波分复用改善光纤传象束象质的导模分析

运用光纤导模（束缚模）理论和离散抽样理论分析了光纤象束象的质量，估算了决定波分复用象束系统象质的信息量Ｎ，Ｎ是到达象面的而且有与物场相位分布几乎相同的场模数，并估算了波分复用技术改善光纤象束系统象质的倍增率。     

光纤望远系统设计

结合以大截面光纤传象束作为中继传象元件的光纤望远镜研制，阐述了光纤望远系统的组成和成象原理；提出了为实现系统具有较高的光学性能，良好的传象质量，在设计上应作的考虑和措施，其中包括系统光学参数确定和结构的选择，此外，还讨论了光纤望远系统中的一些特殊问题，如光束限制，调焦及象质改善等。     

束状光波大气传输源象抖动时间频谱

本文研究了通过湍流大气传输束状光波在接收光学系统象面上成象位置抖动方差和抖动时间频谱。得到了包含风速因子υ_⊥且适用于全部湍流起伏区的抖动方差和象点抖动频谱的一般关系式。     

扩展目标高分辨力斑点成象的模拟

介绍了扩展目标高分辨力斑点成象过程的计算机模拟,内容包括大气湍波的模拟、目标短曝光象的形成、目标功率谱的估计、目标傅里叶相位的恢复以及克服大气湍流影响后目标高分瘁力图象的重建。模拟结果显示,斑点成象技术可以克服大气湍流的影响,获得了望远镜口径决定的衍射极限的成象分辨力。模拟所建立的系统,也为进一步深入研究扩展目标的高分辨力斑点成象技术打下了基础。     

材料科学研究中电子显微学的成功应用（续）

3　高分辨电子显微技术在纳米结构研究中的应用在叙述高分辨电子显微技术 (HREM)应用的若干具体例子之前 ,首先指出常规电子显微技术(CVEM)与 HREM之间最基本的区别在于 CVEM只用一个电子束 (直接透射束或者衍射束 )成象 ,而HREM允许使用包括直接透射束在内的许多衍射束穿过物镜光阑成象。图 1 5简要地表示了使用CVEM明场 (a)、暗场 (b)成象以及 HREM成象 (c)方式。贡献于成象的斑点数目越多 ,图象质量愈佳。当然 ,可用的斑点数目也会受到电子显微镜物镜球差的限制。我们现在常取大约 1 0个斑点来获得HREM象。 HREM观察的其…     

自聚焦透镜列阵象平面上照度分布的分析

研究了自聚焦透镜及其列阵象平面上的照度分布。讨论只限于近轴射线单位放大率成象的条件下。一列和二列的自聚焦透镜列阵在场扫描和线扫描光学成象系统中,象面上光强分布将有所不同。因此,我们作了分析,并对某些样品进行了测量。     

智能化自动回零检测系统

本文从基本理论出发，设计了一套多学科综合应用的检测系统。应用象分析器和狭缝成象理论以及计算机技术，完成自动回零检测工作。     

一种载波抑制调制波分复用系统的仿真与分析

本文对载波抑制波分复用ROF系统模型进行了仿真分析。首先基于文献实验，实现了单路载波抑制的ROF系统模型，然后对载波抑制波分复用系统分别进行了仿真分析。结果表明，以误码率10^-9为标准，传输30km后，载波抑制调制的波分复用系统传输性能下降大约4dbm，由于可以提高系统的信道利用率，该系统仍然适合较远距离传输。     

电影六分仪跟踪望远镜用的70毫米画幅像增强器

大型75毫米画幅贴近聚焦象增强器可以提供高的光放大,高的成象质量和高速电子快门的功能。这些增强器业巳安装在静止摄影机和电影摄影机系统中。本文叙述贴近聚焦象增强器最近在70毫米电影摄影机系统中应用的情况。讨论了该系统的设计考虑,验收试验和一些缺点。建议使用直接接触象增强摄影术和高速电子快门技术加以改进。     

用点扩展函数确定卫星反射后的脉冲强度

卫星激光测距系统是一个非相干成象光学系统。卫星形状效应是由于卫得上不同位置的反射器对光子反射的时间不同而引起的脉冲强度重新分布的现象。非相干成象系统在等晕区内是空间不变性的光强线性系统。成象光学系统中象强度等于输入物强度与光瞳点扩展函数的卷积。用卫星的点扩展函数描述卫星形状效应,能非常简便地计算出被卫星反射后的脉冲强度分布。讨论了激光测距卫星的点扩展函数的求解方法和表达形式,并分别推导和计算了Lageos卫星和自行设计卫星的点扩展函数以及点扩展函数作用后的脉冲强度分布。     

Two-dimensional image transmission through a single optical fiber by wavelength-time multiplexing

Serial transmission of image data through an optical fiber is inefficient in the utilization of the channel capacity of the fiber. Parallel image transmission techniques, on the other hand, generally limit the transmission length to a few meters. A novel approach is introduced with which 2-D image data can be transmitted efficiently at high speed over a single optical fiber using wavelength-time multiplexing. Several system configurations designed for different types of input are presented.     

Angle-multiplexed holographic data storage with minimum cross talk noise

The cross talk noise-to-signal ratio (NSR) of an angle-multiplexed holographic data storage system is studied, and we propose a method to determine the optimized multiplexing spacing with which the cross talk noise can be less than the conventional method. In our method, the optimization location at the image plane can be chosen arbitrarily, so the multiplexing of asymmetrical image patterns can be optimized. In particular, we investigate the 90° scheme and the transmission scheme angle multiplexing. For the 90° scheme, a holographic medium with a higher refractive index is recommended for cross talk-limited multiplexing. For the transmission scheme, a holographic medium with a lower refractive index is recommended for angular range-limited multiplexing. In addition, for the transmission scheme, a larger angle between the object arm and the reference arm results in less cross talk noise, whereas the highest storage density is achieved at a 45° angle.     

Resolution improvement in digital holography by angular and polarization multiplexing

Angular and polarization multiplexing techniques are utilized in both object and reference arms in the digital holographic microscopy system to improve its resolution. The angular multiplexing provides on-axis and off-axis illumination and reference beams with different carrier frequencies. Polarization multiplexing prohibits the occurrence of interference between low and high object spatial frequencies and reference beams. The proposed system does not require special light sources or filtering masks. Experimental results show that the resolution of the synthesized image exceeds the resolution determined by the numerical aperture of the imaging microscope objective.     

Fast multispectral diffuse optical tomography system for in vivo three-dimensional imaging of seizure dynamics

We describe a multispectral continuous-wave diffuse optical tomography (DOT) system that can be used for in vivo three-dimensional (3-D) imaging of seizure dynamics. Fast 3-D data acquisition is realized through a time multiplexing approach based on a parallel lighting configuration--our system can achieve 0.12 ms per source per wavelength and up to a 14 Hz sampling rate for a full set of data for 3-D DOT image reconstruction. The system is validated using both static and dynamic tissue-like phantoms. An initial in vivo experiment using a rat model of seizure is also demonstrated.     

Identification data reproduction in multilayered optical waveguide-type holographic memory cards

The identification (ID) data reproduction was computationally examined for the compatibility with the aperture multiplexing and the telecentric system. The mask for the multiplexing caused shade in the reproduced ID data cell. The shading tolerance was improved by modulating the phase of the original image so that the ID data holograms diffract the light in the oblique direction or with the concentrating. The telecentric system reproduced all ID data cells in the same position of the image sensor and made a distinction among the cells impossible. This was solved by reproducing the cell point symmetrically from the corresponding ID data hologram in each 3x3 ID data block.     

Storage of 1000 holograms with use of a dual-wavelength method

We demonstrate the storage of 1000 holograms in a memory architecture that makes use of different wavelengths for recording and readout to reduce the grating decay while retrieving data. Bragg-mismatch problems from the use of two wavelengths are minimized through recording in the image plane and using thin crystals. Peristrophic multiplexing can be combined with angle multiplexing to counter the poorer angular selectivity of thin crystals. Dark conductivity reduces the effectiveness of the dual-wavelength method for nonvolatile readout, and constraints on the usable pixel sizes limit this method to moderate storage densities.     

融合空频复用和近远场复用的多功能超表面图像显示

超表面可以在亚波长尺度上对光波的偏振、振幅、频率、相位等基本参量进行精确调控。基于此背景,本文提出并实验验证了一种融合空间频率复用和近远场复用的多功能超表面图像显示技术。其中,近远场复用是利用纳米结构的转角简并性将超表面几何相位调控与光波强度调控相融合,基于模拟退火算法实现近场灰度图像与远场全息图像的独立编码;空间频率复用是将两幅图像的不同空间频率成分叠加作为远场全息图像,可以在不同观察位置分别接收到不同的空间频率信息,对应高频图像和低频图像。实验结果表明,通过优化超表面可以同时在不同工作距离实现三幅独立图像(灰度图像、高频图像及低频图像)的显示,这提升了超表面的信息存储容量。本工作将为超表面多功能复用及其在光学加密、光学防伪等领域的应用提供新思路。

     

Four-Channel, 8 x 8 Bit, Two-Dimensional Parallel Transmission by use of Space-Code-Division Multiple-Access Encoder and Decoder Modules

We experimentally demonstrate four-channel multiplexing of 64-bit (8 x 8) two-dimensional (2-D) parallel data links on the basis of optical space-code-division multiple access (CDMA) by using new modules of optical spatial encoders and a decoder with a new high-contrast 9-m-long image fiber with 3 x 10(4) cores. Each 8 x 8 bit plane (64-bit parallel data) is optically encoded with an 8 x 8, 2-D optical orthogonal signature pattern. The encoded bit planes are spatially multiplexed and transmitted through an image fiber. A receiver can recover the intended input bit plane by means of an optical decoding process. This result should encourage the application of optical space-CDMA to future high-throughput 2-D parallel data links connecting massively parallel processors.     

高速多光谱TDICCD图像数据传输系统

为了解决高速多通道CCD应用时数据传输路数多、数据率高的问题,研制了高速多光谱TDICCD的图像数据传输系统,并在实际工程应用中取得良好效果.阐述了系统总体设计思想和FPGA实现方案,并对FPGA功能划分、时分复用存储及LVDS接口等设计要点进行详细分析,最终系统实现了5片TDICCD共60通道并行图像数据转7路串行图...