The method of combined inspection

For costly and/or destructive inspections for a complex population, the sum of observations, the test statistic in common use, is shown to be inefficient in risk control. For the complex population consisting of Bernoulli distributions, the method of combined inspection is proposed in this paper, Evaluation based on examples and simulation results is conducted according to the method of limited classification. It is concluded that the new method is efficient and applicable.     

液晶自适应光学的研究进展

概述了中科院长春光学精密机械与物理研究所(长春光机所)在液晶自适应光学方面的研究进展。针对液晶自适应光学技术存在的能量利用率低和校正频率慢的两大国际难题,液晶自适应光学研究组采取了一系列有效措施,不但攻克了能量利用率低的难题,且在校正频率方面也取得了质的飞跃。目前,系统能量利用率已从最初的5%提高到85%,基本和变形镜自适应光学系统的能量利用率相当;校正频率也从5 Hz提高到140 Hz,接近了校正大气湍流的实用化水平。利用该研究成果,分别研制了针对中科院国家天文台2.16 m望远镜和长春光机所1.2 m望远镜的液晶自适应光学系统并对恒星进行了有效校正,使1.2 m望远镜对恒星的分辨能力提高至约3倍衍射极限。     

用于开环液晶自适应光学系统的模式预测技术研究

时间延迟误差是液晶自适应光学系统的一个最主要的误差源. 本文提出了一种利用智能模式预测-----迭代最小二乘(RLS)模式预测算法来克服其对成像分辨率的影响. 首先, 介绍了具有RLS模式预测能力的开环液晶自适应光学系统的结构和工作原理. 其次, 详细讨论了RLS模式预测算法的实现过程. 再次, 设计和搭建了一套带有液晶湍流模拟器的开环液晶自适应光学系统, 对RLS模式预测算法的预测效果进行了分析, 并和直接开环校正做了比较. 分析结果表明: 当系统处于中等强度湍流条件(大气相干长度r₀=6 cm, Greenwood频率f_G=35 Hz)和只有时间延迟误差情况下, 经过RLS预测后, 残差波面的RMS值由直接校正的0.26波长(1波长=785 nm)降低到了0.15波长, 校正效果提高了42%. 最后, 对预测前后自适应光学系统的成像效果进行了对比试验. 实验结果显示, 经过预测以后, 系统的成像分辨率由直接开环校正的25.4 cycles/mm提高到了32.0 cycles/mm, 成像分辨率提高了26%, 达到了0.9倍的衍射极限分辨率. 因此, RLS模式预测技术可以有效的提高开环液晶自适应系统的成像分辨率.     

大口径望远镜波像差的外场检验方法

为在外场环境下对大口径望远镜进行系统波像差的检验,研制了一套具有高探测能力的Shack-Hartmann波前传感器.利用恒星作为光源,对口径1 m、焦距11 m的大口径望远镜进行了波像差检验实验,测量结果为系统波像差在0.39λ~ 0.46λ RMS之间,且随着俯仰角的增加而增大,主要像差形式为3阶0°像散,与星点检验的结果一致.     

Reanalysis of optical-axis perturbation in nonplanar ring resonators in ray matrix approach with appropriate coordinate systems

Ray matrix approach with appropriate coordinate systems has been proposed in this paper. It is employed to analyze the optical-axis perturbation in nonplanar ring resonators. The sensitivities of optical-axis decentration (SD) and optical-axis tilt (ST) in nonplanar resonators with 90° and 270° image rotation are discussed in detail in the region of 0 < K < 8, where K is the ratio of the total cavity length to the radius of the curvature mirrors. There are both four singular points in the whole region of 0 < K < 8. On the left of the first singularity, it is found that the longer the mirror radius, the less the optical-axis decentration sensitivity. This is opposite the behavior of planar ring resonators, but the behaviors of optical-axis tilt sensitivity in planar and nonplanar ring resonators are similar. It is worth to note that SD and ST in the nonplanar resonator with certain parameters have the similar singularities. The analysis in this paper is important for the cavity design and alignment of nonplanar ring resonators.     

在随机和倾斜移相下光强归一化的迭代移相算法

由于存在振动和导向误差,干涉仪移相器在移相过程中产生随机的平移误差和倾斜误差,会给测量结果带来影响。因此高精度测量中对环境的稳定性和移相器的性能要求很苛刻。为了降低此种要求,针对随机和倾斜移相下干涉图背景光强和调制度的不均匀会影响移相平面计算的问题,对采集得到的干涉图做归一化处理,并利用迭代最小二乘法对归一化的干涉图做相位求解。迭代过程中,将干涉图分块来求解移相值,并对各移相值做平面拟合得到移相平面。仿真结果表明,该方法消除了背景光强和调制度的不均匀对倾斜系数计算的耦合作用,能够有效补偿倾斜移相误差对面形相位的影响,与其他方法相比,具有收敛速度快、求解精度高的特点。实验结果进一步验证了该方法的有效性。     

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。     

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.     

Studies of transverse chromatic aberration based on individual eye model

Two kinds of individual eye models, with and without involving the angle between visual axis and optical axis, are constructed according to the measurements of the corneal surfaces, the optical axis lengths and wavefront aberrations. The constructed eye models are then used to investigate the properties of the transverse chromatic aberration (TCA) and its influence on visual performance. The statistical distributions of the horizontal TCA, vertical TCA and the absolute magnitude of the TCA over the spectrum from 470 to 650 nm are provided, respectively. The variations of TCA with wavelength as referring to the central wavelength of 555 nm for five subjects are also provided. Then we evaluate the impact of TCA on image performance in comparison with longitudinal chromatic aberration (LCA). It is shown that LCA is more detrimental than foveal TCA in image quality. It is found that, while LCA was corrected well, the foveal TCA is simultaneously corrected. Finally, we investigate the correction of peripheral TCA with an achromatizing element. The correction of peripheral TCA of human eye strongly depends on the location of the achromatizing element, and with the element in front of the eye, the peripheral TCA cannot be corrected.