自聚焦

The results are detailedly compared with those of commercial application using aspherical cylindrical lens.

对自聚焦光纤透镜的原理进行了分析，综合考虑到自聚焦光纤透镜的焦距和端面研磨的方便，确定了实验中自聚焦光纤透镜的长度。

Based on the traits of the aspherical lens, the sunlight was focused on a very small spot, and then it was transferred into a plastic fiber by an aspherical lens and a selfoc lens. A formula for calculating the optimal length of selfoc lens is presented. The optimal assembly of the aspherical lens and selfoc lens was implemented by the aid of this formula. Therefore, sunlight is coupled into a plastic fiber efficiently.

根据非球面透镜垂轴球差小的特点把太阳光会聚到很小的光点，再利用长度约为1/4节距的自聚焦透镜改变光线的数值孔径使其满足光纤的数值孔径，通过一个计算公式来计算最佳的自聚焦透镜长度，实现非球面透镜和自聚焦透镜的最佳组合，把太阳光以较高的耦合效率耦合进塑料光纤。

We put it across that the sign of nonlinear refractiveindex changes under certain conditions if the high-order excited state contributessignificantly to the refractive index.The nonlinearity changes from self-defocusing to self-focusing if the refrangibility of the ground state is larger thanthat of the first excited state and smaller than that of the second excited state.

高阶激发态折射度贡献较大时，非线性折射率符号在一定条件下存在转化：如果基态折射度大于低阶激发态的折射度而小于高阶激发态折射度，材料发生自散焦—自聚焦转化；如果基态折射度小于低阶激发态折射度大于高解阶激发态折射度则发生自聚焦—自散焦转化。

And images processed with the incorrect parameters will be worsened. This paper analyses the effect of SNR on autofocus and proposes an adaptive filter in SAR azimuth subsampling to keep SNR as high as possible, so that the performance of autofocus can be improved and higher image quality achieved.

该文分析了信噪比对自聚焦的影响，提出利用自适应滤波器来做方位向预滤波和降采样，在降低采样率的同时，保持原始图像的信噪比，再经有效的自动聚焦算法，得到较准确的多普勒参数估计值，从而获取高分辨率SAR图像。

Our main work is as follows: the stable laser mode theory in uniform plasmas is extended to non-uniform plasma cases; the discussion of the sufficient and necessary conditions for laser self-focusing in uniform plasmas is developed to non-uniform plasma cases; a quantitative approach to judge the impact of different plasma density distribution on laser self-focusing is proposed; the evolution properties of asymmetric laser filed in non-uniform and uniform plasmas are discussed and mechanisms that symmetric channel-like plasmas can confine the laser centroid around the plasma channel axes and symmetrize initially asymmetric laser beams are proposed; the formation of solitary standing wave in moderate plasma density is studied by PIC simulations and can be explained by stimulated Raman scattering of laser beams in plasmas.

主要工作为：把均匀等离子体中激光的稳定模理论推广到横向非均匀等离子体情形；把均匀等离子体中激光自聚焦的充分和必要条件的讨论推广到横向非均匀等离子体情形；给出横向密度分布不同的等离子体影响激光自聚焦的定量判据。讨论了初始不对称的激光场在横向非均匀及均匀等离子体中的演化特性，并提出了具有对称腔道结构的等离子体箍缩激光质心和对称化初始不对称激光场的物理机制。用粒子模拟讨论了激光场在等离子体中形成孤立驻波的过程，认为前向受激拉曼散射是发生此现象的可能机制。

We use GRIN lens as collimating or focusing lens for transmission gas cell ,and a method that using cascaded GRINLens couple to increase the optical path length is presented. Using this method ,the detection sensitivity of the gas cell has been greatly increased.

利用自聚焦透镜作为光纤准直透镜和聚焦透镜，应用于透射型气室，并提出了在透射式气室中将多对自聚焦透镜组串联用以增加吸收光程的方法，用该方法可以明显提高气室的检测灵敏度。

This paper analyzed the advantage and disadvantage of three sound wave focus methods, that is lens focus, curved autofocus, and phased-array focus on the base of draw lessons from supersonic focus technic, consequently preferred and designed the infrasonic phased-array focus system.

文中在借鉴超声波聚焦技术的基础上，分析了透镜聚焦、曲面自聚焦、相控阵聚焦等三种声波聚焦方法的利与弊，从而选用和设计了次声相控阵聚焦系统。

It is very important to reveal the characteristic of nonlinear small-scale self-focusing of broadband laser experimentally, and it is also of great theoretical and practical significance for the development of high-power laser system.

本文在利用解析和数值方法研究宽带激光自聚焦规律的基础上，通过搭建具体的实验平台，进一步从实验上研究了宽带激光小尺度自聚焦的动态传输过程。

Meanwhile the relativistic effect has also been considered, the result shows that it's different from the relativistic self-focusing of long laser pulse.

结果表明，相对论效应的计入虽然增加了体系的非线性度，但与长脉冲激光中的相对论自聚焦效应不一样的是，它减弱了非线性效应对自聚焦的影响。

The self-focusing properties, design, fabrication and diffraction properties of Varied Line-Space grating were investigated in detail.

利用变栅距光栅的衍射光束自聚焦特性，设计和制作了变栅距透射光栅，并对其自聚焦特性进行了研究。

I didn't watch TV last night, because it .

昨晚我没有看电视，因为电视机坏了。

Since this year, in a lot of villages of Beijing, TV of elevator liquid crystal was removed.

今年以来，在北京的很多小区里，电梯液晶电视被撤了下来。