Microcomputer-generated holograms

A microcomputer system consisting of a personal computer and a plotter has been used to produce good quality computer-generated holograms of the Lohmann type.     

Full-view rainbow-reflection holograms

A simple method of recording full-view rainbow-reflection holograms on a single flat plate is described: only one white-light illuminating source is required in the reconstruction process. The hologram can be viewed from opposite sides, where each side of a three-dimensional object, with its original spatial relationship, is displayed in bright colours.     

二次再现全息图

目前 ,光学防伪技术已广泛应用于钞票、信用卡、各种证件和高档商品上。全息术是一种被广泛认知的光学防伪技术 ,编码加密技术是提高它防伪功能的重要手段。二次再现全息图是根据全息图能够进行多次记录和多次再现的特点提出的一种加密全息图。在一定的照明条件下 ,它的再现光经过一个平面反射镜的反射返回到全息图 ,作为它的第二束照明光 ,这时能够再现出被加密的图像。它是由一个像全息图和一个参考光编码全息图组合而成的。一般情况下 ,二次再现全息图存在再现光路恢复困难的问题。利用低频光栅能够较好地解决这一问题 ,使二次再现全息图达到实用性的要求。该技术用于防伪产品可提高它的防伪力度。给出了详细的理论分析、制作方法和实验结果     

Multiple object-beam holograms

A multiple object-beam holography is proposed, where a two-dimensional rectangular amplitude grating and a phase plate of matrix form placed at the frequency plane of the grating constitute the main parts of a speckle-free periodic illumination system of continuous tone transparencies. Demonstration experiments are made, where the number of diffracted orders of the grating, the ratio of the widths of transparent and opaque zones of the grating, the retardation of each matrix zone of the phase plate and the distance between planes of the image of the grating and a transparency are taken as variables.     

High-efficiency detour-phase holograms

We suggest a new approach to the fabrication of detour-phase holograms. By combining the concept of the detour phase with highly efficient carrier gratings it is possible to overcome the major drawback of detour-phase holograms, i.e., their low efficiency. We call the new hologram type a kinoform detour-phase hologram (KDPH). KDPH's facilitate the implementation of diffractive elements with high phase complexity. Especially if off-axis reconstruction is desired, the number of degrees of freedom for the design of the phase component is increased significantly.     

Deciphering vibration holograms

In vibration holography one measures the temporal Fourier coefficients of the complex amplitude emanating from the vibrating object. However, the user wants to know the temporal Fourier coefficients of the mechanical vibration itself. The mechanical vibrations are proportional to the phase of the complex light amplitude. Hence, the temporal Fourier coefficients of the mechanical vibrations depend in a complicated manner on the temporal Fourier coefficients of the complex amplitude itself. So far, either narrow approximations or complicated Bessel algorithms were used for deducing the mechanical Fourier coefficients from the optical Fourier coefficients. In other words, deciphering the mechanical data from the optical measurements was not easy.We propose a simple and rigorous algorithm for this deciphering project. In addition we outline a holographic experiment that allows one to reconstruct a space- and time-dependent complex amplitude and also its temporal derivative. This experiment is capable of displaying the mechanical velocity distribution as image brightness. Also the spatial distribution of mechanical acceleration can be displayed.     

Corn syrup holograms

A study of the diffraction efficiency parameter, of holographic gratings recorded with thin emulsion layers of corn syrup (Karo^®) photosensitized with potassium dichromate salt is presented. This was possible by the interference produced by amplitude division setup using two wavelengths at 473 nm and 530 nm respectively. The maximum diffraction efficiency for corn syrup with potassium dichromate films was on average in the order of 4.0% at first diffraction order. The energy that was applied at blue light was 10 times less than that applied at green light.Evolution in the behavior profile from the diffraction efficiency parameter is presented as a function of relaxation time necessary to obtain major performance of these gratings made with peculiar sweetener.Holograms with this material do not require developing processes, because these samples develop by themselves. After of exposition with light laser, is necessary wait to stabilize the material 96 h, to protect the film against the environmental humidity.     

Bleached reflection holograms

By applying recently developed, low-noise, processing techniques, high quality, bleached, reflection holograms of three-dimensional objects have been produced with a commercial photographic emulsion. When illuminated with a compact, white light source, these holograms give bright, reconstructed images with a signal-to-noise ratio which compares very favourably with that for unbleached, transmission holograms.     

Nonlinear computer-generated holograms

We propose a novel technique for arbitrary wavefront shaping in quadratic nonlinear crystals by introducing the concept of computer-generated holograms (CGHs) into the nonlinear optical regime. We demonstrate the method experimentally showing a conversion of a fundamental Gaussian beam pump light into the first three Hermite-Gaussian beams at the second harmonic in a stoichiometric lithium tantalate nonlinear crystal, and we characterize its efficiency dependence on the fundamental power and the crystal temperature. Nonlinear CGHs open new possibilities in the fields of nonlinear beam shaping, mode conversion, and beam steering.     

Computer-generated true-color rainbow holograms

A new method of calculating computer-generated true-color rainbow holograms (CGTCRH) is proposed. This technique allows the true-color object reconstruction. The main idea of the presented work is based on the additive properties of holographic wavefront reconstruction such that the resulting hologram is a superposition of three (or more) holograms, with each of them producing different color reconstruction of the same object. White light and monochromatic light reconstruction results are discussed.     

图案可控动态莫尔全息图

提出了一种条纹移动及形状变化都能预先设定的图案可控动态莫尔全息图的设计方法和制作技术。这种图案可控动态莫尔全息图能够产生旋转、放缩、变换等动态效果。给出了详细的理论分析和实验结果。它是一项非常实用的技术 ,用该技术制作的全息图防伪能力显著提高 ,而且容易目视鉴别     

模压全息图的再现过程

本文就模压全息图的再现过程进行了论述。由于模压全息图的特殊性，本文论述了模压全息图再现时的一些现象，这对于设计２Ｄ／３Ｄ模压全息图有一定的参考意义。     

Improving binary computer holograms

We discuss three algorithms for computer-generating binary holograms. These algorithms yield holograms with differing aperture distributions. Reconstructions from these three hologram types are experimentally compared for image detail and diffraction efficiency. We conclude that the form we term modular-overflow-corrected yields the highest diffraction efficiency and the form we term $\text{3}\text{2}$|order yields the best image detail of the hologram types compared.     

Efficiency-enhanced reflective nanosieve holograms

Photon nanosieves, as amplitude-type metasurfaces, have been demonstrated usually in a transmission mode for optical super-focusing, display, and holography, but the sieves with subwavelength size constrain optical transmission, thus leading to low efficiency. Here, we report reflective photon nanosieves that consist of metallic meta-mirrors sitting on a transparent quartz substrate. Upon illumination, these meta-mirrors offer the reflectance of ～50%, which is higher than the transmission of vis...     

UHU adhesive holograms replication

It is possible to apply a new recording material with high diffraction efficiency (of the order of 82.3%) to replicate computer phase or analogical holograms. This material is the all purpose adhesive UHU^®. It is constituted by some components of polyvinyl, nitrates and some solvent agents; it is easily applied to any substrate. We record this material with heat generation by hand rubbing, using a mask (Kodalith^® films) manufactured with lithographic techniques. The holographic replication is excellent on the new material UHU^® adhesive, showing a phase modulation for refraction index and relief. This modulation is determined by the cured polymers process induced by friction, as pressure and temperature, with an anaerobic reaction.For copy of conventional holograms at high frequencies (holographic ranges), the diffraction efficiency parameter is in the neighborhood of 19.1% at first order or more, depending on diffraction efficiency of the pattern of the hologram. The hologram is elaborated in the absence of any development process and does not need to have carefully controlled conditions of the environment. Following this process, the hologram is obtained at standard atmospheric conditions of pressure and temperature.     

可分离再现的双脉冲曝光全息图

本文提出一种可以分别再现双脉冲曝光粒子场全息图的两幅图像的技术,记录全息图时,利用电光晶体和偏振分光棱镜,使两个光脉冲的物光波或参考光波沿不同的空间路径到达全息底板,从而通过不同的空间滤波在再现全息图时分别获得对应于不同脉冲时刻的粒子场图像.实验证实了该技术的可行性.