Source focusing and coherent imaging of a microscopic object at weak spatial coherence of the synchrotron radiation beam

Experimental results are presented on the measurement of a holographic (phase-contrast) image of a boric fiber (100-μm-diameter boric cylinder with a 20-μm-diameter tungsten core) and on radiation focusing by Fresnel zone plates using the Kurchatov synchrotron radiation source. By comparison of the obtained hologram with theoretically calculated data, the vertical size of the source was determined to be 325 ± 25 μm. This value was also confirmed by measuring the half-width of the direct image of the source. Features of image recording on a photographic film are discussed.     

Digital holography for quantitative phase-contrast imaging

We present a new application of digital holography for phase-contrast imaging and optical metrology. This holographic imaging technique uses a CCD camera for recording of a digital Fresnel off-axis hologram and a numerical method for hologram reconstruction. The method simultaneously provides an amplitude-contrast image and a quantitative phase-contrast image. An application to surface profilometry is presented and shows excellent agreement with contact-stylus probe measurements.     

Improvement of holographic recording property of a Ce: KNSBN crystal by the moving grating technique

The moving grating technique is applied to improve the holographic recording property of the Ce: KNSBN crystal. In the case of extraordinarily polarized recording, the diffraction efficiency at large fringe modulations is enhanced by a factor of up to 35% at the optimum fringe velocity and the fringe modulation dynamic range is improved from m = 0.2 to m = 0.6. In the case of ordinarily polarized recording, a linear holographic reconstruction in the range of m ≤ 0.8 can be achieved by the moving grating at a fringe velocity of 9.6 nm/s. These results are significant in holography where a grey-level object needs to be recorded and reconstructed with high fidelity.     

Huge retardation of grating formation in holographic polymer-dispersed liquid crystals

Phototriggered kinetics is investigated in the dark for holographic polymer-dispersed liquid crystal gratings. Subsequently to holographic recording, the diffraction efficiency first slightly increases, then decreases, and afterwards starts to grow again. The remarkable growth continues for several days until the diffraction efficiency stabilizes at values several times larger than the initial ones. The initial increase is attributed to a dark polymerization reaction as confirmed by electron paramagnetic resonance spectroscopy. The slow process is associated with the kinetics of a phase-separation mechanism. The non-monotonic behaviour of the diffraction efficiency is explained by superposition of refractive-index and extinction modulations. PACS 42.40.Ht; 61.30.Pq; 42.70.Df; 64.70.Md     

Recording of PIV images on photothermoplastic plates

In this paper we explore the possibility of utilizing commercially available photothermoplastic plates as recording support in Particle Image Velocimetry (PIV), to allow real time analysis of recorded data. An experimental apparatus has been developed which allows holographic recording and reconstruction of simulated PIV images. We show that double exposed photothermoplastic plates can successfully be analysed provided that a suitable recording/reconstruction scheme is used.     

One-step, full-view rainbow holograms with conventional plates of 6 μm emulsion

A method of one-step full-view rainbow holography using conventional holographic plates of 6 °m emulsion as recording materials is described aand experimentally demonstrated. The requirement for the inter-beam angle to avoid cross-talk between two images is discussed. The simplicity and low cost of this method make it particularly suitable for the full-view white light holographic display of moderate-sized objects.     

Analysis and elimination of boundary reflections in transmission holograms

Elimination of reflections which occur at the glass–air interface of holographic plates is an important factor to be taken into account when recording transmission holograms. If these reflections are not eliminated, unwanted secondary gratings are stored due to interference of the object and reference beams with the beams reflected at the interface. This not only gives rise to an anti-aesthetic effect, but also produces a reduction in diffraction efficiency and an increase in noise. We present the results obtained using a method which eliminates these unwanted reflections. This method, instead of using liquids, makes use of a black self-adhesive PVC masking tape stuck on the glass side of the holographic plate. We carried out a qualitative analysis of the different results obtained for plates with and without black PVC tape and also quantitatively analyzed the effect of the tape on the reflectivity of the plates as well as the density of holographic gratings. The results obtained confirm the applicability of the method described for antihalation reduction and elimination of unwanted reflections that cause interference affecting the quality of the holographic image.     

Driving and analysis of micro-objects by digital holographic microscope in microfluidics

We propose an optical configuration in which floating particles in a microfluidic chamber can be characterized by an interference microscopy configuration to obtain quantitative phase-contrast maps. The configuration is simply made by two laser beams from the same laser source. One beam provides the optical forces for driving the particle along appropriate paths, but at same time works as the object illumination beam in the holographic microscope. The second beam plays the role of the reference beam, allowing recording of an interference fringe pattern (i.e., the digital hologram) in an out-of-focus image plane. The system and method are illustrated and experimental results are offered for polymeric particles as well as for in vitro cells with the aim to demonstrate the approach.     

高质量全息光栅的制作

全息光栅由感光版记录高斯光束干涉条纹制得 ,干涉条纹的不等宽性降低了光栅品质。制取高质量全息光栅的关键是要用均匀平面波作光源。在分析干涉区内光强分布的基础上 ,给出了制作等周期正弦全息光栅的两种方法 :限制曝光区大小的方法和高斯光束强度均匀化的方法。     

Holographic grating recorded by He–Ne laser operating at 632.8 nm in polymer film containing push–pull azo dye

Holographic gratings were optically recorded by two beams from a He–Ne laser operating at 632.8 nm in poly (methyl methacrylate) (PMMA) film containing push–pull azo dye. The holographic characteristics of the recorded gratings were dependent on the polarization direction of the recording beams and the relationship between the diffractive signals and the power density of recording beams was investigated. The formation of holographic gratings accompanied by 532 nm (double-frequency of Nd:YAG laser) irradiation was studied in detail. It was found that the effect of 532 nm laser to the holographic grating lay in two aspects. The acceleration effect of 532 nm laser to the formation of holographic grating is predominant when the power density of 532 nm laser is low. While at relatively high power density of 532 nm laser, the erasure is the main factor to the holographic grating. Moreover, the holographic grating was probed by 532 nm laser at low power density and the dependence of the first order diffractive signal on the recording beam power density was also presented.     

Tilted and axis-shift Lloyd's mirror system for recording low-density and large-area holographic grating

It is difficult to record holographic gratings of low density (<100 lines/mm) and large area simultaneously using traditional holographic system. In order to produce both low-density and large-area holographic gratings, a tilted and axis-shift (TAS) Lloyd's mirror system was designed for recording such holographic gratings. The recording area will increase largely especially for gratings of low density, by setting the angle between the Lloyd's mirror and the substrate larger than 90°, and meanwhile, by enlarging the intersection angle of incident light and mirror surface. Insuring the projected area onto the substrate by reflex equal to the incident area directly onto the substrate, the optical axis was shifted to realize the maximization of utilization of interference area. The contrast of fringe pattern was analyzed by the coherence for the laser beam in the space and time scale. The TAS Lloyd's mirror system for 60 lines/mm grating in the contrast of 0.8 was optimized, and as a result, the interference area was increased by about 150 times comparing to the traditional Lloyd's mirror system using the Lloyd's mirror of same dimensions.     

用全息相衬显微术对CdTe晶体生长的研究

本文首次探讨并应用全息相衬显微术来研究晶体的高温气相生长动力学.在晶体生长、溶解及不同过饱和度下,观测并记录了CdTe晶体界面的真实扩散层及变化规律,并结合扩散层模型给予了讨论.摸索了提高像质及再现象分辨率的条件.     

菌紫质高密度偏振全息光数据存储实验研究

实验研究了基因改性菌紫质BR_D96N薄膜在不同偏振光记录下的全息存储特性，比较了不同 偏振态记录光和读出光对衍射像光强及信噪比的影响. 实验结果表明，与其他偏振全息记录 相比，正交圆偏振光记录可实现衍射光偏振状态与散射噪声偏振状态的分离，得到高信噪比 的衍射像，同时还具有高的衍射效率. 以 He_Ne 激光器（633nm，3mW）为记录和读出光源 ，用空间光调制器作为数据输入元件，CCD作为数据读出器件，采用傅里叶变换全息记录的 方法，在 BR_D96N 薄膜样品60μm×42μm的面积上进行了正交圆偏振全息数据存储，达到 了2×10⁸bit/cm²的存储面密度，并实现了编码数据的无误读出与 还原. 关键词： 菌紫质 偏振全息 光致变色 光致各向异性 高密度光存储     

Fabrication and characterization of poly(methyl methacrylate) photopolymer doped with 9,10-phenanthrenequinone (PQ) based derivatives for volume holographic data storage

We present our studies on the photopolymer of poly(methyl methacrylate) (PMMA) doped with 9,10-phenanthrenequinone based derivatives for volume holographic storage. By introducing different functional groups on the side-chain of 9,10-phenanthrenequinone molecule, the holographic characteristics of the material can be modified. The photoreaction involved with the holographic recording in the samples was investigated by measuring UV-Vis absorption spectrum and mass spectrum. The experimental results show that the similar behaviors were exhibited in these photopolymers. It is found that phase hologram recording in our PQ derivatives doped PMMA photopolymer involves a structure change of the quinone based molecule, which induces a strong change of the refractive index. Experimental characterizations on holographic data storage, including material sensitivity, dynamic range (M#) and bit-error-rate have been performed. We found that, by selecting appropriate functional groups, an improvement in sensitivity and M# for holographic data storage can be achieved.     

Dynamic and quantitative phase-contrast imaging of living cells under simulated zero gravity by digital holographic microscopy and superconducting magnet

The experiment of dynamic and quantitative phase-contrast imaging of living cells in simulated zero gravity environment were performed by using digital holographic microscopy (DHM) combined with a superconducting magnet (SM). The SM with large gradient high magnetic field was used to simulate zero gravity by levitating biological living samples. The proposed DHM system provided highly efficient and versatile means for dynamically and quantitatively phase-contrast imaging MC3T3-E1 cells. To our knowledge, the phase images of living cells undergoing modifications and division under simulated zero gravity were firstly obtained by using DHM-SM prototype.     

杂环偶氮染料薄膜的全息光存储

采用含杂原子的偶氮染料TADEB、DMTAM、DMTAA和DMTAMB掺杂高分子聚合物PMMA制成薄膜,利用四波混频全息光路系统,研究了它们的全息光存储性质。实验结果显示DMTAA样品的衍射效率最高,可达到22%,是一种存储性能较为优良的永久性全息光存储介质材料。     

Reconstruction resolution enhancement of EPISM based holographic stereogram with hogel spatial multiplexing

We investigate how the splicing mode of a holographic element (hogel) affects the reconstruction of a 3D scene to improve the reconstruction resolution of a holographic stereogram fabricated using the effective perspective image segmentation and mosaicking method (EPISM). First, the effect of hogel spatial multiplexing on holographic recording and reconstruction is studied based on the mechanism of recording interference fringes in the holographic recording medium. Second, combined with the influence of multiple exposures on the hologram's diffraction efficiency, the diffraction efficiency of the holographic stereogram is analyzed in the spatial multiplexing mode. The holographic stereogram is then regarded as a special optical imaging system. The theory of spatial bandwidth product is adopted to describe the comprehensive resolution of the holographic stereogram, which explains why hogel spatial multiplexing can significantly improve the reconstruction resolution of a holographic stereogram. Compared with the traditional printing method under the same parameters in optical experiments, hogel spatial multiplexing has a lower diffraction efficiency but a higher quality of reconstructed image, consistent with the theoretical analysis.     

Phase-contrast volume holographic imaging system

A phase-contrast volume holographic imaging system for three-dimensional contrast enhancement is presented. The system utilizes a spatial filter placed on a conjugate plane to the volume holographic pupil to simultaneously enhance weak phase information at different depths within an object. The proposed system was validated with experimental image data obtained in mouse colon samples and quantitative measurements of modulation transfer function as well.     

Study of near-infrared nonvolatile two-center holographic recording in LiNbO3:Fe:Rh crystal

The near-infrared nonvolatile holographic recording has been realized in a doubly doped LiNbO₃:Fe:Rh crystal by the traditional two-center holographic recording scheme, for the first time. The recording performance of this crystal has been investigated by recording with 633 nm red light, 752 nm red light and 799 nm near-infrared light and sensitizing with 405 nm purple light. The experimental results show that, co-doped with Fe and Rh, the near-infrared absorption and the photovoltaic coefficient of shallow trap Fe are enhanced in this LiNbO₃:Fe:Rh crystal, compared with other doubly doped LiNbO₃ crystals such as LiNbO₃:Fe:Mn. It is also found that the sensitizing light intensity affects the near-infrared recording sensitivity in a different way than two-center holographic recording with shorter wavelength, and the origin of experimental results is analyzed.     

On the holographic simulation of non-circular zone plates

New methods involving the manipulation of fundamental wavefronts (e.g., plane and spherical) with simple optical components such as pinholes and spherical lenses have been developed for the fabrication of elliptic, hyperbolic and conical holographic zone plates. Also parabolic zone plates by holographic techniques have been obtained for the first time. The performance behaviour of these zone plates has been studied. Further a phenomenological explanation is offered for the observed improved fringe contrast obtained with a spherical reference wave. An erratum to this article is available at .