共查询到19条相似文献,搜索用时 234 毫秒
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据观测,来自角反射器的激光回波的角闪烁因大气湍流而超过了预计值。本文介绍观测情况并对可能的机理作了理论分析。实验时,采用了一台波长1.06微米脉冲式激光器来照射角反射器。观测结果,激光回波的角闪烁比基准信标大8倍。理论分析中假定照射激光光束存在相位起伏。文中推导出了闪烁角作为相位起伏参数函数的关系式。 相似文献
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介绍了后向散射回波与信标光到达角起伏的原理性比对实验.该实验通过对比的方法验证后向散射的到达角起伏是否可以反映大气湍流强度.实验结果验证了后向散射的到达角起伏可以反映大气湍流强度.并且分析了对比参数. 相似文献
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一、引言 激光束在洁净大气中传播时,由于湍流的影响,光束波阵面到达角将作随机起伏,光束整体将作随机抖动。这些湍流效应严重影响激光大气通信和大气参数的光学法探测,所以人们对此作了大量研究。但是,对激光束在雨和湍流同时存在时传输的到达角起伏和湍流大气中双频光束抖动相关函数研究很少.而这些问题在实际工程应用中常涉及到。 相似文献
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文中介绍了激光信号通过随机大气信道时,大气湍流效应造成了光束抖动、强度起伏,光束扩展和像点抖动等现象。对强度起伏、光束漂移及扩展和相位起伏与到达角起伏进行了理论分析,并在理论分析的基础上设计了实验研究方案,最后得出了相应的实验结果。 相似文献
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本文应用“马尔柯夫近似”和光波复振幅正态分布近似,求得了同时也适用于强起伏区的束状波到达角起伏方差公式和聚焦、准直光束在弱起伏区传播时的到达角起伏方差解析式。 相似文献
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狭激光束运动所致到达角起伏概率和光强起伏统计 总被引:1,自引:0,他引:1
运用到达角起伏的马尔柯夫近似和湍流大气中传输光束的几何光学近似,导出了满足奥伦斯坦-乌伦贝克过程的到达角起伏概率密度的福克-普朗克方程,得到了与传输路程相关的到达角起伏Rician分布概率密度函数,同时讨论了狭激光束到达角起伏导致的光强起伏统计问题。 相似文献
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A novel element for collimating LED light is designed based on non-imaging optics. It is composed of a refraction lens and a reflector. The upper surface of the lens is freeform and calculated by geometrical optics and iterative process. The lens makes the rays in the range of 0°-45°from the optical axis collimated. The rays in the range of 45°-90°from the optical axis are collimated by the reflector. The inner surface of the reflector is parabolic with its focus located in the LED chip. The designed element is applicable to LED source of any emitting type. For a certain application, the simulation results of the designed element in Tracepro show that it has a very compact structure and good collimating performance. Just investigating the loss in the lens surfaces, this element has high light output efficiency of nearly 99%. Most lighting area radii are no more than 20 mm when the illuminated plane is 5 m away from the LED source. 相似文献
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高功率二极管激光器面阵四通抽运耦合系统 总被引:3,自引:3,他引:0
高功率二极管激光器面阵连续抽运1.1mmNd:YAG薄片,采用非球面柱透镜来准直二极管激光器线阵的快轴方向,然后用两个正交的柱透镜分别对快慢轴光进行成像,在薄片上形成10mm×7mm的抽运光斑。用球面反射镜将薄片未吸收的抽运光再一次通过Nd:YAG薄片,从而达到高的吸收效率,抽运光束在薄片上快慢轴方向上的束参数积分别为640mm·mrad和540mm·mrad。用CCD测得抽运光在薄片上的光强分布较均匀,面阵经非球面柱透镜和两个柱透镜后在10mm×7mm内的耦合效率为80.5%。 相似文献
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Results are presented of scintillation spectra, measured at 54.5GHz on a 4.1 km line of sight path, when the variance of the water vapour pressure fluctuations (σe 2) is very much greater than the variance of the temperature fluctuations (σT 2). The effect of σe 2 under these conditions is established both through the experimental results and the theoretical considerations which are also presented. 相似文献
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On Earth-space paths, based on ITU-R C n 2 (h) model, by means of a modification of the Rytov method that incorporates an amplitude spatial frequency filter function under strong fluctuation conditions, considering atmospheric turbulence inner-scale, an expression is developed for the scintillation index of a visible or a near and middle infrared laser beam wave that is valid under moderate to strong irradiance fluctuations. The quantitative analyses of scintillation index are done by this analytic model for laser Gaussian collimated beam wave at visible or near and middle infrared wave band. The results agree with theoretic analysis scintillation. This scintillation model can be converted into a Gaussian beam wave model with finite inner-scale on horizontal sight paths of invariable C n 2. 相似文献
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Spherical reflector systems can achieve pattern scanning without rotation of the main reflector through the use of multiple subreflectors that can move. Also, two subreflectors can be shaped to correct for spherical aberration and to control the aperture distribution on the spherical main reflector. In a previous paper (see ibid., vol.41, p.778, no.6, 1993) we introduced a method that offers both aperture phase and intensity control and scans the main beam without an accompanying movement of the illuminated area over main reflector. The method can overcome the poor aperture utilization problem common in spherical reflector antenna systems; however, it requires motion of the entire subreflector system, including the feed, during scan. In this paper we discuss a method that does not require motion of the subreflector system during scan. This method employs a flat mirror that creates a virtual image of the subreflector system. The motion of the subreflector system in the previous design is replaced by the motion of the virtual image that is controlled by the motion of the flat mirror. The new design offers simplified mechanical motion, while maintaining beam efficiency performance comparable to that of traditional spherical tri-reflector scanning antennas, but with some sacrifice in aperture efficiency and cross-polarization performance 相似文献
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光在45°入射时,通过置于空气中的介质表面的反射强度,可用偏振的数学描述来表达.结合光在两透明电介质分界面上的反射时的菲涅耳反射系数的复振幅rs、rp与折射介质对入射介质的介电常数ε之问有一个数学表达式:(rs-rp)/(1-rs·rp)(1-ε)/(1+ε),即可推导出介质的复数折射率表达式为:N=(rs2+1)/(rs+1)2. 相似文献
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The split-radix algorithm (SR) is a highly efficient version of the successive doubling method (SD). Its application to the
Fourier transform results in an algorithm that brings together the advantages of the radix 2 and radix 4 algorithms. In this
work we present the generalization of the method that leads to the SR algorithm in the FFT and the implementation of a constant
geometry (CG) version of it. In particular, we develop a CG algorithm of the successive doubling method that factorizes a
sequence of lengthN intop sequences of lengthN/r and into (r−p)r of lengthN/r
2(r≥2, 0<p<r). After this, the method is generalized for its application to SRr, r
2,...r
u
algorithms, that is, to those based on the factorization of a sequence of lengthN intop
1 subsequences of lengthN/r, p
2
r of lengthN/r
2,...,p
u
r
u−1 of lengthN/r
u
(p
1+p
2+...+p
u
=r). The results are applied to the implementation of a pipeline with identical stages and to a processor column.
This work was supported by the Ministry of Education and Science (CICYT) of Spain under project TIC-92-0942-C03. 相似文献