the main properties of LCWD are investigated in detail. Finally, the application of the LCWD is presented. The LCWD is found to be the appropriate phase-space distribution function for light-beam characterization in first-order optical system. Moreover, the moment matrix formalism for beam characterization is studied.     

Generalized wavelet transform based on the convolution operator in the linear canonical transform domain

The wavelet transform (WT) and linear canonical transform (LCT) have been shown to be powerful tool for optics and signal processing. In this paper, firstly, we introduce a novel time-frequency transformation tool coined the generalized wavelet transform (GWT), based on the idea of the LCT and WT. Then, we derive some fundamental results of this transform, including its basis properties, inner product theorem and convolution theorem, inverse formula and admissibility condition. Further, we also discuss the time-fractional-frequency resolution of the GWT. The GWT is capable of representing signals in the time-fractional-frequency plane. Last, some potential applications of the GWT are also presented to show the advantage of the theory. The GWT can circumvent the limitations of the WT and the LCT.     

Reconstruction of band-limited signals from multichannel and periodic nonuniform samples in the linear canonical transform domain

Linear canonical transforms (LCTs) are a family of integral transforms with wide application in optical, acoustical, electromagnetic, and other wave propagation problems. This paper addresses the problem of signal reconstruction from multichannel and periodic nonuniform samples in the LCT domain. Firstly, the multichannel sampling theorem (MST) for band-limited signals with the LCT is proposed based on multichannel system equations, which is the generalization of the well-known sampling theorem for the LCT. We consider the problem of reconstructing the signal from its samples which are acquired using a multichannel sampling scheme. For this purpose, we propose two alternatives. The first scheme is based on the conventional Fourier series and inverse LCT operation. The second is based on the conventional Fourier series and inverse Fourier transform (FT) operation. Moreover, the classical Papoulis MST in FT domain is shown to be special case of the achieved results. Since the periodic nonuniformly sampled signal in the LCT has valuable applications, the reconstruction expression for the periodic nonuniformly sampled signal has been then obtained by using the derived MST and the specific space-shifting property of the LCT. Last, the potential applications of the MST are presented to show the advantage of the theory.     

Linear canonical ambiguity function and linear canonical transform moments

A new phase-space distribution, linear canonical ambiguity function (LCAF), is proposed based on the linear canonical transform (LCT). The properties and physical meaning of the LCAF are given. The LCT moments are introduced and the relationships between the LCAF and the LCT moments are also derived. As an application, simple expressions for the center of gravity of the LCT power spectra and the effective width of the first-order optical system diffracted beam are derived. Compared with the conventional ambiguity function, the LCAF has three additional freedoms, i.e., the parameters characterizing a LCT, which make the LCAF more attractive for the analysis of optical signals.     

Multichannel sampling expansion in the linear canonical transform domain and its application to superresolution

The linear canonical transform (LCT) describes the effect of first-order quadratic phase optical system on a wave field. In this paper, we address the problem of signal reconstruction from multichannel samples in the LCT domain based on a new convolution theorem. Firstly, a new convolution structure is proposed for the LCT, which states that a modified ordinary convolution in the time domain is equivalent to a simple multiplication operation for LCT and Fourier transform (FT). Moreover, it is expressible by a one dimensional integral and easy to implement in the designing of filters. The convolution theorem in FT domain is shown to be a special case of our achieved results. Then, a practical multichannel sampling expansion for band limited signal with the LCT is introduced. This sampling expansion which is constructed by the new convolution structure can reduce the effect of spectral leakage and is easy to implement. Last, the potential application of the multichannel sampling is presented to show the advantage of the theory. Especially, the application of multichannel sampling in the context of the image superresolution is also discussed. The simulation results of superresolution are also presented.     

面向近红外脑功能成像的光学自导引漫射光断层成像方法

为降低近红外脑功能漫射光断层成像(DOT)固有的逆问题病态性,并避免多模态方法的图像配准等问题,提出了基于光学自导引提供先验功能信息的脑功能DOT方法(OT-DOT),并发展了图像重构方法.模拟验证表明:上皮厚度(TLT)已知时,OT-DOT获得的重构量化度(QR)约为传统DOT的4.2倍;当TLT的估计误差小于±10%时,OT-DOT重构的QR值可达92%以上,远远优于传统DOT;噪声鲁棒性测试表明,OT-DOT与传统DOT的噪声鲁棒性相近.利用连续光DOT测量系统的仿体实验重构结果表明,所发展的OT-DOT算法获得的重构结果优于传统DOT算法.     

Multichannel sampling theorem for bandpass signals in the linear canonical transform domain

The linear canonical transform (LCT) describes the effect of first-order quadratic phase optical system on a wave field. The classical multichannel sampling theorem for common bandlimited signals has been extended differently to bandlimited signals associated with LCT. However, a practical issue associated with the reconstruction of the original bandpass signal from multichannel samples in LCT domain still remains unresolved. The purpose of this paper is to introduce a practical multichannel sampling theorem for bandpass signals in LCT domain. The sampling expansion which is constructed by the ordinary convolution in the time domain can reduce the effect of spectral leakage and is easy to implement. The classical multichannel sampling theorem and the well-known sampling theorems for the LCT are shown to be special cases of it. Some potential applications of the multichannel sampling are also presented to show the advantage of the theory.     

The estimation of a unique solution for steady-state diffuse optical tomography by applying mechanical pressure

The accuracy of diffuse optical tomography (DOT) highly depends on two important factors: first, the knowledge of the tissue optical heterogeneities for accurate modeling of light propagation, and second, the uniqueness of reconstructed values of optical properties. Previous studies illustrated that the inverse problem associated with steady-state DOT does not have unique solutions. In this study, we propose a simple method that can be applied to improve this challenging problem of steady-state DOT. In this method, we study the propagation of photons through compressed breast phantoms. The applied mechanical pressure can change the values of optical properties and this pressure dependence of optical properties as a set of constraint equations can be used to improve the inverse problem. The applied pressure can help us to restrict the distribution of possible values of depth and radius of defect inside breast phantom reconstructed by inverse problem.