共查询到20条相似文献,搜索用时 46 毫秒
1.
Francisco Jose Torcal-Milla Luis Miguel Sanchez-Brea Eusebio Bernabeu 《Optics Communications》2008,281(23):5647-5652
Steel tape gratings are used in different metrology applications. As the period of these gratings was large (around 100μm,), its analytical study has been performed, up to date, using a geometrical approach. Nowadays, steel tape gratings can be manufactured with lower periods, around 20-40 μm, and diffractive effects must be taken into account. Also, due to the roughness of the surface, statistical techniques need to be considered to analyze their behavior. In this work, an analysis of the pseudo-imaging formation in a double grating system including one steel tape grating is performed. In particular Moiré and Lau configurations are analyzed. We have found that roughness significantly affects to Moiré configuration. However, its effect is negligible in Lau configuration. Generalized grating imaging configuration is also studied in depth. It is shown that roughness does not affect to the contrast of pseudoimages, but it modifies their depth of focus. 相似文献
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The Lau effect is investigated as a result of the propagation of partially coherent light. It is found that the fringe structure is dependent on the relationship between the grating separation and the periodicity of the complex degree of spatial coherence in the plane of the second grating. This provides a simple and elegant means of interpreting and extending the Lau effect. 相似文献
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The use of a grating in the form of modulation of birefringence in a BSO crystal in a novel Lau interferometer set-up is proposed. The system behaves as a conventional Lau interferometer implemented by using two amplitude gratings. Moreover, it permits control of the visibility and provides a contrast inversion of the interferometric fringes by rotating a polarizer. Two alternative experimental arrangements with similar performance are presented. A theoretical approach is outlined and the predicted behavior is confirmed by results obtained under different experimental conditions. 相似文献
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本文用部份相干的观点提出并研究了三个独立光栅串联排列系统的干涉效应。用模糊函数导出了干涉条纹光强分布为三个光栅等效函数的联合卷积-相关积分。给出了条纹存在的光栅间距离和周期比条件。随光源光栅狭缝宽度的变化相应产生相干的Talbot效应、部份相干效应和非相干的Lau效应。部份相干条纹的波形随光栅的平移而变化。最后给出了实验验证。
关键词: 相似文献
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本文用离轴傅里叶变换系统的模型和菲涅耳衍射理论分析了衍射受限下的离焦相关器的系统特性,证明是第一模板和第二模板衍射像之间的强度相关积分。推导了衍射相关器作为测量相位物体的干涉仪的一般理论,这时要求编码板函数能衍射自成像并且相关函数为周期性函数。讨论了平行光栅作为编码板时的干涉仪的横向剪切干涉特性,给出了实验结果。本文还证明了衍射相关器是推广到任何平面物体在任何观察距离上的Lau效应装置。衍射相关干涉仪产生Lau干涉条纹,并且是直接应用Lau效应的干涉仪。
关键词: 相似文献
7.
ANALYSIS OF THE GENERAL EFFECTS IN DOUBLE-GRATING DIFFRACTION-INTERFERENCE SYSTEM 总被引:2,自引:0,他引:2 下载免费PDF全文
Based on the ambiguity function, the optical phenomena of the double-gearing diffraction-interference system are analysed with partially coherent illumination. Different patterns are observed on the observation plane when the optical elements are placed in their proper positions. Detailed discussions on the two extremes of coherence are given. Conclusions could be obtained about the Lau effect, the generalized Lau effect, the incoherent grating-lens imaging, the Talbot effect, the joint-Talbot effect and the generalized joint-Talbot effect. Some special cases are also verified by experiments. 相似文献
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基于部分相干理论中交叉谱密度函数的概念研究了平面周期物体的Lan效应文章导出了平面物体Lau像光强分布式,求得了平面周期物体的Lau像光强分布及其Lau成像条件,并进行了实验验证,给出了实验结果. 相似文献
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The Lau effect is an interference phenomenon involving two gratings and incoherent illumination. Here the Lau effect is described in terms of the OTF theory. It is shown that this analysis is equivalent to that given in terms of coherence theory. 相似文献
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模糊函数和任何光学系统中的Talbot-Lau效应 总被引:3,自引:2,他引:1
本文用模糊函数处理了光栅的Talbot和Lau效应,并推广到任何光学系统中。得到了十分简洁的通用表达式,它能够直接描述干涉条纹的空间分布,并只与系统的传递矩阵有关。同时也讨论了Talbot和Lau效应中的相位关系。 相似文献
12.
Sumitra Singh 《Optik》2014
New filtering scheme is investigated and implemented on Lau interferometric fringes to enhance the signal-to-noise ratio (SNR) in the Lau interferograms. Towards this, the applicability of Haar, Daubechies and Symlet wavelet based filtering schemes have been tested. Of these schemes, the Symlet based filtering scheme gives the best results in terms of improved signal to noise ratio and speckle index. This scheme is then used to analyse Lau interferograms recorded in the experimental arrangement for focal length measurement. The processed interferograms yield improved accuracy and precision of measurement. 相似文献
13.
G. R. Lokshin A. V. Uchenov M. A. Éntin V. E. Belonuchkin N. I. Eskin 《Optics and Spectroscopy》2000,89(2):312-317
The locations of self-reproduction planes in the Talbot effect and the distance between coherence peaks in the Lau effect are functions of the radiation wavelength. This fact can be used to develop new methods for spectral investigations. Below, we estimate the spectral selectivity of Talbot and Lau effects and compare it with the resolving power of traditional spectrographs with diffraction gratings. 相似文献
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借助模糊函数理论分析了空间周期相干光照明产生的自成像现象及Lau效应。理论分析结果表明:当照明光源满足一定条件时,会出现自成像现象及Lau效应。根据分析结果讨论了这些现象的可能应用。 相似文献
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In this paper, the surface profile of objects is determined by using a grating projection system. The method is based on the concept of self-imaging, namely, the Lau effect. Periodic fringe patterns are generated from the projection of a grating illuminated by multiple mutually incoherent quasi-plane wavefront. The fringe patterns are then projected on to the object surface and the deformed grating image is captured by a CCD camera for subsequent analysis. Phase shifting techniques have been employed to determine the phase value. With suitable calibration of the system and the phase value obtained, the surface profile of the objects can be determined. The phase variation is achieved by using a linear translation stage incorporated to the grating. In this study, two specimens are tested to demonstrate the validity of the method. One is a spherical cap with a height of 4 mm, and the other is a coin. The experimental results are compared with results obtained by mechanical stylus method. In the case of the spherical cap the results are also compared with fringe projection method based on Talbot effect. 相似文献
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脉冲响应函数与平面周期物体构成任意光学系统的成象特性研究——理论与实验 总被引:1,自引:1,他引:0
本文首先用线性系统中脉冲响应函数的概念分析了光学系统中平面周期物体的广义Talbot效应,利用我们以前导得的Talbot和Lau成象条件,导出了广义Talbot成象条件,得到十分简洁的系统脉冲响应表示式,然后利用光学系统的线性叠加和相关原理研究了任意光学系统中Talbot效应、Lau效应和多重成象现象及其相互关系,最后讨论了任意光学系统中三者之间的关系,并进行了实验证明。所用方法简单明了。 相似文献
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This communication presents the results of investigation undertaken towards testing the viability of wavelet filtering techniques in analyzing the Lau interferometric fringes. Towards this, the applicability of Haar, Daubechies and Symlet wavelet based filtering schemes have been tested. Of these schemes, the Symlet based filtering scheme gives the best results in terms of improved signal to noise ratio. This scheme is then used to analyze Lau interferograms recorded in the experimental arrangement for tilt angle measurement. The processed interferograms yield improved accuracy and precision of measurement. 相似文献
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Two interferometers are described for investigating phase structures. In both an extended white light source is used for illumination. The operation of the interferometers is based on the Lau effect, which is briefly explained. 相似文献
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An interferometric method for the measurement of parallelism of the end faces of a transparent material is described. It is based on the measurement of fringe displacement caused by the wedge angle of the material by using the Lau effect. 相似文献