光学系统实现热补偿的通用条件

运用光学系统的近轴成像公式，推导出微分形式的物面位于任意位置时热补偿的通用条件，包括薄单透镜、密接薄透镜组和分离薄透镜组等不同情况。推导过程中假设物面位置不随温度发生变化，并且忽略分离薄透镜组中各组分上光线入射高度随温度的变化。利用推导的条件建立了像距的归一化温度变化率与各透镜光热膨胀系数之间的关系，指出所得到的条件具有更加普遍的意义，能够指导机械和伺服控制系统的工程设计，并且在物面位于无穷远时与目前普遍采用的热补偿条件相吻合，即光学系统的光热膨胀系数等于壳体的热膨胀系数。     

紫外像增强器分辨力校准装置与方法研究

紫外像增强器作为导弹紫外告警系统、紫外预警系统以及各类紫外辐射监测系统的核心部件，其参数准确与否，直接影响到系统的图像质量。为保证测试数据的准确性，研制紫外像增强器分辨力校准装置，校准装置所用紫外光源是波长范围为200 nm～400 nm的紫外光，相对应的分辨力靶、滤光处、光学成像系统均要求能够透射紫外光，由于紫外波长较短，容易引起散射效应而产生大量的杂散光，设计的分辨力靶采用紫外级石英，紫外光学成像系统采用透射式结构，选用同轴共轭透镜作为紫外光学成像系统。实验和测量不确定度分析验证校准装置的测量不确定度为5%。     

Determination of the resolving power of optical systems in the formation of speckle images

Relations for the calculation of the limiting resolvable spatial frequency of a speckle image of a line mira used as a test object in the determination of the optical power of optical systems are presented. The influence of the speckle structure on the extraction of information about the shape of the object observed from the image recorded is taken into account by using the equivalent modulation transfer characteristic of the optical system than determines the transfer of spatial frequencies of the envelope of the speckle image and the threshold characteristic of speckle noise conditioned by fluctuations of the amplitudes of individual speckles. Conditions, in which the prevailing influence on the quality of the image recorded is exerted by the speckle structure, atmospheric phase distortions, and discretization noise, are determined.     

多角度耦合分幅相机光学系统设计

为实现高速相机的分幅功能,本文提出一种采用多角度耦合分幅方式的高速相机光学系统。该系统分幅结构采用多组相同的光学系统,在平行于物面的圆周上均匀分布,分别从不同角度拍摄同一物面,在保证各组系统的物方视场相同的情况下,每组光学系统的光轴与物平面的夹角均相同,通过优化设计得到全视场的最佳成像。根据需求,使用光学设计软件设计了多角度耦合四分幅成像中长焦光学系统并绘制三维立体仿真模型,分析了每组像面像质、照度以及畸变等相关参数,调制传递函数MTF在频率为50 lp/mm处不低于0.5,F数为2,畸变小于0.4%,相较于常用的棱镜和反射棱锥分光方式,无需额外分光结构,像面照度提高4倍以上。结果表明成像质量理想,分幅相机系统各像面所成像一致性高。     

Geometrical optics analysis for reduction of trapezoidal image distortion in a single prism-based optical fingerprint scanner

A single prism-based optical fingerprint scanner structure is mathematically analyzed by using geometrical optics approach. Important parameters including a tilting angle of the fingerprint accepting plane, a geometrical-optic distant difference, a trapezoidal image distortion, an object compression ratio, and an orientation of a two-dimensional image sensor are formulated for the first time in terms of all three angles of the prism and the prism material. In addition, based on our mathematical model, we propose to design all three angles of the prism in such a way that the plane accepting the fingertip observed from one side of the prism is normal to the optical axis of the system. In this way, the imaging plane is perpendicular to the optical axis, eliminating the trapezoidal image distortion and leading to ease of implementation. Experimental verification using three commercially available dispersion prisms made from three different glass materials and one prism based on our design concept shows that a prism with higher refractive index provides lower trapezoidal image distortion. The experimental data generally obeys our theoretical analysis.     

Reconstruction of an acoustical image using an ‘acousto-electronic’ lens device

Present acoustic imaging apparatuses give only a virtual image of the insonified object. Several studies have been conducted in order to pick up the information from such an image, such as holography and computer data processing. These techniques are very involved, and so simpler processing systems have been analysed in our laboratory in order to reconstruct a true image. Our first system used optical processing of the acoustic echo. In this paper, a second, acousto-electronic, system is described, which enables like the first the attainment of very high image rates in the B-scan mode.     

Imaging through a scattering medium with an interferential spectrometer by selection of an amplitude modulation correlator

Low-coherence interferometric systems provide three-dimensional imaging through scattering media by measurement of the object's temporal response. An optical correlator is presented that allows direct recording of the signal issued from the object under reflection. The filtering technique enhances the image visibility and allows one to obtain an image with a good signal-to-noise ratio. The performance of two particular imaging systems, point-to-point and vertical-slice imaging, is discussed with an object comprising two cover plates that are attached.     

Exact analytical theory of aberrations of centered optical systems

In the paper we present a new theory designed to overcome the deficiencies of the existing aberration theories. The main advantage is the theory’s capacity to perform analytical, direct, and accurate radius, and thickness calculations of aberration corrections for optical components and systems. Methodologically, we derive exact formulas for bilinear transformations from an object to an image space. Next, we introduce relative parameters in the matrix coefficients and by combining bilinear and matrix transformations we develop exact corrections on-axis aberrations and field aberrations such as distortion, astigmatism, and curvatures (including sagittal and tangential). The theory with an accuracy of 10^?8 mm (except for tangential and sagittal coma) allows precise radius and thickness calculation of components and systems for aberration corrections, sets exact coordinates of free-form surfaces, and enables the study of the surface and component capacities for aberration correction. The theory has supported the design of more than 10 different patented optical systems.     

Computer design of electrostatic systems of charge particle optics: Systems with spherical electrodes and a fine-structure grid

Problems in computer-aided design of 3D optical systems for charged particle optics are analyzed. The results of simulation of electron-optical systems of optoelectronic transducers with two cathode packs (spherical cathode-plane fine-structure grid as the accelerating electrode and plane cathode-spherical fine-structure grid) are considered. We note a low technological efficiency of such structures and unsatisfactory quality (as it regards some parameters) of the image being recorded due to spherical electrodes and a fine-structure grid in the cathode pack. Numerical analysis of the effect of adjustment of the design on the quality of the image being recorded is carried out.     

Radial stereo imaging system for three-dimensional reconstruction

In this paper, we propose a radial stereo imaging system for three-dimensional reconstruction of an object. This system uses a novel optical device which consists of a camera and two reflected mirrors. It can reconstruct three-dimensional model of an object by capturing one image. Depending on the reflection of the mirrors, each world point in the scene has a pair of points which sit in the inner and outer of the captured image, respectively. We firstly analyze the imaging constraint of the proposed system, and then derive the geometrical relationship between world point and image point pair to calculate the three-dimensional coordinate values of an arbitrary point on the object, which means that the three-dimensional model of the object can be recovered. Experiments are carried out to prove our design, and the results show that our radial stereo imaging system is convenient and effective for the three-dimensional reconstruction of an object. This system can be used in variety of applications, such as virtual reality and commodity show.     

Digital holographic tomography based on spectral interferometry

A digital holographic tomography system has been developed with the use of an inexpensive broadband light source and a fiber-based spectral interferometer. Multiple synthesized holograms (or object wave fields) of different wavelengths are obtained by transversely scanning a probe beam. The acquisition speed is improved compared with conventional wavelength-scanning digital holographic systems. The optical field of a volume around the object location is calculated by numerical diffraction from each synthesized hologram, and all such field volumes are numerically superposed to create the three-dimensional tomographic image. Experiments were performed to demonstrate the idea.     

采用凝视器件的搜索跟踪系统中的扫描补偿光学技术

为了充分发挥器件的性能,采用凝视探测器件的搜索跟踪系统需要特殊的光学结构补偿搜索跟踪时产生的扫描效应。给出了物方和像方扫描补偿光路的形式和构成,分析了平行和会聚光路两种不同补偿结构的特点,论述了扫描补偿引入的光学问题以及相应解决途径,提出了扫描补偿引入的最大光学原理性误差小于1/3~1/4像素的观点。     

Lensless imaging of an arbitrary object

A new class of imaging systems that do not require the use of lenses or similar optical devices is introduced and theoretically investigated. In particular, it is demonstrated that, if an arbitrary plane object is illuminated by an appropriate spherical wave front (generated from a monochromatic point source), then a magnified image of the object intensity distribution can be observed in any transversal plane along the light-propagation direction within the far-field (Fraunhofer) diffraction region. The phenomenon is based on the fact that, under certain conditions, the spherical wave front can modify the energy's angular spectrum of the field distribution in the object plane such that this spectrum replicates the spatial intensity distribution of the object.     

Computer modeling of optical shadow-casting processor

Computing employing optical signal presupposes information being encoded optically. Many digital optical computing system employs pixel patterns to represent different logic level. Cellular logic, symbolic substitution, morphological and image processing could be performed on such pattern-coded information. Such systems have generally been analyzed by geometric optics. In this work, we propose to model such computing systems using laws of electromagnetic propagation. Results predicted by both geometric optics and the computer model are provided for a pattern-coded full adder/subtracter implementation. The model is general enough to be extended to other systems with more complicated coding pattern and could serve as design tool for optimizing a computing system using pattern-coded logic.     

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。     

Design of Double Cassegrain reflective mirrors for optical system of IR cameras

IR optical systems such as Petzval doublet refractive lenses or Cassegrain reflective mirrors are either expensive or poor in image quality. Taking advantage of the low cost of reflective mirrors, here we present an optical design of Double Cassegrain reflective mirrors consisting of two sets of Cassegrain reflectors facing each other symmetrically. This symmetry also cancels many aberrations besides the chromatic aberration-free nature of reflective mirrors. Design results show that this system is better than Cassegrain reflectors in aberration correction and image resolution, but cheaper than Petzval doublet refractive lenses systems in price. IR cameras with this optical system could be widely used for body temperature measurement and security check.     

红外耦合光学系统设计

红外目标模拟器由红外目标图像发生器和投影光学系统组成。该红外光学系统是一个要求与2个导引光学系统的光学技术参数相匹配的长焦距、大视场和具有像方远心光路的中红外光学系统。叙述用于红外目标模拟器的红外耦合光学系统的设计原理，提出它与导引光学系统一起可组成放大倍率M=4.5×的红外投影光学系统，并指出IR CRT产生的图像通过红外投影光学系统可成像在导引接收器上。针对给出的红外耦合光学系统的设计特点和技术要求，光学材料选取硅（Si） 锗（Ge） 硅（Si），采用简单的柯克三片式结构完成光学系统设计。设计评价结果表明，该系统的光学性能和成像质量均满足设计指标要求。     

Using diffractograms to evaluate optical systems with coherent illumination

A new approach to measuring aberrations of an optical system with coherent illumination is introduced. The optical system is evaluated by use of a so-called weak phase object and by digital image recording and processing. Based on the contrast transfer function theory for coherent systems, the main aberrations of the optical system can be determined. This is a convenient approach to evaluating and measuring complex optical systems with numerous optical elements after assembly and can serve as a simple performance test of an optical instrument in the field.     

Binary phase only filters for rotation and scale invariant pattern recognition with the joint transform correlator

The joint transform correlator (JTC) is one of the two main optical image processing architecture which provides a highly effective way of comparing images in a wide range of applications. Traditionally, an optical correlator is used to compare an unknown input scene with a pre-captured reference image library, to detect if the reference occurs within the input. Strength of the correlation signal decreases rapidly as the input object rotates or varies in scale relative to the reference object. The aim of this paper is to overcome the intolerance of the JTC to rotation and scale changes in the target image. Many JTC systems are constructed with the use of ferroelectric liquid crystal (FLC) spatial light modulators (SLMs) as they provide fast two-dimensional binary modulation of coherent light. Due to the binary nature of the FLC SLMs used in the JTC systems, any image addressed to the device need to have some form of thresholding. Carefully thresholding the grey scale input plane and the joint power spectrum (JPS) has significant effect on the quality of correlation peaks and zero order (DC) noise. A new thresholding technique to binarise the JPS has been developed and implemented optically. This algorithm selectively enhances the desirable fringes in the JPS which provide correlation peaks of higher intensity. Zero order noise is further reduced when compared to existing thresholding techniques.Keeping in mind the architecture of the JTC and limitations of FLC SLMs, a new technique to design rotation and scale invariant binary phase only filters for the JTC architecture is presented. Filers design with this technique have limited dynamic range, higher discriminability among target and non-target objects, and convenience for implementation on FLC SLMs. Simulation and experiments shows excellent results of various rotation and scale invariant filters designed with this technique. A rotation invariant filter is needed for various machine vision applications of the JTC. By fixing the distance between camera and input object, the scale sensitivity of the correlator can be avoided. In contrast to the industrial machine vision applications, scale factor is very important factor for the applications of the JTC systems in defence and security. A security system using a scale invariant JTC will be able to detect a target object well in advance and will provide more time to take a decision.     

光学稀疏孔径系统的成像及其评价方法

对典型阵列结构的光学稀疏孔径系统成像特性进行了数值仿真分析,并采用基于光学实验测量的调制传递函数（MTF）完成了光学稀疏孔径系统成像实验的图像复原处理.针对复杂目标成像,为了评价光学稀疏孔径系统最终成像的整体质量,不仅考虑系统的调制传递函数指标,还提出了一种基于相关系数的成像质量客观评价方法.数值仿真结果和光学实验结果均表明,基于相关系数的成像质量客观评价方法是可行的,实验说明光学稀疏孔径系统成像质量可以达到其等效单个大孔径成像系统的成像效果.