共查询到19条相似文献,搜索用时 218 毫秒
1.
<正> 1.菲涅耳型透射全息的一般问题透射全息在记录时,物光和参考光来自记录介质的一侧投射在记录介质上。拍照菲涅耳型全息图时,记录介质位在物光波的菲涅耳衍射区。参考光可以用平面光波、发散或会聚的球面光波。为讨论问题简单,用点物作代表推导全息图的空间频率、物象关系、放大率等。我们将点物的全息图称为基元全息图。图2.1是记录光路。物光和参考光的位相函数为 相似文献
2.
3.
平面波导阵列布喇格光栅及其光辐照制作方法 总被引:2,自引:2,他引:0
本文提出了一种新的平面波导阵列布喇格光栅结构,并给出了在光敏感材料中制作这种波导光栅结构的全息光辐照方法.以LiNbO3:Fe晶体作为光敏感材料,用不同空间频率的双光束干涉条纹辐照后,通过数字全息技术对晶体的光致折射率分布测量和进行的导波衍射测试结果表明,利用这种光辐照方法在光敏感材料中制作平面波导阵列全息布喇格光栅是完全可行的.其显著的导波衍射现象表明,如果在平面波导阵列中制作多重布喇格光栅,有可能使其成为超密集波分复用(UDWDM)系统中波长复用/解复用的核心器件. 相似文献
4.
基于单光束干涉和一般的双光束干涉全息照相实验,本文设计了一种反射透射混合型双光束干涉光路,从理论上分析了两束物光与一束参考光干涉叠加后在全息干板上的强度分布情况,通过对照实验:拍摄只有反射物光的单光束干涉光路、只有透射物光的单光束干涉光路、反射透射混合型双光束干涉光路的全息图,对比分析成像效果,结果表明本文设计的光路拍摄得到的全息图成像更完整、更清晰、层次感更强;并进一步通过控制变量法,改变不同的影响因素,进而提高全息图的成像质量。经过多次探究,结果表明,当使用GS-I型全息干板,使用功率约为2.23mW、波长为632.8nm的氦氖激光器拍摄全息图时,控制曝光时间为15s,反射物光与参考光之间的夹角为25°~35°,透射物光与参考光之间的夹角为20°~30°,反射物光、透射物光与参考光的光强比约为1∶1∶1,全息图整体成像效果最佳。 相似文献
5.
《物理与工程》2018,(6)
首先利用波的叠加与干涉理论,给出正入射单色平面参考光波与球面物光波相干叠加时,在全息底片上形成的干涉场的强度分布,以及线性冲洗下全息图的振幅透过率。然后,采用波前相因子判断法,详细分析不同照明条件下全息图的衍射场。结果表明,采用单色平面波照明全息图时,+1级和-1级衍射波分别对应于原物等大的虚像和实像,二者关于全息图具有镜像对称性。当改变照明平面波的波长、传播方向时,成像的位置会发生相应移动。采用单色球面波照明全息图时,情况较为复杂。+1级和-1级衍射波存在3种情形:分别对应一个虚像和一个实像、一对虚像和一对实像。其中虚像和实像均存在放大、缩小和等大3种可能性。相对于原物或其关于全息图的镜像对称位置,虚像和实像的位置均有移动。全息成像的这些特点,在应用中具有实际意义。 相似文献
6.
菲涅耳数字全息成像系统的脉冲响应分析 总被引:1,自引:1,他引:0
数字全息成像由CCD记录数字全息图后经过计算机数值重建物光波场,这个过程从傅里叶变换角度看等同于数字全息图的频谱分析。讨论了数字成像系统的脉冲响应函数,并分别推导了其实像、虚像、零级像在平面波和球面波照射下的波前复振幅分布。结果表明,实像和虚像是移位的夫琅和费衍射分布,而零级像是CCD光瞳的菲涅耳衍射分布,且与参考光波前分布无关。 相似文献
7.
8.
研究以球面波为参考光时体全息图的相对衍射效率问题,从理论计算中发现,当以球面波为参考光时,体全息图的串扰(cross-talk)性能比用平面波时要略好一些,文章对此进行了分析解释并给出了实验验证。根据分析及实际读出的存储图像,发现球面参考光相对于平面参考光也不引起像质退化。这些特性表明了体全息存储器对于参考光平行度调节的要求并不十分严格。此外,文章还给出了以球面波为参考光时体全息图相对衍射效率的近似解析计算公式。 相似文献
9.
10.
11.
Design of the spatial filter window for digital holographic convolution reconstruction of object beam field 总被引:1,自引:0,他引:1
In the convolution reconstruction process of digital holographic object beam field, the object beam fields with different magnifications can be obtained when the reconstructing beams are spherical waves with different wave curvature radii. This paper presents a theoretical and experimental discussion on the useful spatial frequency spectrum of the hologram numerically illuminated by the spherical wave. The result shows that there would be an image in the spatial frequency spectrum of digital hologram, which is completely the same as the object, if the wave surface radius of the spherical wave is equal to the distance from the object to the CCD sensor. Taking this image as a reference and designing a filter, the position of the reconstructed images with different magnifications can be predicted correctly in the reconstructed plane. Additionally, since the spectrum distribution of zero-order diffraction can be forecasted accurately in theory, its contribution can be effectively eliminated through changing the spatial filter shape; then a reconstructed object field containing more high-frequency information can be obtained. 相似文献
12.
13.
An analytical solution to the system of linear differential equations that describe the reconstruction of object wave using a transmission holographic grating formed in a cubic photorefractive piezoelectric (\(\left( {\overline {11} 0} \right)\))- cut crystal with the 23 symmetry is derived. The solution is used to interpret the experimental results on the dependence of the diffraction efficiency of mixed holograms on the thickness of the Bi12TiO20 crystal at a fixed orientation angle and three azimuths of linear polarization of the readout reference beam. The best agreement of the theoretical and experimental results on mixed holograms is reached when the inverse piezoelectric effect and photoelasticity are taken into account in addition to the conventional electrooptic effect. 相似文献
14.
This paper deals with “waveguide holograms” recorded in a layer of storage material covering a planar dielectric waveguide.
Reference and read-out waves are guided modes of the waveguide. Their field in the storage medium is evanescent. A theory
of the diffraction efficiencies of these waveguide holograms is presented fors-polarized wavefields. To calculate the hologram structure the attenuation of the reference wave caused by absorption in the
light-sensitive storage material is taken into account. Analytical expressions for the local and the overall diffraction efficiencies
and for the intensity profiles of the diffracted fields are derived. The dependence of these quantities on experimental parameters
(the waveguide thickness, the mode numbers of the reference and read-out waves, and the angle of incidence of the plane object
wave) is presented graphically, i.e., by computer plots.
Grating couplers for integrated optics can be made by waveguide holography. We consider this application to be interesting
because incoupling efficiencies for Gaussian beams of up to 96% can be achieved theoretically. 相似文献
15.
The results of the investigation of recording Fourier phase holograms on a self-developing photopolymer photosensitive in the range λ=400–515 nm are presented. It has been found that, due to the transient energy transfer between the beams, noise gratings are recorded, and a corresponding sharp reduction in the signal-to-noise ratio occurs, while the diffraction efficiency of the hologram as a whole remains relatively high (above 50%). It has been found that the noise-grating recording can be substantially suppressed by increasing the intensity of the reference beam relative to the intensity of the object beam. In this way, the signal-to-noise ratio has been considerably improved for Fourier holograms of binary phase masks: at a reference to object beam intensity ratio R=26, Fourier phase holograms are recorded with a diffraction efficiency η=15% and signal-to-noise ratio N=20 dB. 相似文献
16.
A laser beam with phase singularities is an interesting object to study in optics and may have important applications in guiding atoms and molecules. We explore the characteristics of a singularity in a nondiffracting Bessel beam experimentally by use of a programmable spatial light modulator with 64-level phase holograms. The diffraction efficiency with 64-level phase holograms is greatly improved in comparison with that obtained with a binary grating. The experiments show that the size and deflection angle of the beam can be controlled in real time. The observations are in agreement with scalar diffraction theory. 相似文献
17.
The first Born approximation is applied to calculate the angular selectivity for different positions on the reconstructed image as a function of the object beam's optical axis angle theta(ob) and reference beam angle theta(rw) for a holographic data storage system that records the Fourier transform holograms in a medium with an infinite plane-wave reference beam. Results are compared with those calculated by the coupled-wave theory. 相似文献
18.
Yaping Zhang Junchang Li Wenming Yang Jianqiang Zhang Peng Wang Wei Xu 《Optical and Quantum Electronics》2013,45(10):1077-1086
The objective surface is considered as the scattering plane; frequency spectrum of a digital hologram transmission light is studied when the reference light and reconstruction wave are spherical waves. The relation between relevant parameters and the object light, conjugate object light and zero-order diffraction wave frequency spectrum distribution. The research results show that: each frequency spectrum of the diffracted wave broadens to various degrees as the radius of the reconstruction wavefront decreases, and frequency aliasing is generated under certain conditions. Based on the research results, a new method that carries out high-pass filtering processing without zero-order diffraction interference upon digital hologram is proposed and the reconstruction experimental proof for eliminating the interferential changeable magnification wave is given. 相似文献
19.
T. Kubota 《Optics Communications》1976,16(3):347-349
The profile of the hologram grating is described considerating the absorption of the recording medium and its diffraction efficiency is calculated for special cases using the coupled wave theory. The maximum diffraction efficiency obtainable is not affected by the absorption of the recording medium in the case of transmission holograms, while it decreases with increasing absorption in the case of absorptive reflection holograms. 相似文献