全息光栅曝光系统中空间滤波器孔径与激光束腰关系的选择方法

在全息光栅制作过程中, 由空气悬浮颗粒及光学器件缺陷引起的散射光会被记录在光刻胶上, 既影响光栅衍射效率, 又会带来光栅杂散光. 为消除系统散射光, 需要对激光光束的高频成分进行滤波处理. 但是, 激光光束通过空间滤波器后发生衍射, 进而影响干涉场质量, 因此选择合适的空间滤波器孔径是搭建全息光栅曝光系统的前提条件. 根据标量衍射积分理论, 通过卷积计算滤波光束的振幅分布分析光束的相位变化, 以光束相位突变位置远离光束中心为依据确定滤波器针孔半径与光束束腰半径的比值下限; 根据滤波光束的能量守恒关系, 通过滤波光束的高斯参数变化描述光束的衍射强弱规律, 以光束发生衍射的临界条件确定滤波器针孔半径与光束束腰半径的比值上限. 结果表明, 当空间滤波器针孔半径与激光束腰半径之比满足1.52< a/ω₀<2.2时, 滤波光束曝光区域相位恒定, 光束能量通过率大于99%, 在此区间空间滤波器滤波效果最好.     

基于参数辨识α-β-γ滤波的自适应调整跟踪窗算法

针对传统a-β-γ滤波器受跟踪精度与收敛速度之间的矛盾以及系数固定的影响而难以跟踪强机动性目标的局限性,设计了一种基于参数辨识的自适应的a-β-γ滤波跟踪器.该滤波器根据目标机动性的变化,利用跟踪误差调整模糊集系统的输出,在保证精度的前提下,得到自适应的系数值,使跟踪结果快速收敛,很好地解决了跟踪精度与收敛速度之间的矛...     

探求扇形内接矩形的面积最值

我们在教学中对一些有趣的教学题目应多加思考,注意发掘其中的信息,设计层层递进的“问题串”,逐步提出由浅入深的问题,让“问题”引领学生的思路,启发学生积极思考,激发求知欲,形成良好的思维品质,培养学生的创造思维能力．     

具有Markov跳变参数的广义系统鲁棒故障检测

针对一类广义不确定时滞Markov跳变系统,应用鲁棒控制理论分析重构的增广系统,获取了系统的故障检测滤波器.利用构造的随机Lyapunov-Krasovskii函数和线性矩阵不等式,证明并给出了故障检测滤波器有解的充分条件和优化设计方法,同时使得残差体现其对扰动的抑制作用和对故障的灵敏性.所设计的滤波器使系统具有随机稳定性,抑制干扰能力强,满足所给的范数指标.仿真算例对结果进行了验证,在故障信息发生时,故障检测滤波器可以很灵敏地检测出故障,并能有效地抑制未知扰动对残差的影响在给定的范围内.     

小型化大功率腔体滤波器技术研究

该文简述了小型化大功率腔体滤波器在雷达接收机中的应用及研制小型化大功率腔体滤波器的意义,分析了小型化大功率腔体滤波器的技术方案,以及对小型化大功率腔体滤波器所用滤波器的仿真,给出了S波段小型化大功率腔体滤波器的实例。     

Modular filter convergence theorems for Urysohn integral operators and applications

We prove some versions of modular convergence theorems for nonlinear Urysohn-type integral operators with respect to filter convergence. We consider pointwise filter convergence of functions giving also some applications to linear and nonlinear Mellin operators. We show that our results are strict extensions of the classical ones.     

一种基于复式光子晶体的多通道红外滤波器

用LiF和Si构成了一(ABBA)N型光子晶体,考虑到材料的色散关系,对其透射特性进行了研究,结果表明:在44~46μm的范围内出现了若干透射峰,透射峰的数目k与结构周期数N间满足k=N-1的关系。入射角增加,各透射峰的位置红移,长波端透射峰的红移量比短波端的稍大,当入射角θ≥45°时,短波端透射峰的透射率有所下降。两介质的几何厚度同时增加时,各透射峰的中心蓝移,对应的透射率不变;反之,其中心红移,且长波端透射峰的透射率下降。透射峰的以上特征为其实现多通道的红外滤波提供了理论指导。     

Laser 728 nm Spectroscopy of Electrodeless Discharge Rb Lamp

The electrodeless discharge rubidium vapor lamp plays a key role in a number of applications, such as atomic clock, atomic magnetometer, atomic optical filter and laser frequency stabilization. The electrodeless discharge Rb vapor lamp has rich spectra, including 420nm, 421nm, 565nm, 572nm, 607nm, 616nm, 728 nm, 776 nm, 780 nm, 795 nm, 1324 nm, 1344 nm, 1366 nm, 1475 nm, 1529 nm spectroscopy, etc. The 780nm transition wavelength between 5P3/2 and 5S1/2 of Rb atoms is usually used in fields of the Rb atomic clock and the Rb atomic magnetometer.With the 421.7 nm laser pumping atoms from 5S1/2 to 6P1/2, 1366.9 nm transition from 6S1/2 to 5P3/2 can be used as a clock transition of Rb four levels for an atomic active optical clock. An active optical clock is a new conception of the atomic clock and has the potential to improve the stabil- ity of the best atomic clocks by about two orders of magnitude. Another application of the elec- trodeless discharge Rb vapor lamp is the Rb Faraday anomalous-dispersion optical filter （FADOF） （e.g., 776 nm] and 1529 nm spectroscopy）, in which the electrodeless discharge Rb vapor lamp is more feasible than the one using a laser pumped Rb vapor cell in some cases, since many excited states are populated enough for aimed FADOF transition. Although the rich spectra of Rb have many applications, so far no detailed investigations or applications have been achieved in 728.0nm transition. To the best of our knowledge, the Rb 728.0 nm spectral data are currently only from the fluorescence by Beacham arc spectrum of rubidium early in 1959.     

Cs 728 nm Laser Spectroscopy and Faraday Atomic Filter

The laser spectroscopy of alkali-metal vapor is widely used in a number of applications, such as the Faraday anomalous dispersion optical fil- ter （FADOF）, the active optical clock, and wavelength references.Is＇ The Cs electrodeless dis- charge vapor lamp has rich spectra, including 455 nm, 459 nm, 728 nm, 852 nm, 1359 nm, and 1470 nm. The 852 nm laser pumping atoms from 6S1/2 to 6P3/2 have been used in FADOF.The 1359nm wave- length transited from 7S1/2 to 6P1/2 of Cs atoms can be used in the field of active optical clocks. The concept of active optical clocks has been proposed since 2005. Due to its good performance in sta- bility, the active optical clock has been extensively in- vestigated theoretically and experimentally in recent years, such as the two-level active optical clock, and three-level active optical clock. When considering the performance of the active optical clock, we hope to reduce the second-order Doppler shift in thermal atomic beam and the light shift induced by the pump- ing laser. To solve this issue, our group has recently proposed a four-level active optical clock, such as K 1252.2nm, Cs 1469nm, Rb 1366.9nm and Rb 728 nm. Moreover, the Rb 728 nm four-level quantum system has potentially a better performance than three long wavelength ones of Rb.     

基于表面等离子激元的超薄金属减色滤波器的研究

基于表面等离子激元的新型超薄金属减色滤波器具有可靠、易制备、高透射率等诸多优点.本文对银、铜、铝、镍等不同金属材料的超薄一维光栅减色滤波器进行了系统研究.仿真获得了透射光谱,理论计算了对应透射光谱的色品坐标,并推导出了银、铜、铝三种材料透射率最低点波长与膜厚、周期关系的经验公式.仿真研究发现:除了镍的选波性较差外,银、铜、铝均表现出较好的、不同的滤波特性,其中银的滤波范围较广,而铜、铝则分别在长、短波段表现出较好的滤波性能.为了验证仿真结果,利用磁控溅射技术和聚焦离子束刻蚀技术进行了三种材料的一维光栅减色滤波器的制备实验,并在显微镜下观察滤波器的颜色效应,结果与理论仿真相符合.研究结果表明:不同金属材料在相同微结构下的颜色效应存在较大差异,可根据实际滤波需要,选择材料和微结构参数来获得最佳性价比的滤波器.