平面近场声全息重建结果不准确性问题的研究

平面近场声全息作为一种有效的声场分析方法被广泛用于声场分析和振动体的振动模态及其辐射声场的研究。在介绍了平面近场声全息理论的基础上,指出了利用该方法进行声场重建时存在质点振动速度和声强重建不准确的问题,并从理论分析和模拟计算两个方面给予了证明,在此基础上进一步分析了该方法的应用局限性。     

Phasing of lysozyme using one－wavelength anomalous scattering of sulphur atoms through the combination of direct methods and density modification

A new method of combining one-wavelength anomalous scattering (OAS) phasing and density modification has been described, in which the improved phases from density modification axe re-introduced into OAS phasing. In this way, the phases could be improved iteratively until convergence. The OAS phasing method is based on the previously established sign-probability formula, which breaks the phase ambiguity in the OAS phasing. The implementation of this method has been available in CCP4 as OASIS. This method, although based on direct-methods, could also incorporate known phases and figures of merit into its sign-probability formula. In the implementation of OASIS, the known phases axe from the positions of the anomalous scatters. In the current method, the known phases are from the density modification. The current method was tested on phasing a lysozyme crystal using anomalous scattering of sulphur atoms with diffraction data collected on an in-house x-ray source. The resulting map was well connected for the backbone atoms and clearly traceable, with an average map correlation coefficient of 0.6622 for the backbone atoms.     

多程放大系统光学元件静态波前畸变研究

通过研究光学元件静态波前畸变对多程放大系统光传输的影响,给出了满足聚焦光斑要求的均方根梯度值以及光学元件加工误差的最大允容值。加工误差的峰谷值不超过λ/3、均方根值不超过0.079λ,相位梯度的峰谷值不超过0.033λ/cm、相位梯度均方根不超过0.007λ/cm。通过光传输模拟程序校验了波前畸变的相干叠加和非相干叠加规律。     

共轭读出法消除光致变色材料全息记录中的相位畸变

采用有机光致变色材料-吲哚俘精酰胺/PMMA薄膜作为可擦写全息记录介质,建立了一种能消除全息光存储中相位畸变的光路.此光路采用参考光的相位共轭光再现全息图,能有效消除物光路中由于光学元件失调和记录材料缺陷引起的相位畸变,是全息光存储中提高再现像像质的一种有用光路.     

一种水声环境下易于硬件实现的盲波束形成方法研究

针对水声环境和水声信号的特点,提出了一种基于高阶累积量的神经网络盲波束形成算法。该方法把高阶累积量可消除高斯噪声干扰这一特性和神经网络可并行计算的结构优势有机地结合起来,不但有效地避免了矩阵求逆运算,而且易于用硬件实时实现盲最优波束形成。仿真实验验证了该算法的有效性和正确性。     

强激光系统光学元件波前相位梯度分析

 介绍了在高功率固体激光系统中用于评价光学元件对光束聚焦特性影响的参数——波前相位梯度及其检测原理和计算方法,并与常用的光学元件评价参数P V值、RMS值以及新引入的评价方式——PSD进行了比较。得到了高功率激光系统中几种典型光学元件的相位梯度分析结果,结果表明利用相位梯度分析方法能够有效的对光学元件的加工质量进行评价。     

相位不连续点对自适应光学的影响

分析了激光在湍流大气中传输时,若光束波前中出现相位不连续点,自适应光学校正能力降低的原因,通过数值模拟计算了当光束波前中出现相位不连续点时对自适应光学校正的影响,表明在传输过程中出现不连续点的情况下,为了提高自适应光学的校正能力,必须要考虑不连续相位的影响。