Multi-reference lens-less Fourier-transform holography with a Greek-ladder sieve array

Lens-less Fourier-transform holography has been actively studied because of its simple optical structure and its single-shot recording.However,a low-contrast interferogram between the reference and object waves limits its signal to noise ratio.Here,multi-reference lens-less Fourier-transform holography with a Greek-ladder sieve array is proposed in the experiment and demonstrated effectively to improve the signal to noise ratio.The key technique in our proposed method is a Greek-ladder sieve array,which acts as not only a wave-front modulator but also a beam splitter.With advantages of the common path,single shot,and no need for a lens,this system has enormous potential in imaging and especially in extreme ultraviolet and soft X-ray holography.     

基于遗传算法的指纹图像分割算法

在指纹技术中,指纹图像分割是图像处理中关键的一步。将遗传算法用于计算指纹图像分割阈值,采用染色体编码的方法并利用赌轮法产生初始化种群,通过选择算子、交叉算子和变异算子的方法实现分割。该方法表明利用遗传算法所得到的阈值进行分割处理能取得较好的效果。     

Copyright protection in digital museum based on digital holography and discrete wavelet transform

A new method to protect the copyright of digital museum based on digital holography is proposed. The Fresnel hologram of watermark image is embedded in the object to be protected through discrete wavelet transform （DWT）. After the watermark detection, the copyright information appears in the reconstructed hologram. With the higher redundancy feature in the hologram, the proposed technique can actually survive several kinds of image processing. Experimental results prove that the presented method has good robustness in image protection.     

神光Ⅱ终端光学组件的频率变换逆问题研究

在激光惯性约束核聚变(ICF)精确打靶中,对激光束变换、整形和控制要求苛刻,通过数字在线操控技术能够在线实现激光系统的自动校准,而频率变换是数字在线操控技术中的关键一环。在不进行逼近迭代计算的情况下,基于可逆的傅里叶变换和龙格-库塔算法,对神光II终端靶场系统中负单轴晶体KDP的"I+II"类频率变换的逆问题进行了探讨和相应的算法研究,并给出了对应的模拟计算结果。最后,与神光装置运行的实验数据进行比对,验证了频率变换逆问题算法的正确性和稳定性。     

双焦点光子筛聚焦特性的精细测量

利用数字全息测量方法结合变采样间距的衍射传输算法实现双焦点光子筛器件焦距及焦斑的同时精细测量.给出了双焦点光子筛器件及其理论焦斑分布,采用双曝光的离轴全息方法得到了CCD接收面处光场的复振幅分布,基于此光场通过变采样间距的衍射传输算法获得具有较高分辨率的双焦点光子筛的聚焦场特征,与CCD直接测量结果相比,焦斑分辨率提高了10倍,双焦点光子筛的焦距等于自动对焦算法及强度最大值扫描方式分别求得的两段距离之和.实验结果表明测得的双焦距与设计焦距偏差分别为0.53%和0.37%,得到的两个焦斑半值全宽与设计值相比,其偏差分别为2.86%和1.86%.本文提出的测量方法除了应用于光子筛类器件的性能检测以外,还能够广泛应用于其它类衍射透镜聚焦特性的测量与性能分析.     

模拟退火算法优化设计钕玻璃放大器氙灯抽运

氙灯提供的有效抽运能量决定了钕玻璃中反转粒子的数目。针对氙灯供能的要求,建立了氙灯放电回路与氙灯辐射数值模型。将数值模拟结果与实验结果进行了比对,提出了利用模拟退火算法求解最优抽运状态的电路参数的方法,并模拟计算不同电路参数下氙灯的工作状态。定义了两个更实用的评价参数:有效辐射效率和有效输出光谱效率,用于筛选最佳的抽运能量和进灯功率。计算结果表明,在氙灯参数与工作电压一定的条件下,通过利用模拟退火算法可以快速优化放电回路中的电容、电感参数,以选择最佳的进灯能量,避免抽运带内有效能量份额因光谱蓝移而降低,同时可保证氙灯的使用寿命。     

Focusing contribution of individual pinholes of a photon sieve:dependence on the order of local ring of underlying traditional Fresnel zone plate

<正>A photon sieve can be composed of a large number of circular pinholes.Each circular pinhole has a contribution to the focusing.For the case of point-to-point imaging,the focusing contribution of an individual circular pinhole can be analytically given.We investigate the dependence of the focusing contribution on the order m of local ring of underlying traditional Fresnel zone plate.In particular,we find that the focusing contribution is simply inversely proportional to the order m.We also present an intuitive explanation. These results are helpful for better understanding of the focusing property of photon sieves.     

卢卡斯光子筛的聚焦特性研究

介绍了一种基于卢卡斯数编码设计的轴上四焦点光子筛,其各焦距分布与黄金分割比密切相关.实验上利用相移数字全息验证了设计器件具有轴上四焦点聚焦特性,测量结果表明:轴向焦距和横向焦斑光强分布与理论设计值一致.该振幅型光子筛具有体积小、重量轻、易加工等优点,可应用于X波段显微和生物细胞阵列成像等领域.     

高功率激光多程放大器的三维反演方法

针对高功率激光多程放大的三维反演问题,提出了基于修正增益迭代算法结合输入输出积分能量曲线法和基于修正输入脉冲的正向迭代算法。利用这两种方法对有增益分布的四程放大进行数值模拟验证,计算结果表明这两种迭代算法都是有效可行的,都可得到输入脉冲时空分离的三维强度分布。计算所得输出脉冲与需求值基本相同,输出能量的相对偏差小于10~(-7),第一种方法功率波形的相对偏差小于1%,第二种方法功率波形的相对偏差小于10~(-6),很好地解决了由放大饱和效应引起的时空演化畸变。第一种方法主要依靠正逆模型的自洽性,相对直观;第二种迭代算法引入反馈因子,所得结果的精度较高、拓展性强。     

ON THE DECAY AND SCATTERING FOR THE KLEIN-GORDON-HARTREE EQUATION WITH RADIAL DATA

In this paper,we study the decay estimate and scattering theory for the Klein-Gordon-Hartree equation with radial data in space dimension d≥3.By means of a compactness strategy and two Morawetz-type estimates which come from the linear and nonlinear parts of the equation,respectively,we obtain the corresponding theory for energy subcritical and critical cases.The exponent range of the decay estimates is extended to 0<γ≤4 and γ相似文献