- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Optical Performance Degradation Effects by Fabrication Errors of Circular-type Computer Generated Holograms
摘要： A null test method which relies on a computer generated hologram (CGH) is widely used to measure a large aspheric surface. For precise measurements of the surface shape of an aspheric optics, the CGH must precisely generate a wavefront that can fit on the ideal surface shape of the aspheric optics. If fabrication errors arise in the CGH, an unwanted wavefront will be generated and the measuring result will lack trustworthiness. Thus far, there has been limited research on wavefronts generated by CGH using only linear-type binary grating models. In this study, a theoretical error model of a circular-type zone plate, the most commonly used types for CGH patterns, is suggested. The proposed error model is checked by simulations and experiments.
关键词： Optical performance degradation,Computer generated hologram
更新于2025-09-23 15:23:52
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Even-odd effect in higher-order holographic production of electron vortex beams with nontrivial radial structures
摘要： Structured electron beams carrying orbital angular momentum are currently of considerable interest, both from a fundamental point of view and for application in electron microscopy and spectroscopy. Until recently, most studies have focused on the azimuthal structure of electron vortex beams with well-defined orbital angular momentum. To unambiguously define real electron-beam states and realize them in the laboratory, the radial structure must also be specified. Here we use a specific set of orthonormal modes of electron (vortex) beams to describe both the radial and azimuthal structures of arbitrary electron wavefronts. The specific beam states are based on truncated Bessel beams localized within the lens aperture plane of an electron microscope. We show that their Fourier transform set of beams can be realized at the focal planes of the probe-forming lens using a binary computer-generated electron hologram. Using astigmatic transformation optics, we demonstrate that the azimuthal indices of the diffracted beams scale with the order of the diffraction through phase amplification. However, their radial indices remain the same as those of the encoding beams for all the odd diffraction orders or are reduced to the zeroth order for the even-order diffracted beams. This simple even-odd rule can also be explained in terms of the phase amplification of the radial profiles. We envisage that the orthonormal cylindrical basis set of states could lead to new possibilities in phase contrast electron microscopy and spectroscopy using structured electron beams.
关键词： truncated Bessel beams,astigmatic transformation,computer-generated hologram,electron vortex beams,orbital angular momentum,phase amplification
更新于2025-09-23 15:22:29
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Optical implementation of image encryption based on digital holography and computer generated hologram
摘要： An experimental implement method of optical image encryption based on digital holography and computer generated hologram(CGH) is proposed in this paper. The actual object is encrypted by double random phase in the digital holography system and CGH encoding process, after that the decryption is achieved in optical Fourier transform and Fresnel diffraction system based on spatial light modulator(SLM). In this method, both physical and digital images can be encrypted in optical system. Meanwhile, besides the double random phase keys, Fresnel diffraction distance, wavelength key in digital holography system and CGH coding parameters improve the security. Experimental results are in agreement with numerical calculations which shows the feasibility and practicability of proposed experimental method.
关键词： optical image encryption,computer generated hologram,digital hologram
更新于2025-09-23 15:21:01
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Holographic Femtosecond Laser Processing for Fabricating Three-Dimensional Structures; ホログラフィックフェムト秒レーザー加工による3次元微細構造の作製;
摘要： Holographic Femtosecond Laser Processing for Fabricating Three-Dimensional Structures
关键词： Spatial Light Modulator,3D Printing,3D Device,Computer-Generated Hologram
更新于2025-09-12 10:27:22
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Study on Compact Head-Mounted Display System Using Electro-Holography for Augmented Reality
摘要： Head-mounted displays (HMDs) and augmented reality (AR) are actively being studied. However, ordinary AR HMDs for visual assistance have a problem in which users have di?culty simultaneously focusing their eyes on both the real target object and the displayed image because the image can only be displayed at a ?xed distance from an user’s eyes in contrast to where the real object three-dimensionally exists. Therefore, we considered incorporating a holographic technology, an ideal three-dimensional (3D) display technology, into an AR HMD system. A few studies on holographic HMDs have had technical problems, and they have faults in size and weight. This paper proposes a compact holographic AR HMD system with the purpose of enabling an ideal 3D AR HMD system which can correctly reconstruct the image at any depth. In this paper, a Fourier transform optical system (FTOS) was implemented using only one lens in order to achieve a compact and lightweight structure, and a compact holographic AR HMD system was constructed. The experimental results showed that the proposed system can reconstruct sharp images at the cor- rect depth for a wide depth range. This study enabled an ideal 3D AR HMD system that enables simultaneous viewing of both the real target object and the reconstructed image without feeling visual fatigue.
关键词： augmented reality,electro-holography,head-mounted display,computer-generated hologram
更新于2025-09-12 10:27:22