Laboratory demonstration of spotlight-mode down-looking synthetic aperture imaging ladar

We present a tabletop-scale spotlight-mode down-looking synthetic aperture imaging ladar(DL SAIL) demonstrator, which is performed by a collimator with 10 m focal length to simulate the far-field optical field.A specular-point target and a diffuse-reflection target have been used for resolution analysis and 2D imaging,respectively. The experimental result is in agreement with the theoretical design. The experiment setup is capable of simulating a real application scenario for further study. This Letter is focused on the proposition and implementation of spotlight-mode DL SAIL.     

光学合成孔径成像技术发展概况

介绍了光学合成孔径成像技术的发展现状。简要阐明了合成孔径成像技术的原理和分类以及在光学波段的主要应用。归纳出了光学合成孔径成像技术的发展趋势:地基合成孔径系统向长基线方向发展;天基系统向超轻量化方向发展;图像处理正在成为系统不可分割的一部分;技术重点是从地基系统向天基系统转移,并被应用于更多领域。概括了光学合成孔径成像系统的各种应用方案及特点。与传统的光学系统相比,合成孔径成像技术具有如下特征和优点:可降低光学元件的加工难度和天基光学合成孔径成像系统的发射体积和重量,可节约发射费用。     

Current status on the contribution of silica fibres to stellar interferometry

This paper reports on guided and integrated optics set-ups developed in our laboratory in the framework of aperture synthesis for astronomy. After summarising the function required to design a stellar interferometer, we propose guided components for these purposes. The implementation of these components is illustrated by two examples of interferometers with a view to using guided components as often as possible and testing an end-to-end imaging demonstrator.     

The system design and assemble for the high resolution telescope system with segmented aperture

A design method along with its results, for a space optical system with high resolution and wide field of view, is described. Such optical systems can be used in the infrared as well as visible configurations. The proposed design is based on an on-axis Ritchey-Chrétien system with corrected lens element while the primary mirror is a segmented aperture. Here the on-axis concept allows wide-field enabling a variety of observations designed for the multi-object spectrometer instruments, optimized for low scattering and low emission of light. The use of segmented mirrors in the optical system allows adopting any method for its fabrication purposes. Segment results are discussed and the image quality of the design based on these results is evaluated in this paper.     

基于集成分析法的光机热一体化设计

光机热一体化设计是改进空间光学仪器设计,优化系统总体设计参数的重要方法。集成分析法对设计方案综合性能的动态评估是一体化设计的核心,通过分析系统热光学性能,指导修改设计参数,实现系统光/机/热同步设计。以某空间光学仪器主镜系统的热控设计为例,介绍了这种方法在实际工程中的应用。     

具有实入瞳的远心离轴三反系统研究与设计

采用远心离轴三反成像系统的空间遥感仪器前有光束限制装置时,要求系统具有实入瞳与之匹配。为了满足这一需要,研究了孔径光阑位于主镜前与系统物方焦平面重合的离轴三反系统的设计问题,推导了主镜和三镜共面时离轴三反系统结构参数计算式及物方焦点与主镜间隔表达式,确定了实现系统物方焦点为实焦点的条件及其解法。据此,针对光谱范围为1.0～2.5μm、F数为4、有效焦距为360mm、视场为5°的设计要求,设计出整个波段全视场像质接近衍射极限的具有实入瞳的远心离轴三反系统,系统非球面最高次数为4次。设计结果表明,这种设计方法可用于实入瞳远心离轴三反成像系统的设计。     

Down-looking synthetic aperture imaging ladar demonstrator and its experiments over 1.2 km outdoor

We present a down-looking synthetic aperture imaging ladar demonstrator and its experiments over 1.2 km in the field. The achieved imaging resolution is in agreement with the theoretical design, and the resulting two-dimensional image is satisfied. The capability to eliminate the influence from atmospheric turbulence is fully proven by the experiments.     

Velocity measurement by the laser speckle method using optical fibres

An optical device for in-plane velocity measurement is described. Laser light is focused by the use of an optical fibre onto the object, and the device utilizes the dynamic sparkle effect for velocity determination. The influence of different optical fibres on the speckle formation is investigated with special respect to fibre movement, and as the diameter of the aperture used for speckle detection also affects the measuring signal, an optimum value is found. A simple electronic circuit processes the measuring value proportional to the object velocity.     

Subdiffraction‐limited chemical imaging of patterned phthalocyanine films using tip‐enhanced near‐field optical microscopy

A tip‐enhanced near‐field optical microscope, based on a shear‐force atomic force microscope with plasmonic tip coupled to an inverted, confocal optical microscope, has been constructed for nanoscale chemical (Raman) imaging of surfaces. The design and validation of the instrument, along with its application to near‐field Raman mapping of patterned organic thin films (coumarin‐6 and Cu(II) phthalocyanine), are described. Lateral resolution of the instrument is estimated at 50 nm (better than λ/10), which is roughly dictated by the size of the plasmonic tip apex. Additional observations, such as the distance scaling of Raman enhancement and the inelastic scattering background generated by the plasmonic tip, are presented. Copyright © 2016 John Wiley & Sons, Ltd.     

Comprehensive modelling and optical analysis of single-lens telescopes

Classical refractors require at least two lenses, an objective and an eyepiece, to achieve image magnification and focusing. In this study, a minimalistic telescope design consisting of a single lens and a small aperture (the single-lens telescope) is examined. The design exploits the angular limiting properties of the aperture to achieve approximate image focusing, at the expense of image brightness. An analytical geometrical optics model is first presented to explore the fundamental optical properties of such a system, alongside a numerical ray-tracing framework; a more general Fourier optics theory unifying both diffractive and geometrical regimes is also developed. Extensive experimental validation of theoretical results across angular magnification, angular resolution, and image intensity profiles is demonstrated, and optimum aperture sizes for varying magnifications and irradiance wavelength are derived. The mechanical simplicity of such telescopes indicates good applicability as a simple and low-cost instrument for beginner astronomy or ad-hoc fieldwork.     

Optical clock distribution with a compact free space interconnect system

Optical clock signal distribution has been widely discussed to be an attractive way to reduce the clock skew in high-speed digital systems. For short interconnect lengths, especially for chip level clock distribution, free space systems using diffractive optical elements (DOEs) have specific advantages. The optoelectronic pathway described in this paper consists of a GaAs laser diode, a microetched silicon mirror, a faceted diffractive element and four silicon photodiodes hybridized to a (dummy) silicon chip. The key element of the clock distribution demonstrator is the diffractive element which matches setup requirements like compactness, off-axis geometry and use of an unshaped laser beam. The whole setup meets the demands of alignment accuracy in an excellent way. This is achieved by the very good imaging characteristic of the DOE and by an alignment technique based on precision mounting of micromachined silicon components. The system was tested with clock rates up to 2.5 GHz, the cut-off frequency is 350 MHz.     

激光全息演示仪

为了在不具备昂贵的全息防震台和完备的光学器件的条件下,也能有一种比较理想的教学仪器,能够实现各种全息像的再现演示,本文介绍了这种激光全息演示仪的原理和结构设计。     

小型化望远式激光共焦扫描显微内窥镜

研制了一种激光共焦扫描显微内窥镜,采用望远式显微内窥光学系统,同时实现长距离的图像中继传输、远心f-theta光学扫描和显微内窥成像功能.二维共焦扫描由双振镜实现,低噪音扫描控制信号由嵌入式系统产生.为实现便携式应用,激光共焦扫描显微内窥镜采用小型化设计方案.首先,体内的显微内窥成像光学系统,外径尺寸为8 mm,工作长度为250.3 mm,可通过标准腹腔镜手术孔进行体内显微内窥成像;其次,采用3 mm通光孔径的小尺寸平面反射镜实现体外共焦扫描,摆动频率为100 Hz,实现快速共焦扫描;最后,激光控制和荧光探测仅通过电缆和光纤与共焦扫描显微内窥镜前端连接,减小了显微内窥镜的前端尺寸和重量.通过实验验证,本系统的成像视场为φ 600 μm,光学分辨率为2.2 μm,可采用手持式或者其他方式工作,进行体内组织的共焦扫描成像,实现微创、在体的荧光显微内窥术.     

极大口径光学望远镜凸非球面副镜的补偿检测法研究

提出了一种检测大口径、快焦比凸双曲面反射镜的补偿检验方法,补偿系统由一组小透镜和一块大口径反射标准镜组成,标准镜的口径约为被检验镜的1.8倍,该方法为极大口径光学望远镜凸非球面副镜的检验提供了一种有效的解决方案。以美国30 m望远镜（TMT）3.1 m,F/1的凸双曲面副镜为例,进行了补偿光路的设计优化。设计结果表明,该方法可以直接检测到直径达3.1 m的大口径、快焦比凸双曲面副镜的整个表面质量,补偿系统像差被校正得很好,PV值约为/100,弥散斑直径在衍射极限范围内。     

现代航天光学成像遥感器的应用与发展

概述了当前航天光学成像遥感器在对地、对天观测的多个领域的应用现状,给出了国外著名高分辨率商业卫星的性能指标,归纳了在轨和即将发射的太空望远镜的工作参数,展望了以更高的地面分辨率、更宽的地面覆盖和更高成像质量为目标的高性能光学遥感器的发展方向。依托大型光学成像平台的模块化技术和天地一体化设计为代表的综合性光学遥感器,阐述了实现自动识别和在轨参数自动调整的智能型光学成像遥感器的可行性、环境条件和技术要求。总结了目前在航天光学成像遥感器设计中大口径、主动光学波前探测和在轨智能处理等方面的关键技术和实现难题,提出了可实现的研究思路和未来的发展前景。     

Crystal optics as guard apertures for coherent x-ray diffraction imaging

A crucial issue in coherent x-ray diffraction imaging experiments is how to increase the signal-to-noise ratio when measuring relatively weak diffraction intensities from a nonperiodic object. A novel crystal guard aperture is described that makes use of a pair of multiple-bounce crystal optics to eliminate unwanted parasitic scattering background. This background is often produced by upstream optical elements such as a coherent-beam defining aperture. Recent experimental observation and theoretical analysis confirm the effectiveness of the crystal guard aperture method with coherence-preserved wave propagation through the crystal guard aperture and dramatically reduced scattering background in coherent x-ray diffraction images.     

Image degradation characteristics and restoration based on regularization for diffractive imaging

The diffractive membrane optical imaging system is an important development trend of ultra large aperture and lightweight space camera. However, related investigations on physics-based diffractive imaging degradation characteristics and corresponding image restoration methods are less studied. In this paper, the model of image quality degradation for the diffraction imaging system is first deduced mathematically based on diffraction theory and then the degradation characteristics are analyzed. On this basis, a novel regularization model of image restoration that contains multiple prior constraints is established. After that, the solving approach of the equation with the multi-norm coexistence and multi-regularization parameters (prior’s parameters) is presented. Subsequently, the space-variant PSF image restoration method for large aperture diffractive imaging system is proposed combined with block idea of isoplanatic region. Experimentally, the proposed algorithm demonstrates its capacity to achieve multi-objective improvement including MTF enhancing, dispersion correcting, noise and artifact suppressing as well as image’s detail preserving, and produce satisfactory visual quality. This can provide scientific basis for applications and possesses potential application prospects on future space applications of diffractive membrane imaging technology.     

电脑测色配色仪光谱测色头设计

本文介绍了国产GK-02型电脑测色配色仪的光学系统设计及一些光谱测色系统选型的问题。选用并设计了C-T型单色器、光导纤维光度补偿装置,使系统达到比较好的象质和稳定性,结构紧凑,使用效果良好。     

反射式光纤共焦扫描成像的研究

建立了反射式光纤共焦扫描成像系统,分析了光纤－集光透镜参数Ａ及物透镜有效数值孔径等对系统成像分辨率的影响。并在此基础上选择了合适参数的透镜,获得了优化的反射式光纤共焦扫描成像系统,测试结果表明,该系统具有亚微米级横向成像能力,微米级向层析能力,成像稳定性那,它将应用于材料及生物组织三维成像检测中。     

光学综合孔径成像技术实验研究

根据光学综合孔径成像系统的成像质量与点扩散函数和光学传递函数的关系,以G o lay-3阵列结构为例,从空间域和频率域对光学综合孔径成像技术进行理论仿真和实验研究。在空间域从理论上分析光学综合孔径成像系统的点扩散函数,对复杂目标的成像通过目标函数与点扩散函数的卷积求得,点扩散函数决定了成像质量。通过数值仿真和模拟实验取得了点扩散函数强度分布图,两者分布规律一致证明理论分析正确。在频率域研究光学综合孔径调制传递函数,理论仿真和实验取得的调制传递函数表明,空间域和频率域内光学综合孔径成像技术的理论分析与实验结果具有较好的一致性。