Compression of Chinese document images based on morphologic analysis and pattern matching

We propose a highly efficient content-lossless compression scheme for Chinese document images. The scheme combines morphologic analysis with pattern matching to cluster patterns. In order to achieve the error maps with minimal error numbers, the morphologic analysis is applied to decomposing and recomposing the Chinese character patterns. In the pattern matching, the criteria are adapted to the characteristics of Chinese characters. Since small-size components sometimes can be inserted into the blank spaces of large-size components, we can achieve small-size pattern library images. Arithmetic coding is applied to the final compression. Our method achieves much better compression performance than most alternative methods, and assures content-lossless reconstruction. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

Compression of Chinese document images based on morphologic analysis and pattern matching

We propose a highly efficient content-lossless compression scheme for Chinese document images. The scheme combines morphologic analysis with pattern matching to cluster patterns. In order to achieve the error maps with minimal error numbers, the morphologic analysis is applied to decomposing and recomposing the Chinese character patterns. In the pattern matching, the criteria are adapted to the characteristics of Chinese characters. Since small-size components sometimes can be inserted into the blank spaces of large-size components, we can achieve small-size pattern library images. Arithmetic coding is applied to the final compression. Our method achieves much better compression performance than most alternative methods, and assures content-lossless reconstruction. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

蒙特卡罗模拟四极阱中原子的参变激发

在中性原子的磁囚禁实验中,磁阱线圈的电流噪声会激发磁阱中的原子运动,势必对原子团的温度和寿命产生不可忽视的影响。对于非简谐阱,这种激发具有能量选择特性,它又取决于电流噪声的频谱分布。选择了实验中常用的四极阱为研究对象,用直接模拟蒙特卡罗方法来模拟四极阱中原子运动的参变激发现象,得到了原子温度与原子数损失随激发频率的变化关系,并进一步计算了两个共振峰处原子温度随调制时间和调制深度的变化曲线。此外,还研究了弹性碰撞速率对参变激发过程中原子温度上升的影响。这些结果对四极阱参变激发的实验有较好的参考价值。

Optical spectroscopy and energy transfer of Er3+/Ce3+ in B2O3-doped bismuth-silicate glasses

Ce3+ and B2O3 are introduced into erbium-doped Bi2O3-SiO2 glass to enhance the luminescence emission and optic spectra characters of Er3+. The energy transfer from Er3+ to Ce3+ will obviously be improved with the phonon energy increasing by the addition of B2O3. Here, the nonradiative rate, the lifetime of the I-4(11/2) -> I-4(3/2) transition, and the emission intensity and bandwidth of the 1.5 mu m luminescence with the I-4(13/2) -> I-4(5/2) transition of Er3+ are discussed in detail. The results show that the optical parameters of Er3+ in this bismuth-borate-silicate glass are nearly as good as that in tellurite glass, and the physical properties are similar to those in silicate glass. With the Judd-Ofelt and nonradiative theory analyses, the multiphonon decay and phonon-assisted energy-transfer (PAT) rates are calculated for the Er3+/Ce3+ codoped glasses. For the PAT process, an optimum value of the glass phonon energy is obtained after B2O3 is introduced into the Er3+/Ce3+ codoped bismuth-silicate glasses, and it much improves the energy-transfer rate between Er3+ I-4(11/2)-I-4(13/2) and Ce3+ F-2(5/2) -> F-2(7/2), although there is an energy mismatch. (c) 2007 Optical Society of America.

双染料敏化的光致聚合物全息特性研究

报道了一种新型、双染料共同敏化的光致聚合物材料,该材料以丙稀酰胺和双丙稀酰胺作为单体,聚乙烯醇为聚合物基质,两种染料曙红Y和亚甲基蓝作为光引发剂.实验结果表明,该材料在四种波长的激光照射下,其最大衍射效率均不低于25%,最大可达54.8%.通过采用多波长存储技术,分别利用四种不同波长的光在该聚合物膜上同一位置存储了四幅不同的图像,取得一定的效果.

Laser pulse induced bumps in chalcogenide phase change films

Formation of bumps in chalcogenide phase change thin films during the laser writing process is theoretically and experimentally investigated. The process involves basically fast heating and quenching stages. Circular bumps are formed after cooling, and the shape and size of the bumps depend on various parameters such as temperatures, laser power, beam size, laser pulse duration, etc. In extreme cases, holes are formed at the apex of the bumps. To understand the bumps and their formation is of great interest for data storage. In the present work, a theoretical model is established for the formation process, and the geometric characters of the formed bumps can be analytically and quantitatively evaluated from various parameters involved in the formation. Simulations based on the analytic solution are carried out taking Ag8In14Sb55Te23 as an example. The results are verified with experimental observations of the bumps. (C) 2008 American Institute of Physics.

Cr^4＋：YAG被动调QNd：YAG陶瓷激光器的研究

介绍了近几年迅速发展的一种新型激光介质——透明Nd：YAG多晶陶瓷的发展状况，对比分析了多晶陶瓷与单晶的光谱特性、激光特性和连续实验研究情况。并对钛宝石激光器调谐至808nm，端面抽运Nd：YAG陶瓷被动调Q全固态激光器的脉冲运转进行了较为详细的理论分析和实验研究。采用初始透射率为90％的Cr^4＋：YAG可饱和吸收晶体，被动调Q的阈值功率为119mW，当端面抽运功率为465mW时，获得波长为1064nm，脉宽为16ns，重复频率为18．18kHz，单脉冲能量为3．4μJ，平均输出功率为61mW的稳定调Q

国产掺镱双包层光纤的激光特性

采用MCVD方法研发了掺镱双包层光纤，并对其结构特性、荧光特性和激光特性进行了测试和研究。其D形内包层尺寸为400／450μm，数值孔径为0．36，纤芯直径约为16μm，数值孔径约为0．18。荧光谱线的范围为1000-1140nm，1030nm处的峰宽大于50nm。采用大功率激光二极管单端泵浦6m长的双包层光纤，在泵浦人纤功率为61W时，获得了32W的激光输出，斜率效率为64％。该光纤在高功率处未发现饱和现象，通过优化光纤参数与泵浦方式还可以提高转化效率和输出功率。实验表明该光纤可以取代进口光纤用作高功率

色散管理孤子传输特性分析

色散管理孤子光波系统的色散图周期由具有正负色散值的两段光纤组成，并且在系统中周期性放置集中放大器及滤波器装置。采用变分法获得了描述此种系统性能的常微分方程组，并利用这组方程数值研究了各种参量对孤子传输性能的影响。研究结果表明，虽然从整体趋势上看，当要求色散管理孤子有较好的稳定性时，应适当降低系统的色散管理强度，但在一定条件下，调整光纤放大器的位置以及正负色散光纤的色散差值，可同时获得相对较大的色散管理强度和好的孤子稳定性；总体来讲，集总放大器的位置会对孤子传输的稳定性、色散管理孤子的能量增强因子、脉冲最佳

初始啁啾对光纤中传播的飞秒光孤子的影响

采用分步傅里叶变换作为数值模拟的方法，以二阶飞秒光孤子和基态飞秒光孤子为例，讨论了初始啁啾对光纤中传播的飞秒光孤子的时域特征和频谱结构的影响，概括出如下的结论：初始啁啾通过影响飞秒光孤子谱线的红移，而对飞秒光孤子由拉曼效应引发的脉冲延迟产生较大影响，正的初始啁啾使脉冲延迟加剧，负的初始啁啾使脉冲延迟减小。

A New theory for evaluating the number density of inclusions in films

A new formulation derived from thermal characters of inclusions and host films for estimating laser induced damage threshold has been deduced. This formulation is applicable for dielectric films when they are irradiated by laser beam with pulse width longer than tens picoseconds. This formulation can interpret the relationship between pulse-width and damage threshold energy density of laser pulse obtained experimentally. Using this formulation, we can analyze which kind of inclusion is the most harmful inclusion. Combining it with fractal distribution of inclusions, we have obtained an equation which describes relationship between number density of inclusions and damage probability. Using this equation, according to damage probability and corresponding laser energy density, we can evaluate the number density and distribution in size dimension of the most harmful inclusions. (c) 2005 Elsevier B.V. All rights reserved.

离子束溅射法薄膜生长中结瘤微缺陷的生长机理

用离子束溅射法制备了锆单层薄膜．用设计新型夹具和预置种子方法，对薄膜中结瘤微缺陷的生长过程进行了研究．在高分辨率光学显微镜和扫描电子显微镜下观察发现，结瘤在其生长初期呈现出分形的特征．用分子动力学和薄膜生长的扩散限制聚集模型，薄膜中结瘤微缺陷成核时的分形现象得到了很好的解释．

Design and properties analysis of multi-layer dielectric used in pulse compressor gratings

Used in chirped-pulse amplification system and based on multi-layer thin film stack, pulse compressor gratings (PCG) are etched by ion-beam and holographic techniques. Diffraction efficiency and laser-induced damage threshold rely on the structural parameters of gratings. On the other hand, they depend greatly on the design of multi-layer. A theoretic design is given for dielectric multi-layer, which is exposed at 413.1 nm and used at 1053 nm. The influences of coating design on optical characters are described in detail. The analysis shows that a coating stack of H3L (H2L) (boolean AND) 9H0.5L2.01H meets the specifications of PCG well. And there is good agreement of transmission between experimental and the theoretic design. (c) 2005 Elsevier GmbH. All rights reserved.

光波在具有柱状结构的双折射薄膜中的传输特性

根据电磁场理论的矩阵分析方法推导了光波在具有柱状结构的双轴薄膜中的反射系数、透射系数和相位关系等光学特性。这些关系包含了界面处的多点反射，可以推广到一般的各向异性的多层膜系统。给出了各向同性入射媒质一双轴各向异性膜层一各向同性基底薄膜系统的计算结果，验证了该计算方法的可行性，为双折射多层膜结构及其器件的理论分析和设计提供了理论参考。

单脉冲飞秒脉冲激光对单层和高反光学薄膜的损伤

用电子柬蒸发的方法在BK7玻璃上制备了ZrO2单层膜和ZrO2／SiO2高反膜，利用掺Ti：sapphire飞秒激光系统输出的中心波长为800nm，脉宽为50fs的激光脉冲对这两种样品进行了激光损伤阈值测试．实验结果表明，ZrO2单层膜的阂值比ZrO2／SiO2高反膜的高；这与传统的纳秒脉冲激光的损伤情况相反．利用光离化和碰撞离化激发电子到导带，形成电子等离子体基本模型并对此现象进行了解释．同时，用显微镜对样品的损伤形貌进行了观测，对损伤的特点进行了表征．