Off-axis Holographic Zone Plates Recorded and Reconstructed by Cylindrical Wavefronts

Theoretical aspects of off-axis holographic zone plate recording using two cylindrical waves, with arbitrary angled focal lines, and replay of such holograms with a cylindrical or spherical wave are discussed in the narrow-beam approximation. Expressions for the distances and orientations of focal lines of generally reconstructed astigmatic beams are given, and conditions for obtaining spherical waves are analysed. The results have been verified by experiments using photographic emulsion (Agfa-Gevaert Holotest 10E56 plates) as the recording material. In particular, experimentally obtained parameters of the reconstructed astigmatic beam and the spherical wave are found to be in good agreement with theoretical results.     

Ebert-Fastie型双层结构平面全息光栅双单色仪的光学设计

为满足空间紫外遥感高精度光谱辐射测量工作的要求,设计了一种Ebert-Fastie 型双层结构平面全息光栅双单色仪,由球面准直聚光镜、平面和屋脊转向镜、平面全息光栅及入射、出射和中间狭缝组成,扫描波长范围160 ～400 nm .这种双层结构的特点在于两块完全相同的平面全息光栅安装在同一转轴上做到同轴转动,不但把机构基本上简化为一个单色仪的结构,而且确保了两块光栅同步地进行光谱扫描,色散相加,光谱分辨率小于0.15 nm .此外,前后两单色系统被隔成基本封闭的腔体,用来割断两单色系统杂散光之间的相互影响,抑制整个系统的杂散光,整个系统的杂散光水平可达10 -6 ,满足空间紫外遥感高精度光谱辐射测量的要求.     

Collinear technology for a holographic versatile disk

A novel reading and writing technology for a holographic versatile disk (HVD) system called collinear technology is developed. With this method a two-dimensional data page can be recorded as volumetric holograms generated by a reference beam and a signal beam that are bundled on the same axis and that are irradiated on the recording medium through a single objective lens. The multiplex recording and reconstruction process is demonstrated, and it is shown that the optical configuration and the dichroic medium disk structure are suitable for a compact system. With the HVD's special structure, the system can use a servo to focus, track, and locate the reading and writing addresses. A unique selectable-capacity recording format of a HVD and its standardization activity are also introduced. This method willenable us to construct a small HVD system with CD and DVD upper compatibilities.     

Self-focusing hidden bar code

A new type of diffractive optical bar code produced by computer-generated holographic technology is proposed. The message in the proposed bar code is hidden in the diffracted light of the bar code element and can be read from the first diffraction order. In contrast to the conventional hidden bar code, which needs a lens to focus the diffracted light, the proposed hidden bar code has a property of self-focusing. This self-focusing ability is achieved by modulating a function of the Fresnel zone plate into the bar code format. Consequently, the read-out process for the information in this hidden bar code avoids the use of a lens. Experiments have shown the feasibility of the proposed bar code and confirmed that it can perform better than the conventional hidden bar code.     

Collinear holography

A novel reading and writing technology for a holographic storage system called collinear holography is developed. With this method, two-dimensional page data can be recorded as volumetric holograms generated by a reference beam and a signal beam that are bundled on the same axis and irradiated on the recording medium through a single objective lens. The multiplex recording and reconstructing process is demonstrated, and it is presented that optical configuration and the dichroic media disk structure are suitable for a compact system. This method enables us to construct a small volumetric optical disk storage system with CD and DVD upper compatibility.     

Analysis of slitless holographic spectrometers implemented by spherical beam volume holograms

The analysis of a slitless volume holographic spectrometer is presented in detail. The spectrometer is based on a spherical beam volume hologram followed by a Fourier-transforming lens and a CCD. It is shown that the spectrometer is not sensitive to the incident angle of the input beam for the practical range of applications. A holographic spectrometer based on the conventional implementation is also analyzed, and the results are used to compare the performance of the proposed method with the conventional one. The experimental results are consistent with the theoretical study. It is also shown that the slitless volume holographic spectrometer lumps three elements (the entrance slit, the collimator, and the diffractive element) of the conventional spectrometer into one spherical beam volume hologram. Based on the unique features of the slitless volume holographic spectrometer, we believe it is a good candidate for portable spectroscopy for environmental and biological applications.     

Generalized Bragg selectivity in volume holography

The diffraction efficiency of holographically recorded volume gratings was extensively studied, and it can be accurately predicted as long as the recording wave fronts are simple. The derivation of the diffraction efficiency when complicated wavefronts or images are involved is much more tedious and less explored. In this work we derive operator expressions that can be used to analyze these processes regardless of the shape of the wavefront and the nature of the optical systems through which they propagate. The compact expressions derived are directly applicable to the analysis of volume holographic processes, and the deterioration of the holographic reconstruction quality is derived as a function of the deviations from the recording parameters. The generalized results obtained reduce to the conventional Bragg effect for plane wave recording and reconstruction. Previously unexplored phenomena are discussed and demonstrated through some simple, and practically useful paradigms, including hologram recording and reconstruction in the Fresnel, Fourier transform, and image plane regions, as well as recording with plane and spherical waves. Some prior experimental results are also interpreted mathematically. In subsequent publications the analysis will be explored further to facilitate its application to more complicated architectures.     

Synthetic aperture superresolution with multiple off-axis holograms

An optical setup to achieve superresolution in microscopy using holographic recording is presented. The technique is based on off-axis illumination of the object and a simple optical image processing stage after the imaging system for the interferometric recording process. The superresolution effect can be obtained either in one step by combining a spatial multiplexing process and an incoherent addition of different holograms or it can be implemented sequentially. Each hologram holds the information of each different frequency bandpass of the object spectrum. We have optically implemented the approach for a low-numerical-aperture commercial microscope objective. The system is simple and robust because the holographic interferometric recording setup is done after the imaging lens.     

Recording method for obtaining high-resolution holographic gratings through use of multimode deformable plane mirrors

We propose a new way of recording in which a spherical blank and a deformable mirror are used to obtain high-resolution holographic gratings. The reflection of one of the two laser recording waves upon this mirror provides the deformations necessary to image correction to as much as seventh-order aberrations inclusively.     

Absorption characteristic and nonvolatile holographic recording in LiNbO3:Cr:Cu crystals

The absorption characteristic of lithium niobate crystals doped with chromium and copper (Cr and Cu) is investigated. We find that there are two apparent absorption bands for LiNbO3:Cr:Cu crystal doped with 0.14 wt.% Cr2O3 and 0.011 wt.% CuO; one is around 480 nm, and the other is around 660 nm. With a decrease in the doping composition of Cr and an increase in the doping composition of Cu, no apparent absorption band in the shorter wavelength range exists. The higher the doping level of Cr, the larger the absorbance around 660 nm. Although a 633 nm red light is located in the absorption band around 660 nm, the absorption at 633 nm does not help the photorefractive process; i.e., unlike other doubly doped crystals, for example, LiNbO3:Fe:Mn crystal, a nonvolatile holographic recording can be realized by a 633 nm red light as the recording light and a 390 nm UV light as the sensitizing light. For LiNbO3:Cr:Cu crystals, by changing the recording light from a 633 nm red light to a 514 nm green light, sensitizing with a 390 nm UV light and a 488 nm blue light, respectively, a nonvolatile holographic recording can be realized. Doping the appropriate Cr (for example, NCr = 2.795 x 10(25) m(-3) and NCr/NCu = 1) benefits the improvement of holographic recording properties.     

Visor-display design based on planar holographic optics

A method for designing and recording visor displays based on planar holographic optics is presented. This method can deal with the problem of recording-readout wavelength shift. The display system is composed of two holographic optical elements that are recorded on the same substrate. One element collimates the waves from each data point in the display into a plane wave that is trapped inside the substrate by total internal reflection. The other diffracts the plane waves into the eye of an observer. Because the chromatic dispersion of the first element can be corrected by the dispersion of the second, this configuration is relatively insensitive to source wavelength shifts. The method is illustrated by the design, recording, and testing of a compact holographic doublet visor display. The recording was at a wavelength of 458 nm, and readout was at 633 nm. The results indicate that diffraction-limited performance and relatively low chromatic dispersion over a wide field of view can be obtained.     

Achromatized transmission-type holographic screen for a multiview stereoscopic image system

The main drawback of the use of transmission-type holographic screens is poor color reproduction caused by their high spectral dispersion. For overcoming this drawback, a long, narrow diffusing slit is used as an object when recording the screen. The necessary size and position of the slit relative to the photoplate and to the recording and reconstruction beams are determined by the phase relations of the beams. By use of the slit, holographic screens of 30 cm x 40 cm are recorded with a diverging reference beam and are used to display a multiview full-color stereoscopic image. The images displayed on the screen show no sign of color separation except near the edges of the screen. The image brightness on the screen is high enough that it can be watched in a normally illuminated room.     

Superresolved imaging in digital holography by superposition of tilted wavefronts

A technique based on superresolution by digital holographic microscopic imaging is presented. We used a two dimensional (2-D) vertical-cavity self-emitting laser (VCSEL) array as spherical-wave illumination sources. The method is defined in terms of an incoherent superposition of tilted wavefronts. The tilted spherical wave originating from the 2-D VCSEL elements illuminates the target in transmission mode to obtain a hologram in a Mach-Zehnder interferometer configuration. Superresolved images of the input object above the common lens diffraction limit are generated by sequential recording of the individual holograms and numerical reconstruction of the image with the extended spatial frequency range. We have experimentally tested the approach for a microscope objective with an exact 2-D reconstruction image of the input object. The proposed approach has implementation advantages for applications in biological imaging or the microelectronic industry in which structured targets are being inspected.     

Polarization holographic high-density optical data storage in bacteriorhodopsin film

Optical films containing the genetic variant bacteriorhodopsin BR-D96N were experimentally studied in view of their properties as media for holographic storage. Different polarization recording schemes were tested and compared. The influence of the polarization states of the recording and readout waves on the retrieved diffractive image's intensity and its signal-to-noise ratio were analyzed. The experimental results showed that, compared with the other tested polarization relations during holographic recording, the discrimination between the polarization states of diffracted and scattered light is optimized with orthogonal circular polarization of the recording beams, and thus a high signal-to-noise ratio and a high diffraction efficiency are obtained. Using a He-Ne laser (633 nm, 3 mW) for recording and readout, a spatial light modulator as a data input element, and a 2D-CCD sensor for data capture in a Fourier transform holographic setup, a storage density of 2 x 10(8) bits/cm2 was obtained on a 60 x 42 microm2 area in the BR-D96N film. The readout of encoded binary data was possible with a zero-error rate at the tested storage density.     

Multiple Beam Wedge Plate Lateral Shear Interferometry in Transmission

Abstract

It is shown that a multiple beam wedge plate interferometer can be used in transmission mode to display accurately the lateral aberration curve of a collimating lens. Experimental results showing the sharpened fringes and a comparison with the computed lateral aberration curves are given. Further, for larger shear, some new features are observed; these are explained by considering contributions of higher order terms in the Taylor's series expansion of the path function.     

Optical and Photographic Problems In the Development and Use of an .f/l .0 Streak Camera Transparent to the Ultra-violet

The early stages of the high-voltage spark discharge in air are faintly luminous, most of the emission lying in the ultra-violet. For the purpose of obtaining time-resolved photographs of this growth, a lens consisting of a pair of monocentric spherical mirrors was designed. The system was of aperture f/1 .0 and focal length 2.4 in, and included a rotating-mirror to give an image velocity of O.14 in./μsec. The lens produced an image of spherical curvature of radius 2.4 in. The technique which was developed to produce films moulded to this curvature is described. The image distortion which is introduced by the system in both space and time is calculated. It is shown that relaxation of the film after removal from the camera reduced such errors considerably. Stationary photographs were used to obtain the co-ordinates of the three-dimensional spark track. Techniques for obtaining accurate time measurement and the elimination of perspective effects are described. Some examples of spark photography and quantitative measurements obtained with this camera are presented.     

Self-recording phenomenon in the process of reconstruction from a highly efficient dynamic hologram on azo-dye-colored material with powerful Weigert's effect

The dynamic process of highly efficient holographic recording of two orthogonally circularly polarized plane light waves on the azo-dye-colored gelatin with powerful Weigert's effect is investigated. The investigation has shown that at some ratios of the intensities of the recording waves the self-recording phenomenon during the reconstruction process by the same actinic light (lambda=488.0 nm) is observed, and the diffractive efficiency for the probe light (lambda=632.8 nm) of an already fully recorded hologram increases again almost instantly after blocking one of the recording beams of low intensity. The maximum diffractive efficiency reaches 40%-45% in this case.     

A Contribution to Hologram Imagery

A very simple method for evaluating hologram imagery in a general holographic arrangement with spherical or plane reference and reconstruction waves is proposed. For the hologram imagery approaching aberration-free case the relations providing new possibilities are introduced. The study is not restricted to plane holograms only but one can also study the imaging of objects reconstructed from volume holograms.     

Combinational system of a truncated ball lens and a hyperbolic lens for collimating a highly divergent source

We propose the use of a truncated ball lens in a collimating system to transform a spherical wave from a highly divergent source into a plane wave. The proposed scheme, which incorporates a hyperbolic lens, is discussed, and the overall system is found to have a large acceptance angle and to be free of spherical aberration. Diffraction and polarization effects are neglected, as well as skew rays.     

Imaging and Magnification Properties in Holography

A formula, which is the equivalent of the law of refraction for a single refracting surface, is derived for the holographic case. The second degree aperture terms in the wavefront aberration function are obtained for a general holographic system, no approximation being made for the inclinations of the reference waves in either the recording or the reconstruction. These second degree terms are used to define the location of the image point. It is shown that, where the reconstruction reference wave differs appreciably from that used for the recording of the hologram, the image is not merely magnified or reduced, but is also anamorphotic. Formulae are derived for the azimuths of each of the principal sections and for the two magnifications in these sections. It is then possible to establish the nature of holographic image formation in the general case.