The study of the effects of higher-order aberrations on human contrast sensitivity with white-light retinal aerial image modulation (AIM)

The impact of higher-order aberrations on contrast sensitivity function (CSF) is calculated using individual white-light retinal aerial image modulation (AIM). Wavefront aberrations of 26 eyes are measured with Hartmann-Shack sensor, and the CSFs in natural light are acquired through a range of 2-48 c/deg. The white-light AIM is computed as the ratio of modulation transfer function (MTF) in white-light to CSF. Through manipulating the higher-order aberrations, the affected CSF is predicted by employing the white-light AIM. We find that coma aberration mainly influences CSF at higher spatial frequency and spherical aberration affects CSF in the whole spatial frequency range non-selectively. Additionally, it is spherical aberration rather than coma that impacts the CSF more substantially. Furthermore, the maximum value of area under CSF (AUCSF) is obtained without full correction of higher-order aberration, which indicates that there is compensatory mechanism among aberrations.     

Effective medium model for flow through beds of porous cylindrical fibres

We have used effective medium model for beds of circular cylindrical porous fibres in order to estimate the overall bed permeability (OBP). It is assumed that a representative circular porous cylindrical fibre is inside a fluid envelope beyond which effective medium is used. Both inside the cylindrical fibre and in the effective medium, Brinkman equation is used, however of different permeabilities and in the fluid envelope Stokes equation is used. The OBP corresponding to the porous fibres is estimated when the flow direction is perpendicular to the axis of the cylindrical fibres as well as parallel to the fibres. This in turn is used to estimate the OBP corresponding to a collection of porous cylindrical fibres that are randomly oriented. We have compared the results with some existing literature.     

基于并行梯度下降算法模拟高功率固体激光装置的相干合成

 多路光的相干合成是高功率固体激光装置的关键技术之一。基于合成模型,对4组tilt/tip-piston镜采用并行梯度算法,通过模拟计算实现了光束间的位相锁定和相干合成。结果表明有限次算法迭代次数内,相干合成时远场焦斑10 μm半径范围内的强度比约为非相干合成时的4倍。基于高频响应驱动器和对应的高速控制算法将有可能实现高功率固体激光装置多路输出光束间的相干合成。     

高分辨率空间光学遥感器波像差的无波前传感器自适应光学校正

高分辨率空间光学遥感器在轨工作时,由于受到各种因素的影响,无法清晰成像,目前多采用自适应光学方法与技术进行校正.传统自适应光学系统体积较大,结构复杂,难以应用于高分辨率空间光学系统的在轨校正.无波前传感器自适应光学系统去除了传统自适应光学中的波前传感器,大大简化了系统结构,具有体积小、易于实现等优势,特别适用于高分辨率...     

基于矢量波像差理论的两反光学系统装调研究

 为了实现对两反光学系统的精密装调,提出一种基于矢量波像差理论和波像差检测技术对失调量精确求解的装调方法。使用矢量波像差理论,将已设计的两反光学系统参数、失调量和失调光学系统的波像差之间建立方程;然后通过干涉测量法得到某一个视场的干涉图,利用条纹分析软件得到表征失调系统三阶彗差和三阶像散的泽尼克项系数,将泽尼克项系数代入方程从而求解出失调量。运用此方法对4 m口径RITCHEY-CHR-TIEN结构的天文望远镜进行模拟装调,最终求解的失调量与引入的失调量结果相互吻合,说明该装调方法正确。     

Focal shift of cylindrical vector axisymmetric Bessel-modulated Gaussian beam with radial variance phase wavefront

Axisymmetric Bessel-modulated Gaussian beam with quadratic radial dependence (QBG beam) has attracted much attention recently. In this paper, the focal shift of the cylindrical vector QBG beam with radial variance phase wavefront is investigated theoretically by vector diffraction theory. Results show that focus shifts considerably by changing the phase parameter C that indicates the radial phase variance speed. Under condition of small beam parameter μ of cylindrical vector QBG beam, there is one focal peak that shifts far away from optical aperture on increasing C. When μ increases, there may occur two focal peaks that also shift remarkably on increasing C. And it was found that the dependence of focal shift distance on increasing phase parameter is linear. Phase parameter adjusts the focal shift distance, while, polarization angle does not affect focal shift obviously.     

Large‐surface‐area diamond (111) crystal plates for applications in high‐heat‐load wavefront‐preserving X‐ray crystal optics

Fabrication and results of high‐resolution X‐ray topography characterization of diamond single‐crystal plates with large surface area (10 mm × 10 mm) and (111) crystal surface orientation for applications in high‐heat‐load X‐ray crystal optics are reported. The plates were fabricated by laser‐cutting of the (111) facets of diamond crystals grown using high‐pressure high‐temperature methods. The intrinsic crystal quality of a selected 3 mm × 7 mm crystal region of one of the studied samples was found to be suitable for applications in wavefront‐preserving high‐heat‐load crystal optics. Wavefront characterization was performed using sequential X‐ray diffraction topography in the pseudo plane wave configuration and data analysis using rocking‐curve topography. The variations of the rocking‐curve width and peak position measured with a spatial resolution of 13 µm × 13 µm over the selected region were found to be less than 1 µrad.     

一种优化波前编码系统相位板参数的新方法

根据波前编码系统的设计理论,在兼顾图像恢复能力的基础上,提出利用不同离焦距离的点扩散函数与焦面处的点扩散函数之间的希尔伯特空间角作为成像特性一致性的评价函数,结合遗传算法,对扩大景深的波前编码成像系统的相位板参数进行优化。分别在空间域和频率域上分析应用波前编码技术前后光学系统的成像特性,并利用最小二乘数字滤波器对中间模糊图像进行复原。仿真实验结果表明:在三次相位板上应用此方法获得的最佳相位板参数使波前编码系统焦深扩展了10倍。     

基于阈值式小波变换的波前重构算法

 针对传统的波前重构器计算效率低、稳态误差大的问题,提出了阈值式波基多分辨力波前重构算法,采用4维波基作为标准正交基,将波前相位畸变投射到4维波基上,使伪逆矩阵变为稀疏矩阵,有效地减少了计算量,并采用阈值法去除波前重构矩阵算子中对精度影响较小的高分辨力波基系数,进一步增加了矩阵的稀疏程度,提高了运算效率,并与传统的最小二乘法、Zernike模式法和迭代法进行了计算量和均方根误差的比较,仿真结果表明该算法无论在计算速度和收敛精度上均优于其它算法。     

自适应光学系统中波前传感器噪声的闭环传递特性

 分析了Shack-Hartmann 波前传感器（S-H WFS）在实际大气条件下,大气湍流波前相位的探测误差在自适应光学系统（AOS）中的传递过程以及最后的控制残余方差,导出了定量分析的数学模型,并给出了分析结果。结果表明,当S-H WFS用于微弱信标光大气湍流的探测时,自适应光学系统中的控制斜率残余误差中除了前人分析[1]的误差外还包含一项由天空背景光斑质心位置引起的常数误差值,并且系统的有效控制带宽会因信标探测对比度的下降而减小,这将大大降低AOS的校正能力。分析结果还表明信标光越弱,对S-H WFS的标定光学系统的像差要求越高。