共查询到20条相似文献,搜索用时 46 毫秒
1.
A new class of holography is proposed, in which (1) the evanescent part of a guided wave, or (2) the guided wave in a thin-film hologram is utilized as the reference wave and/or the illuminating one. The hologram was designated as “wave-guide hologram” and has advantages in the possibility of integration, wide field of view, and compactness and high reliability of the reconstructing system. The possibility of the waveguide hologram has been proved through reconstruction experiments with a guided wave of a waveguide hologram recorded with a plane reference wave. 相似文献
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光纤像面全息可以获得较高衍射效率的全息图和再现较大的物像。文中分析了相干光激励下传像光纤束单丝芯径的大小对其输出光场的影响,以及输出光场中低阶模与高阶模对全息照相的不同作用,在此基础上,提出缩小传像束单丝芯径,增多单丝根数,可以提高光纤像面全息图衍射效率和分辨率的观点,并通过实验进行了验证。 相似文献
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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. 相似文献
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L. Janićijević 《Optical and Quantum Electronics》1985,17(2):125-138
Realized as an interferogram of a spherical and a cylindrical wave, the elliptical hologram is treated as a plane diffracting grating which produces Fresnel diffraction of a simple astigmatic gaussian incident wave. It is shown that if the principal axes of the incident beam coincide with the principal axes of the hologram, the diffracted wave field is composed of three different astigmatic gaussian waves, with their waists situated in parallel but distinct planes. The diffraction pattern, observed on a transverse screen, is the result of the interference of the three diffracted wave components. It consists of three systems of overlapped second-order curves, whose shape depends on the distance of the observation screen from the hologram, as well as on the parameters of the incident wave beam and the hologram. The results are specialized for gratings in the form of circular and linear holograms and for the case of a stigmatic gaussian incident wave, as well as for the normal plane-wave incidence on the three mentioned types of hologram. 相似文献
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Planar nearfield acoustic holography (NAH) is extended to identify the sound source in a noisy environment. The extended method requires the knowledge of the pressures on two closely spaced parallel hologram planes and the plane wave reflection coefficient on the target source surface. First, the incoming field coming from the back side of the microphone array and the scattered field due to the incoming wave falling on the target source are correlated through the plane wave reflection coefficient on the target source surface. Then, the mixed field on the hologram plane can be represented by the field that would be radiated by the target source into free space and the incoming field. Finally, the field that would be radiated by the target source into free space can be extracted by using the pressures measured on two hologram planes, which will be further used to accurately identify the sound source via planar NAH. The validity of the proposed method is demonstrated by simulations and experiment, and the influence of the relative strength of the disturbing source to the target source is also investigated. 相似文献
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V. G. Gusev 《Russian Physics Journal》2005,48(10):1064-1068
The conditions for lateral-shear interferogram formation in diffusively scattered fields are analyzed taking into account
hologram aberrations for the case of transverse displacement of a mat screen and a negative lens before second photoplate
exposure. It is shown that the error of control of wave aberrations of the negative lens results at the hologram reproduction
stage when the diffusive field is subject to an off-axis spatial filtering.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 58–62, October, 2005. 相似文献
10.
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. 相似文献
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It is shown that under uniform illumination and application of an external electric field, a phase volume hologram in a photorefractive crystal exists in the form of relaxing running wave. Effective recording of such a running hologram is possible only by an interference pattern moving synchronously with the recorded grating. The physical nature of this phenomenon, the possible enhancement of the hologram diffraction efficiency upon recording of a running pattern and the main factors limiting its value are discussed for the case of photorefractive Bi12SiO20 crystals. 相似文献
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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
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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. 相似文献
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V. V. Orlov 《Optics and Spectroscopy》2002,92(5):795-799
The wave field arising in the volume of superposed holograms is obtained with allowance for multiple wave diffraction on holographic cross-modulation gratings. It is shown that cross-talk interference waves are generated as a result of multiple diffraction, and their intensity depends on the degree of mutual orthogonality of hologram object waves. 相似文献
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体全息对小粒子记录及再现的影响关系到体全息材料在粒子场检测领域的应用前景,提出结合角谱传播理论与多光栅耦合波理论进行体全息图衍射分析的方法,并数值模拟了微米量级小粒子衍射光场的体全息记录与再现。数值分析结果表明体全息理论并不能像薄全息理论那样精确的再现出原始物光。其再现光场的角谱分布相对于原始光场存在高阶衰减,这使得再现光场成像后的图像边缘模糊,而且模糊程度还会随着粒子尺寸的下降逐渐上升。虽然这一现象为粒子边缘判读带来困难,但是再现图像的径向强度分布可为提高判断精度提供有益的参考。 相似文献
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A spatial-frequency version of high efficiency three-dimensional holograms of complex wave fields has been achieved. It has been shown that a three-dimensional hologram recorded by a plane reference wave may be described by means of a complex transfer function, which is found here analytically. Analysis of amplitudephase wave field distortions, under different recording and reconstruction conditions, has been carried out. 相似文献
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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. 相似文献
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A scheme for recording fast process at nanosecond scale by using digital holographic interferometry with continuous wave (CW) laser is described and demonstrated experimentally, which employs delayed-time fibers and angular multiplexing technique and can realize the variable temporal resolution at nanosecond scale and different measured depths of object field at certain temporal resolution. The actual delay-time is controlled by two delayed-time fibers with different lengths. The object field information in two different states can be simultaneously recorded in a composite hologram. This scheme is also suitable for recording fast process at picosecond scale, by using an electro-optic modulator. 相似文献