Hologram recording and read-out with the evanescent field of guided waves

We investigate hologram recording and read-out where the evanescent field of a guided mode propagating in a planar waveguide is used as reference and illuminating wave, respectively. A special case of such a hologram is a new type of grating coupler promising beam to mode coupling with high coupling efficiency. First experiments with dichromated gelatin as the recording medium are reported as feasibility proof.     

Reconstruction of synthesized holograms-Fresnel projectors at angles of incidence of reconstructing wave that exceed the angle of incidence of the reference wave in hologram synthesis

The possibility of the aberration-free reconstruction of a synthesized hologram-Fresnel projector in the case when the angles of incidence of the reconstructing plane wave exceed the angle of incidence of the plane reference wave during hologram synthesis is shown. The character of the dependence of admissible angles of incidence of the reconstructing wave on the parameters of the synthesis of hologram projectors is revealed and described mathematically. The results of an experimental study that confirms the possibility of the aberration-free reconstruction of hologram projectors at angles of incidence of the reconstructing plane wave that exceed the angle of incidence of the reference wave of the plane are presented. The results of the successful implementation of the projection photolithography process using a synthesized relief-phase reflection hologram-Fresnel projector are demonstrated.     

以球面波为参考光的体全息图衍射特性研究

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。     

Recording and reconstruction of digital Gabor hologram

This paper looks at some as yet undisclosed observations in the recording and reconstruction of digital Gabor hologram. Small particles on the specimen plane diffract the illuminating spherical wave to form the object wave which interferes with the un-diffracted reference to form the in-line hologram. The interference is similar to that between two spherical wavefronts. It is shown that resolution enhancement can be achieved in the recording process through the use of wavefronts with different curvature. Numerical reconstruction of this hologram with a conjugate of the illuminating (reference) wave provides the in-focus real image at the object plane. It is exemplified that the proper choice of the reconstruction wavefront can optically magnify the reconstructed image enabling one to better visualize the resolution enhancement. Both theoretical analysis and experimental confirmation are provided for these observations.     

Polarization-holographic reversal of the front of a reconstructed wave

The formation of an image by a wave conjugate to the reference wave is considered theoretically. It is shown that the polarization hologram formed upon summation of two beams with mutually orthogonal circular polarizations does not yield conjugate or ghost images in the course of reconstruction. The application of the photoinduced anisotropy in polarization-sensitive dynamic media for the correction of laser radiation with a complex polarization distribution over the wavefront is proposed and tested experimentally. The installation of polarization-holographic correctors both outside the cavity and in the intracavity volume of the laser provides the possibility of achieving divergences close to the diffraction limit at a high energy output.     

Fully phase multiple-image encryption based on superposition principle and the digital holographic technique

We propose an optoelectronic image encryption and decryption technique based on coherent superposition principle and digital holography. With the help of a chaotic random phase mask (CRPM) that is generated by using logistic map, a real-valued primary image is encoded into a phase-only version and then recorded as an encoded hologram. As for multiple-image encryption, only one digital hologram is to be transmitted as the encrypted result by using the multiplexing technique changing the reference wave angle. The bifurcation parameters, the initial values for the logistic maps, the number of the removed elements and the reference wave parameters are kept and transmitted as private keys. Both the encryption and decryption processes can be implemented in opto-digital manner or fully digital manner. Simulation results are given for testing the feasibility of the proposed approach.     

合成孔径数字全息的分析模拟及多参考光合成孔径数字全息

分析了合成孔径数字全息的理论和实现方法,提出了多参考光合成孔径数字全息方法及其应用前景,以双狭缝为例,模拟了单幅及单参考光、多参考光两种合成孔径数字全息术的记录和再现方法,对三种方法再现像的分辨率进行了比较.     

Recording Fractional Fourier Transform Hologram Using Holographic Zone Plate

FRTH(fractional Fourier transform hologram) is a new kind of hologram that differs from common Fresnel holograms and Fourier transform holograms. Due to the flexibility of zone plate. A method that uses the -1 order diffraction wave of zone plate as the object wave and the 0 order diffraction wave as the reference wave to record FRTH is presented. It provides a new simple way to record FRTH. In this paper, the theory of achieving FRT and recording FRTH using holographic zone plate is presented and experimental results are given.     

Recording Fractional Fourier Transform Hologram Using Holographic Zone Plate

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Effect of intensity quantization level in parallel phase-shifting digital holography

Parallel phase-shifting digital holography (PPSDH) enables the instantaneous recording of three-dimensional fields. The three-dimensional field can be reconstructed using a computer by numerical scalar wave propagation. In PPSDH, we record a space-division multiplexed hologram that includes the required phase retardation in the spatial distribution of the reference wave and then interpolate the data at blanked pixels for each phase retardation to obtain the complex amplitude distribution of an object wave. The recorded quality of the multiplexed hologram influences the reconstruction quality. In this study, we investigate the effect of the intensity quantization of a multiplexed hologram on the reconstruction quality. We compare the influence of intensity quantization in PPSDH with that in the conventional phase-shifting method. Random noise is also added to the multiplexed hologram. The required intensity quantization level is helpful for selecting a digital image sensor.     

数字全息用于光波衍射传播理论教学研究

数字全息技术是基于传统光学全息原理,借助于光电探测和数字处理技术,通过单次曝光记录和再现物光场的振幅和相位信息,近年来被广泛研究和应用.将数字全息应用于光波衍射传播理论教学中,不仅能够使学生在学习过程中形象、直观的理解光波衍射传播理论,而且能够通过编程计算完成数字全息图的数值再现,锻炼他们的知识运用能力,从而拓宽专业知识面、了解科学的发展前沿.     

Enhanced angular selectivity in volume holograms with speckle reference waves

A speckle-multiplexing scheme with enhanced angular selectivity for holographic storage is proposed. Angular selectivity in the proposed holographic storage system is theoretically and experimentally investigated. We find the effect of speckle reference wave on angular selectivity strongly depends on the techniques to perform multiplexing for holographic storage. Angular selectivity of a holographic storage system can be effectively enhanced as long as angular deviation of reading wave induces a lateral displacement of the speckle pattern on the hologram plane. When angular deviation of reading wave only induces a speckle wavefront tilt on the hologram plane, the speckle wave is not helpful to enhance the angular selectivity and the angular selectivity becomes to depend on material thickness (Bragg condition) only.     

The surface ace plasmon resonance effect in holography

A hologram has been made using a surface plasmon resonance wave as the reference beam. The surface wave was stimulated on a 1200-line/mm aluminum reflection grating that was coated with a thin layer of high resolution photographic emulsion. Experimental results are presented.     

大尺寸物光波面彩色数字全息高质量重建研究

为解决检测面尺寸较大时CCD难以得到高质量数字全息图的问题,本文利用负透镜设计光学系统让CCD接收来自物体的缩小虚像,以球面波为参考波,使用单色CCD近距离得到三种色光照射下的大尺寸彩色物体的数字全息图,然后采用可控放大率波面重建算法得到同一尺寸的数字全息重建像,合成彩色数字全息重建像.同时,使用两种消零级方法去除零级...     

大尺寸物光波面彩色数字全息高质量重建研究

为解决检测面尺寸较大时CCD难以得到高质量数字全息图的问题,本文利用负透镜设计光学系统让CCD接收来自物体的缩小虚像,以球面波为参考波,使用单色CCD近距离得到三种色光照射下的大尺寸彩色物体的数字全息图,然后采用可控放大率波面重建算法得到同一尺寸的数字全息重建像,合成彩色数字全息重建像.同时,使用两种消零级方法去除零级干扰,提高重建像质量,一种方法利用空间光调制器相移技术在参考光中加入一次任意相移,记录两幅数字全息图,消除重建零级像|另一种方法使用“无干扰全息图”消除重建零级像及共轭像.本文讨论结果可为大物体彩色数字全息及多波长数字全息检测应用提供有益的参考.     

Holography with guided optical waves

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.     

一种基于数字全息技术的盲音频水印算法

提出了一种基于数字全息技术的盲音频水印算法.水印图像经随机相位调制形成物光波,该物光波的傅里叶变换与参考光波发生干涉,形成傅里叶变换全息图.再利用离散余弦变换的能量压缩能力,通过量化算法把降维的水印,即傅里叶变换全息图嵌入音频信号中,在水印提取过程中不需要原始音频信号的参与.仿真实验表明,该算法对低通滤波、噪音干扰特别是剪裁具有一定的稳健性.     

点源参考光数字全息的频谱和记录能力分析

基于最高空间频率分析法,对点源参考光数字全息的空间频谱进行了分析,得出了使空间频谱分离的条件。结合全息成像系统的分辨率,推导出了同时满足采样和再现像分离的记录条件以及CCD对被记录物体的数据记录能力。结果表明,对给定的物体和CCD来说,采用点源参考光比采用平面参考光更容易满足采样和分离的条件,并可以记录到更多的物体信息,从而可使再现像获得更高的分辨率。     

The reconstruction of diffractive object digital hologram at a short distance

By using a spherical wave as the reference wave, we recorded the in-line phase-shifting digital hologram of the 25th element of Chinese standard No. 3 resolution test pattern, and gave the corresponding numerical reconstructed results. Some problems concerning with the digital hologram recording and reconstruction of the diffractive object at a short distance are discussed. The experimental result shows that the resolution of the reconstructed image is better than 10μm, which is the limit by using this experimental arrangement.     

预放大数字全息显微系统的特点

为了提高预放大数字全息显微系统的成像质量,采用理论分析与实验验证相结合的方法,分别对采用平面及球面参考光记录的预放大数字全息显微系统进行了研究和比较。结果表明:在通常的实验条件下,系统的横向分辨力主要取决于显微物镜的成像分辨力;记录距离较小时,两种系统的横向分辨力均随着记录距离的增大略有降低;但当记录距离较大时,球面参考光预放大数字全息系统的横向分辨力降低得更为明显,即平面参考光预放大数字全息显微系统较为优越;在记录距离为0的情况下,即像面数字全息成像情况下,两种系统的再现像均具有最高的分辨力,在利用普通工业用传感器条件下,横向分辨力远超过了2.19 m,且像质较好。因此,尽可能减小全息图的记录距离,或者采用像面数字全息系统,可以有效提高数字全息系统的成像分辨力。