Holographic lens recorded on photopolymers: fabrication and study of the image quality

In recent years, holographic optical elements have been introduced in different applications such as high-density data storage, interconnections, spatial and temporal filters and three-dimensional displays. Simultaneously, more sensitive, efficient and durable holographic materials have been developed. Thus it is necessary to analyze the characteristics of these elements in the holographic materials developed. In this paper a method to obtain holographic lenses in a photopolymer is presented. In order to obtain, reconstruct and analyze these lenses, an optical device was designed. Once the holographic lenses are obtained, the device allows us to capture the images provided by these lenses. The imaging quality of these lenses was evaluated by means of the modulation transfer function (MTF) and the contrast. Lenses of different focal lengths were recorded. The holographic lenses obtained had high diffraction efficiency and temporal stability. Moreover, the resolution was greater than that of other lenses with the same diaphragm number.     

调频加网对于全息再现图像的影响

目的 对全息图进行加网处理,实现计算全息图的二值化,将计算全息图应用于印刷领域。方法 本文设计计算全息图进行调频加网的整体方案,讨论不同的加网算法对计算全息再现图像的质量影响。首先,对3幅不同类型的灰度图片进行计算全息编码得到全息图;然后利用误差扩散算法和抖动算法对全息图进行调频加网获得二值化全息图;之后通过光场重建得到全息再现图像。结果 对全息再现图像进行峰值信噪比和结构相似性数据比较发现,误差扩散算法更适用于计算全息二值化处理,抖动加网使计算全息图产生周期性图案,导致再现全息图产生混频现象,全息再现图像的质量下降。结论 加网导致全息图再现质量下降,误差扩散算法可以得到较好的再现像,适用于全息图的二值化处理;与此同时,抖动算法会产生混频现象,因此抖动算法并不适用于全息图二值化处理。     

Application of a photopolymer to a holographic reflector for reflective liquid-crystal displays

A photopolymer for fabrication of volume-type transmission holograms, which are used primarily on the holographic reflector for reflective LCD's, is reported. This photopolymer consists of bisphenol-type epoxy resin and an acrylic monomer with diaryliodonium salt and 3-ketocoumarin as a complex initiator. The chemistry of the imaging formation is based on the radical polymerization of the monomer initiated by a holographic exposure, followed by the cationic polymerization of epoxy resin by UV exposure after postexposure baking. The yellowish color of the hologram derivatives that resulted from the sensitizing dye and from the photospeed were improved to satisfy the specifications for the holographic reflector. The holographic reflector now gives brighter images.     

全息技术在检测技术中的应用

为了解决复杂结构的检测问题,采用以激光技术为基础的全息技术.通过分析全息技术的理论基础、基本过程和实现方法以及全息图的基本特点,讨论全息技术在检测领域中的应用原理、实现方法,特别是在全息金属无损检测和全息振动测试两个方向上,较详细地研究了这两种检测技术的应用原理、实现方法及适用场合,为全息技术在检测领域中实践应用提供一个有价值的理论参考.     

Holographic diffuser by use of a silver halide sensitized gelatin process

Diffusers play an important role in liquid crystal display (LCD) application as a beam-shaping device, a brightness homogenizer, a light-Scattering device, and an imaging screen. The transmittance and diffusing angle of the diffusers are the critical aspects for the applications to the LCD. The holographic diffusers by use of various processing methods have been investigated. The diffusing characteristics of different diffusing materials and processing methods have been evaluated and compared. The microstructures of holographic diffuse have been investigated by use of using scanning electron microscopy. The holographic diffusers by use of the silver halide sensitized gelatin (SHSG) method have the structural merits for the improvement of the quality of diffusers. The features of holographic diffuser were exceptional in terms of transmittance and diffusing angle. The replication method by use of the SHSG process can be directly used for the manufacturing of diffusers for the display application.     

Multi-hump holographic solitons in photorefractive crystals

We find a novel kind of holographic soliton in a Hamiltonian system, which is described by two arbitrary-amplitude components. Various forms of such types of holographic solitons, not only two- but also multi-hump solitons, can be available. Additionally, we find this new type of holographic soliton can act as a bridge to connect the other types of holographic solitons presented previously.     

Write-once recording for multilayered optical waveguide-type holographic cards

We propose a write-once recording technique for multilayered optical waveguide-type holographic cards. The card medium has a construction created by adding a recording layer and a holographic grating layer to the multilayered optical waveguide composed of core and cladding layers. Individual data for each medium were recorded as an arrangement of optically transparent holes formed in the recording layer. Holograms common to all media were designed in the holographic grating layer so that diffracted lights from the holograms could pass through the holes and focus on an image sensor. We succeeded in write-once recording with a memory capacity potential of more than 128 bits.     

pH-sensitive holographic sensors

Holographic sensors for monitoring H+ (pH) have been fabricated from ionizable monomers incorporated into thin, polymeric, hydrogel films which were transformed into volume holograms using a diffusion method coupled with holographic recording, using a frequency doubled Nd:YAG laser (532 nm). Unlike other optical pH sensors, it is possible to tailor the operational replay wavelength of the holographic sensor by careful control of the exposure conditions. The holographic diffraction wavelength (color) of the holograms was used to characterize their shrinkage and swelling behavior as a function of pH in various media. The effects of hydrogel composition, ionic strength, temperature, and factors influencing reversibility and response time are evaluated. Optimized holographic pH sensors show milli-pH resolution. The pH-sensing range of the holograms can be controlled through variation of the nature of the ionizable co-monomer used in polymer film construction; a series of holographic sensors displaying visually perceptible, fully reversible color changes over different pH ranges are demonstrated. A poly(hydroxyethyl methacrylate-co-methacrylic acid) holographic sensor was shown to be able to quantify the change in H+ concentrations in real time in a sample of milk undergoing homolactic fermentation in the presence of Lactobacillus casei.     

抗几何攻击的强鲁棒性全息水印研究

目的寻找一种能够抵抗常见几何攻击的安全的水印算法。方法通过分析常见的水印算法,发现傅里叶-梅林变换域水印能够较好地满足抵抗常见几何攻击的需求。对水印图像进行双随机相位全息加密,通过密钥保障水印的安全性,通过把加密的水印嵌入到傅里叶-梅林变换域的方法,设计对比试验,研究含有水印的图像在平移、缩放、旋转、中值滤波、高斯噪声、椒盐噪声、压缩、打印扫描、打印拍摄攻击下提取水印质量的影响。结果水印能够抵抗常见的几何攻击,特别对平移、缩放、旋转组合几何攻击、打印扫描和打印拍摄有很好的效果。结论基于傅里叶-梅林变换的全息水印算法具有很好的鲁棒性,能够抵抗常见的几何攻击;具有很好的安全性,没有密钥不能对水印进行检测和去除。     

Holographic scattering in SiO2 nanoparticle-dispersed photopolymer films

We describe an experimental study of holographic (coherent) scattering due to parasitic noise gratings recorded in SiO2 nanoparticle-dispersed photopolymer films. Dependences of film thickness and nanoparticle concentration on holographic scattering losses are evaluated. It is shown that the geometric feature of the holographic scattering pattern in the two-beam recording setup can be explained by the Ewald sphere construction. It is found that holographic scattering becomes noticeable when a film with nanoparticle concentrations higher than 10 vol.% is thicker than 100 microm. The significance of holographic scattering in the characterization of a volume grating recorded in a thick (>100 microm) nanoparticle-dispersed photopolymer film is also discussed.     

Investigation of AGFA-8E56HD photographic emulsion and relief hologram structures by atomic force microscopy

Relief holograms are obtained on Agfa 8E56HD holographic emulsions by a Russian chemical-processing technique that is developed for their PE-2 holographic emulsion. We have shown that the three-dimensional surface profiles can easily be visualized by applying atomic force microscopy to measurement of the relief depth and relief spacing on holographic emulsions. The relief depth and thus diffraction efficiency decreases with increasing exposure time.     

Digital holographic microscopy for live cell applications and technical inspection

Digital holographic microscopy enables a quantitative phase contrast metrology that is suitable for the investigation of reflective surfaces as well as for the marker-free analysis of living cells. The digital holographic feature of (subsequent) numerical focus adjustment makes possible applications for multifocus imaging. An overview of digital holographic microscopy methods is described. Applications of digital holographic microscopy are demonstrated by results obtained from livings cells and engineered surfaces.     

Messung der Verformung an Elektronenstrahlschweißnähten mit Hilfe der holografischen Interferometrie

Measurement of the Deformations of EB-welded Joints by the Means of Holographic Interferometry. The field of deformations in EB-welded specimens should be measured in all directions. Therefore holographic interferometry was chosen to be the best method. Normally the deformations are so large, that the usual fringe systems cannot be solved. In order to avoid this difficulty, new diagrams were developed and based on this the holographic equipment was optimized. By means of the new diagrams and some derived diagrams it was possible, to calculate the deformations very easily. In addition a specimen-holder is described which allows the specimen to be taken out of the holographic system during the welding process.     

Comparison of mechanically ruled versus holographically varied line-spacing gratings for a soft-x-ray flat-field spectrograph

Recent progress in the design of aspheric wave-front recording systems has permitted the manufacture of holographic gratings with highly variable groove densities that are suitable for flat-field spectrographs. A holographic grating thus recorded was processed to produce a laminar profile by use of reactive-ion etching. Measurements are reported of the absolute diffraction efficiency of this grating and of a comparable mechanically ruled grating. It is found that the holographic grating is much more effective in suppressing the higher orders. The spectral resolution was determined by use of a carbon Kalpha x-ray generator and a spectrograph with an imaging detector. The spectral resolution of the holographic grating was approximately 3 times worse than that of the ruled grating.     

采用包络检波去除SISAR直达波干扰的新方法

为了去除直达波干扰，从强的直达波干扰背景中有效提取SISAR侧影成像的目标全息信号，提出了对接收的含有目标全息信号和强直达波的混合信号直接进行包络检波，然后通过对检波后的输出进行时域的正交分解，恢复目标的全息信号的新方法．仿真结果验证了理论分析的正确性。     

基于归一化的全息水印技术

提出了一种结合了归一化技术和全息技术的数字水印技术。首先,利用归一化技术对图像作归一化运算,同时利用全息技术将水印二值图处理为全息图;其次,取归一化后图像分块离散余弦变换的中频系数,对中频系数所组成的矩阵作离散小波变换;最后将全息图嵌入到离散小波变换的低频分量中。由于图像归一化技术具有抗仿射变换的性能,同时全息技术具有很强的抗裁切的性能,所以此数字水印技术具有很强的抗仿射变换的性能,可以广泛的用于数字作品的版权保护。     

Betriebsnahe Schadenserkennung mit Hilfe der holografischen Interferometrie und eines Doppelimpulslasers

Holographic Investigation on Failure Mechanisms in Homogenous Materials There is a relation between defects occuring in the wall material of pressurized equipment and the deformation of wall surface under load. If the deformation at the surface exceeds 35 nm, it is possible to use holographic interferometry for detection. The object is illuminated by a double pulsed ruby-laser. The frequency of the flashes is very large. Therefore it is not necessary to use of a stabilized holographic equipment. In this way it is possible to detect damage progression in the material of equipment during operation with non-destructive methods. Usually the severity of a failure is characterized by the apparent perturbation of its holographic fringe pattern. The method is applicable to pressure vessels, if the holographic taken fringe pattern is related quantitatively to the size of a failure. In this report we present the experimental results which give the relation between the perturbation of the holographic fringes and the size of different kinds of failures. The size of the smallest detectable failure is smaller the critical size of a flaw in the material.     

Rainbow holographic aberrations and the bandwidth requirements

Rainbow holographic image resolution, primary aberrations, and bandwidth requirements are presented. The results obtained for the rainbow holographic process are rather general, for which the conventional holographic image resolution, aberrations, and bandwidth requirements, can be derived. The conditions for the elimination of the five primary rainbow holographic aberrations are also given. These conditions may be useful for the application of obtaining a high-quality rainbow hologram image. In terms of bandwidth requirements, we have shown that the bandwidth requirement for a rainbow holographic construction is usually several orders lower than that of a conventional holographic process. Therefore, a lower-resolution recording medium can generally be used for most of the rainbow holographic constructions.     

Holographic image storage in eu(3+)-doped alkali aluminosilicate glasses

We demonstrate that holographic information can be stored in Eu(3+)-doped alkali aluminosilicate glasses. The holograms were developed by a two-beam mixing configuration with a write-beam wavelength (465.8 nm) corresponding to the (7)F(0) ? (5)D(0) transition of the Eu(3+) ions. The images were reconstructed either with the wavelength used to record them or with wavelengths below this transition (543.5 and 632.8 nm). We stored clear holographic images using a total writing power of 5 mW and an exposure time of 20 s. In addition, clear holograms were recorded with an exposure time of 200 ms when 100 mW of the writing power was used. The exposure time and the writing power required to obtain clear holographic images are dependent on the Eu(3+) concentration.     

Scanning holographic microscopy with transverse resolution exceeding the Rayleigh limit and extended depth of focus

We demonstrate experimentally that the method of scanning holographic microscopy is capable of producing images reconstructed numerically from holograms recorded digitally in the time domain by scanning, with transverse and axial resolutions comparable to those of wide-field or scanning microscopy with the same objective. Furthermore, we show that it is possible to synthesize the point-spread function of scanning holographic microscopy to obtain, with the same objective, holographic reconstructions with a transverse resolution exceeding the Rayleigh limit of the objective up to a factor of 2 in the limit of low numerical aperture. These holographic reconstructions also exhibit an extended depth of focus, the extent of which is adjustable without compromising the transverse resolution.