共查询到19条相似文献,搜索用时 228 毫秒
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对一种基于线性相位反演的新型波前测量方法的基本原理和性能进行了研究。事先对成像光学系统的自身像差进行定标并记录下定标图像。传感器工作时只需测量出有像差时的一幅远场图像与定标图像的差,就可以用线性矩阵相乘方法得到待测像差对应的泽尼克多项式系数。讨论了这种线性相位反演波前测量方法中确定泽尼克模式复原矩阵的方法。以大气湍流畸变波前像差的测量为例,对这种线性相位反演波前测量方法进行了数值仿真研究。结果表明,这种线性相位反演算法具有空间分辨力高、对小像差测量精度高的特点,但测量动态范围有限。这种线性相位反演波前传感器将适用于自适应光学闭环系统。 相似文献
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一种用于光学成像系统的新型液晶相位调制器 总被引:1,自引:0,他引:1
研制出新型平行排列的二维阵列液晶相位调制器(LCPM),利用此相位调制器在Zygo干涉仪上进行了泽尼克(Zernike)多项式的产生和畸变波前调制的实验。能够很好地产生泽尼克多项式的前2~8项面形,用16项泽尼克模式对畸变波前进行了调制,峰谷(PV)值可由调制前的0.831λ减小到调制后的0.444λ,均方根(RMS)由调制前的0.181λ减小到调制后0.066λ,斯特列尔比(Strehl ratio,SR)由调制前的0.257达到调制后的0.844。实验结果表明,在光学成像系统中,利用平行排列的液晶相位调制器,进行波前像差的调制可以使成像质量得到很好的改善。 相似文献
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光学相干层析成像(OCT)的图像质量会受到散斑噪声的影响,限制了OCT在临床诊断中的应用。叠加取平均是一种降噪的常用方法,作为相干噪声,散斑降噪的关键在于降低用于叠加的图像之间的散斑相关度。提出了一种基于纯随机相位板的散斑去相关OCT系统(PSD-OCT)。利用纯随机相位板调制样品光的波前相位以实现散斑去相关,从而为采用叠加取平均降低OCT图像噪声的方法提供低相关数据。成像实验证明了纯随机相位板能够降低散斑相关度,提升叠加图像的散斑信噪比,使得生物样品的精细结构更为清晰明显。与传统OCT的相关叠加相比,PSD-OCT的去相关叠加可以大幅降低散斑噪声从而增强OCT图像的视觉可见性,且无需搭建复杂系统,具有广泛的生物医学成像应用前景。 相似文献
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基于泽尼克多项式进行面形误差拟合的频域分析 总被引:3,自引:3,他引:0
获得泽尼克多项式的频谱信息是正确利用该多项式进行误差拟合的关键。推导出了泽尼克多项式的傅里叶变换公式,在频域中分析了不同阶数该多项式的径向频谱信息和幅角频谱信息,得到了有限项泽尼克多项式能够有效表达面形误差的最大径向空间频率和角频率。基于频域分析理论,利用泽尼克多项式对不同口径局部误差进行了拟合,并利用齐戈(Zygo)干涉仪对带有不同面形误差的光学元件进行了试验分析。结果表明,当误差的径向空间频率或角频率超出泽尼克多项式所能表达的频谱范围时,拟合误差迅速变大。 相似文献
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基于DDE接口技术的计算机辅助装调方法 总被引:1,自引:0,他引:1
根据波前拟合和计算机辅助装调的算法原理,基于动态数据交换(DDE)接口技术和泽尼克多项式拟合技术,采用阻尼最小二乘法,运用MATLAB和ZEMAX联合计算实现了计算机辅助装调。利用DDE接口在ZEMAX和MATLAB之间进行通讯,并用MATLAB编写了能够生成各阶泽尼克圆多项式和环多项式的基底矩阵函数的可视化的计算机辅助装调程序,实现了程序的通用性及易用性。使用该程序对大遮拦比光学系统进行模拟装调,验证了程序的正确性。为了确认泽尼克圆多项式在环域上的相关性对计算机辅助装调结果的影响,分别采用泽尼克圆多项式和环多项式进行模拟装调。模拟结果表明:计算机辅助装调使用这两种泽尼克多项式均可行。 相似文献
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为了解决在数字散斑干涉技术测量时,散斑干涉相位条纹图像中大量噪声对相位解包裹结果和精度产生严重影响的问题,介绍了一种条纹正余弦分解和频域低通滤波结合的方法,实现了散斑干涉相位条纹图的高精度滤波。该方法的基本思路是在对相位图像进行滤波处理前,先将相位图通过正余弦函数进行映射转换成两幅图,分别经过频域滤波,然后再合成为相位图。这种分解频域滤波方法可以在滤波的同时,有效保留相位跳变信息。实验结果表明:与传统的图像降噪方法相比,该方法能够在保留图像“尖峰”信息的基础上,较好地滤除图像中的散斑噪声,方法简单有效,有效解决了传统滤波方法应用在相位条纹图中,相图灰度信息丢失10%~40%的问题。 相似文献
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Mohammad Moradi 《Optical Review》2008,15(2):125-129
The goal of this study was to analyse anisoplanatism of adaptive optics under an inhomogeneous turbulent atmosphere over a
pupil of finite size. By means of a numerical model with layers of turbulence software was proposed by which point spread
function (PSF), optical transfer function (OTF) as well as system isoplanatic angle can be calculated. Atmospheric turbulence
was simulated with the aid of a set of moving random phase screens with arbitrary statistics. Both reference and target are
assumed to be the point light sources. To simulate atmospheric turbulence we applied the concept of a number of moving random
phase screens with Kolmogorov spectrum. In my investigation I used the model of the Shack-Hartmann wave front sensor and the
ideal model of a wave front adaptive mirror that is assumed to reproduce a given number of Zernike polynomials without time
delays. The designed software allows calculation of instantaneous and average values of phase correction errors at different
angles between a reference beacon and target source. Simulations can be made with a broad range of parameters of an adaptive
system and atmospheric turbulence. The system of the model allows changing of the control algorithm of phase correction. Both
common phase conjugation and weighted phase conjugation algorithm have been tested. This program is capable of calculating
the effects of beam diffraction during propagation in the atmosphere. 相似文献
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Heng Chen Zhili Wang Kun Gao Qiyue Hou Dajiang Wang Ziyu Wu 《Journal of synchrotron radiation》2015,22(4):1056-1061
In recent years, increasing attention has been devoted to X‐ray phase contrast imaging, since it can provide high‐contrast images by using phase variations. Among the different existing techniques, Zernike phase contrast microscopy is one of the most popular phase‐sensitive techniques for investigating the fine structure of the sample at high spatial resolution. In X‐ray Zernike phase contrast microscopy, the image contrast is indeed a mixture of absorption and phase contrast. Therefore, this technique just provides qualitative information on the object, which makes the interpretation of the image difficult. In this contribution, an approach is proposed for quantitative phase retrieval in X‐ray Zernike phase contrast microscopy. By shifting the phase of the direct light by π/2 and 3π/2, two images of the same object are measured successively. The phase information of the object can then be quantitatively retrieved by a proper combination of the measured images. Numerical experiments were carried out and the results confirmed the feasibility of the proposed method. It is expected that the proposed method will find widespread applications in biology, materials science and so on. 相似文献
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在考虑时间特性的激光大气湍流数值模拟中,构造满足要求的湍流相位屏对大气湍流的模拟尤为重要,为此提出基于多点预测的相位协方差插值方法产生湍流相位屏,由多个已知点的相位值对新插值点的相位值进行预测,推导出了插值点的预测矩阵及其残余方差的表达式,并对插值后生成的相位屏的空间统计特性进行了验证。数值模拟结果表明:该方法产生的湍流相位屏与大气湍流的统计特性符合得较好,随着用于预测的已知点数的增加,模拟生成的湍流相位屏的精度提高,并可以进行连续插值生成无限长的湍流相位屏。 相似文献
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Since the invention of Zernike phase contrast method in 1930,it has been widely used in optical microscopy and more recently in X-ray microscopy.Considering the image contrast is a mixture of absorption and phase information,we recently have proposed and demonstrated a method for quantitative phase retrieval in Zernike phase contrast X-ray microscopy.In this contribution,we analyze the performance of this method at different photon energies.Intensity images of PMMA samples are simulated at 2.5 keV and 6.2 keV,respectively,and phase retrieval is performed using the proposed method.The results demonstrate that the proposed phase retrieval method is applicable over a wide energy range.For weakly absorbing features,the optimal photon energy is 2.5 keV,from the point of view of image contrast and accuracy of phase retrieval.On the other hand,in the case of strong absorption objects,a higher photon energy is preferred to reduce the error of phase retrieval.These results can be used as guidelines to perform quantitative phase retrieval in Zernike phase contrast X-ray microscopy with the proposed method. 相似文献
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Tatsuro Otaki 《Optical Review》2001,8(4):284-286
A new phase contrast microscopy technique has been developed which achieves halo reduction by applying an apodization to the Zernike phase contrast method. In this technique, a new apodized phase plate is placed at the back focal plane of the objective. This plate consists of a quarter wave phase shift ring conjugated of the illuminating aperture, which has a 25#x0025; transmittance, and a pair of adjacent rings having 50#x0025; transmittance. The developed technique yields the highest resolution images without a bluish hue effect ever achieved in phase contrast microscopy.This paper was originally presented at the 2nd International Conference on Optical Design and Fabrication, ODF2000 which was held on November 15-17, 2000 at the International Conference Center, Tokyo, Waseda University, Japan. 相似文献
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Zernike polynomial decompositions are used for investigating phase distortion induced by atmospheric turbulence in optical systems. Closed-form expression of the Zernike-coefficient variances is derived. The finite size of the receiver aperture is analyzed using the filter function which is also particularly effective in the theoretical analysis of lower-order aberrations like tilt terms and piston-removed phase variance. The outer scale of the non-Kolmogorov turbulence is considered. The result shows that the effect of finite outer scale attenuates low-order Zernike mode of optical distortion and longer outer scale can lead to more energy in the tilt terms. The generalized exponent can only enhance tilt terms and attenuate other Zernike modes of optical distortion. Further, for different outer scale and generalized exponent, the residual phase variance decreases with more modes of phase compensation. 相似文献
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相位恢复法利用光波传输中某一(或某些)截面上的光强分布来传感系统波前,其结构简单,不易受震动及环境干扰,被广泛应用于光学遥感和像差检测等领域.传统相位恢复法采用迭代计算,很难满足实时性要求,且在一定程度上依赖于迭代转换或迭代优化初值.为克服上述问题,本文提出了一种基于卷积神经网络的相位恢复方法,该方法采用基于小波变换的图像融合技术对焦面和离焦面图像进行融合处理,可在不损失图像信息的同时简化卷积神经网络的输入.网络模型训练完成后可依据输入的融合图像直接输出表征波前相位的4-9阶Zernike系数,且波前传感精度均方根(root-mean-square,RMS)可达0.015λ,λ=632.8 nm.研究了噪声、离焦量误差和图像采样分辨率等因素对波前传感精度的影响,验证了该方法对噪声具有一定鲁棒性,相对离焦量误差在7.5%内时,波前传感精度RMS仍可达0.05λ,且随着图像采样分辨率的提升,波前传感精度有所改善,但训练时间成本随之增加.此外,分析了实际应用中,当系统像差阶数与网络训练阶数略有差异时,本方法所能实现的传感精度,并给出了解决方案. 相似文献
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Tatsuro Otaki 《Optical Review》2000,7(2):119-122
A new phase contrast microscopy technique for halo reduction is proposed. This technique is based on an apodization method combined with the Zernike phase contrast method. Although it has been a difficult theoretical problem, the proposed technique achieves halo reduction by considering angles of diffraction and phase differences. The technique utilizes an apodized phase plate consisting of a quarter wave phase shift ring with a 25% transmittance, and a pair of adjacent rings, which have 50% transmittance. This element is placed at the back focal plane of the objective. The result is startling, halo reduced images of phase objects providing enhanced inner details. 相似文献