排序方式: 共有105条查询结果,搜索用时 265 毫秒
91.
大型高功率激光驱动装置中,激光能量密度及系统运行速度主要受终端光学元件损伤增长的限制。为高效、精确地检测元件的损伤状态,提出了一种基于局部信噪比的自适应差异窗过滤算法。该算法通过设计一种作用在像素点上的窗函数,以关联邻域点的像素值强弱完成目标点或背景点的判断,从而完成种子图像的阈值化,最后通过对种子图像区域生长完成损伤分割。为验证算法的有效性,搭建了在线检测模拟平台以获取损伤样品图像,并使用该算法对图像进行处理。结果表明:对直径50μm以上的损伤点,算法的平均识别率在99%以上,达到了高功率激光驱动系统对微小损伤检测的精度要求。因其不需要依据经验设定种子图像的阈值,与现有局部信噪比算法相比具有更高的自动化程度。 相似文献
92.
高功率激光系统中的小尺度自聚焦研究 总被引:1,自引:0,他引:1
概述了高功率激光系统中小尺度自聚焦产生的机理及相应的评价标准和分析方法,重点对激光经过钕玻璃介质和频率转换晶体的小尺度自聚焦情况进行了分析和讨论,同时介绍了两种测量小尺度调制增长的方法。针对高功率激光系统,阐述了抑制小尺度自聚焦的几种方法,提出通过控制小尺度调制增量,减少高功率激光的非线性效应对光学元件损伤的方案。指出了聚变级高功率激光技术中非线性效应研究的发展趋势。 相似文献
93.
为了解决读出过程中全息数据的擦除问题,研究了新型双掺杂LiNbOa:Fe:Ru晶体的全息读出特性。分析了双中心和单中心记录方案光栅的读出特性,并联立双中心物质方程和耦合波方程进行了模拟计算。结果表明,双中心记录所得到的饱和全息的读出时间常数远低于LiNbO2:Fe:Mn晶体的读出时间常数;单色光记录可以实现有效的全息,且其读出时间常数远大于记录时间常数,表现为准态非挥发读出。分析表明,这可能由于Ru的能级比Mn更靠近Fe,更易被红光激发,从而使得双中心记录所得饱和光栅的存贮持久性降低;单色光记录中红光能够同时充当记录光和抽运光,记录过程中红光能够在Fe上记录光栅并将其转移到Ru上,而在读出过程中则由于Ru能级较深,擦除缓慢。 相似文献
94.
The photorefractive sensitivity and the effective electron transport length in two-centre holographic recording
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In this paper the photorefractive sensitivity defined for single-centre holographic
recording is modified to adapt two-centre holographic recording. Based on the time
analytic solution of Kukhtarev equations for doubly doped crystals, the analytical
expression of photorefractive sensitivity is given. For comparison with
single-centre holographic recording and summing the electron competition effects
between the deeper and shallower traps, an effective electron transport length is
proposed, which varies with the intensity ratios of recording light to sensitive
light. According to analyses in this paper, the lower photorefractive sensitivity
in two-centre holographic recording is mainly due to the lower concentration of
unionized dopants in the shallower centre and the lower effective electron
transport length. 相似文献
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97.
Material optimization for low scattering noise during nonvolatile holographic recording in doubly doped LiNbO3 crystals 总被引:3,自引:0,他引:3
Scattering noises in four kinds of lithium niobate crystals with the same double doping system, which are LiNbO3:Fe:Mn, LiNbOs:Ce:Mn, LiNbOs:Ce:Cu, and LiNbOs:Fe:Cu, are observed and compared experimentally. The results show that nonvolatile holographic recording can effectively suppress scattering noise, which mainly depends on recombination coefficients of both the shallower centers and the deeper centers. The small recombination coefficients of the shallower centers and the large recombination coefficients of the deeper centers benefit the amplification of the signal gratings and the suppression of the noise gratings.In addition, the initial seed scattering also impacts the recorded scattering noise, and the little seed scattering results in low scattering noise. The theoretical simulations are performed for confirmation. Among the four kinds of doubly doped crystals, in LiNbOs:Ce:Cu the performances of nonvolatile recording are the best with low scattering noise and high diffraction efficiency. 相似文献
98.
局域体全息光栅的衍射特性 总被引:7,自引:5,他引:2
基于三维耦合波理论,研究了两束有限宽度的任意偏振平面波干涉产生的局域体全息光栅的衍射问题。以单位均匀振幅的任意偏振平面波为例,给出了透射波和衍射波振幅的主分量和交叉分量的解析表达式,讨论了记录过程和再现过程中入射的参考光波的偏振角对透射波和衍射波振幅的影响。计算结果表明,记录过程中的偏振角越小,形成的光栅内的耦合越强,衍射效率越高,但光束质量越差;再现过程中不同的偏振角,由于入射波和衍射波的电矢量的不同方向的耦合强弱不同,透射波和衍射波振幅的主分量和交叉分量的振幅变化行为不同。 相似文献
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100.
远距离激光成像雷达进展 总被引:1,自引:0,他引:1
远距离激光成像雷达在军事侦察和空间监视等领域应用广泛.介绍了几种不同类型远距离激光成像雷达的基本原理,给出几种不同类型的远距离激光成像雷达,并指出了激光成像雷达的发展趋势. 相似文献