Comparison of direct,rehalogenating, and solvent bleaching processes with BB-640 plates

Bleaching is one of the key processes in the production of phase holograms with fine grain silver halide emulsions. This step was widely studied for discontinued Kodak, Agfa, and Ilford emulsions, and most of those results have been optimized with small changes for presently available holographic emulsions. A study of the different bleaching techniques with BB-640 holographic emulsions is presented. Some interesting new features found are the high-diffraction efficiencies achieved with direct rehalogenating bleaching and with reversal bleaching, with higher values and better sensitivities than those of classical fixation-free rehalogenating bleaching. In particular, we have found that the highest diffraction efficiency and the lowest scattering is obtained with AAC developer and reversal bleach R-9, with diffraction efficiency values of 82%.     

Silver halide sensitized gelatin holograms in Slavich PFG-01 red-sensitive emulsion

Abstract

Silver halide sensitized gelatin (SHSG) is an interesting technique for the production of holographic optical elements. It combines the high sensitivity of photographic emulsions with the well-known low scattering and high diffraction efficiency corresponding to dichromated gelatin. In this paper we describe SHSG holograms recorded on Slavich PFG-01 emulsions. We will show that real high diffraction efficiencies can be obtained (as high as 93% allowing for reflections) when using this material for recording phase transmission holograms. The influence of the bleach bath temperature and a hardening bath in the processing was studied and the procedure was optimized for these two parameters. Our investigations reveal that PFG-01 emulsion is not only a substitute for Agfa material, but also offers better results, at a moment in which Agfa has stopped its production of holographic material.     

The effect of UV radiation on the properties of diffraction gratings based on dichromated gelatin

Results of experiments on the influence exerted by UV radiation on the height of the surface relief and on the diffraction efficiency of holographic diffraction gratings recorded on dichromated gelatin layers are reported. It is shown that the height of the surface relief substantially increases, which leads to a rise in the diffraction efficiency of the gratings to a value exceeding 25%.     

Silver halide sensitized gelatin process effects in holographic lenses recorded on Slavich PFG-01 plates

In this work we study the feasibility of using silver halide sensitized gelatin based on PFG-01 (Slavich) emulsions to construct uniaxial compound lenses. This processing is able to introduce variations in the thickness and refractive index of the emulsion. We prove that these changes are not sufficient to provide the observed variations in Bragg conditions in the reconstruction and that a shear-type effect must exist to explain the performance of processed emulsions. We study the characteristics of a compound lens, obtaining acceptable image quality, good resolution, and the typical field limitation of volume holographic elements.     

Single-exposure, photorefractive holographic surface contouring with multiwavelength diode lasers

We studied the use of multiwavelength diode lasers for surface profilometry through holographic recording in sillenite Bi12TiO20 crystals. When such lasers are used, the holographic image from single-exposure recordings appears covered with interference fringes providing information on the surface relief of the object. By taking advantage of the narrow interference fringes due to the multiwavelength emission of the laser, we obtained interferograms by holographic recording with two reference beams, which improves the surface analysis by visual inspection and enhances the profilometry sensitivity.     

Study of the pH dependence of diffraction efficiency of phase holograms in dye sensitized dichromated gelatin

Dichromated gelatin is thought to be a good substitute for photographic emulsions in some uses. The results of a systematic study of the effect of the pH of the developer on the diffraction efficiency of volume holographic gratings recorded in dye sensitized dichromated gelatin are presented.     

Holographic Noise Gratings for Analysing and Optimizing Photochemical Processings in Bleached Silver Halide Emulsions

Abstract

Recording noise gratings with single-beam exposures in bleached silver halide emulsions is used as a holographic spectroscopy technique in order to analyse and optimize photochemical processing. In particular, rehalogenating type bleachings are analysed by measuring the transmittance through the recorded and processed holographic plate as a function of the reconstruction angle, the exposure and the concentration of the rehalogenating agent in the bleach bath. The experimental results obtained show us that the analysis of these spurious gratings provides information about the bleaching action during the processing and allows us to identify the optimal concentration of the bleach bath.     

Determination of the refractive index and thickness of holographic silver halide materials by use of polarized reflectances

A method to determine the refractive index and thickness of silver halide emulsions used in holography is presented. The emulsions are in the form of a layer of film deposited on a thick glass plate. The experimental reflectances of p-polarized light are measured as a function of the incident angles, and the values of refractive index, thickness, and extinction coefficient of the emulsion are obtained by using the theoretical equation for reflectance. As examples, five commercial holographic silver halide emulsions are analyzed. The procedure to obtain the measurements and the numerical analysis of the experimental data are simple, and agreement of the calculated reflectances, by use of the thickness and refractive index obtained, with the measured reflectances is satisfactory.     

Polarization Holographic Gratings

Abstract

The photoinduced anisotropy (dichroism and birefringence) in AgCl emulsions is studied as well as the possibility for chemical fixing of this anistropy. A theoretical relation between the diffraction efficiency of amplitude—phase polarization holographic gratings and the photoanisotropy of the recording medium is derived. Based on this relationship an estimation of the properties of the gratings is presented. Polarization holographic gratings with spatial frequencies of 200 to 2000 mm^?1 and diffraction efficiency up to 1·8% are recorded. The gratings are stable, and do not change in time for more than a year.     

Anisotropy of the photoinduced translation diffusion of azo-dyes

Large-amplitude holographic surface relief gratings are optically induced by resonant visible exposure in azobenzene dye-containing polymers. We propose a simple diffusion model accounting for the essential features of surface relief grating formation. It is based on the anisotropic diffusion of azobenzene-dyes in polymer matrices further to their photoinduced trans-cis isomerization cycles. The essential feature of the model is that dye-molecules undergo a 1D-random-walk along their excitation direction. The model accounts for intensity, grating-pitch and polarization dependencies. Understanding of this process appears essential for holography applications. It opens new perspectives associated with optically controlled anisotropic diffusion.     

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.     

Confocal-rainbow volume holographic imaging system

The performance of broadband volume holographic imaging system in terms of depth selectivity is investigated. The mechanism for depth resolution degradation is explained. In order to overcome this resolution degradation, a novel imaging device, the confocal-rainbow volume holographic imaging system, is proposed. Modeling and experimental validation of the performance of this novel imaging system indicates that depth resolution <16 μm is achievable. The lateral resolution of this device is <2.5 μm along a field of view of 300 μm×100 μm.     

Digital holographic microscope for measuring three-dimensional particle distributions and motions

Better understanding of particle-particle and particle-fluid interactions requires accurate 3D measurements of particle distributions and motions. We introduce the application of in-line digital holographic microscopy as a viable tool for measuring distributions of dense micrometer (3.2 microm) and submicrometer (0.75 microm) particles in a liquid solution with large depths of 1-10 mm. By recording a magnified hologram, we obtain a depth of field of approximately 1000 times the object diameter and a reduced depth of focus of approximately 10 particle diameters, both representing substantial improvements compared to a conventional microscope and in-line holography. Quantitative information on depth of field, depth of focus, and axial resolution is provided. We demonstrate that digital holographic microscopy can resolve the locations of several thousand particles and can measure their motions and trajectories using cinematographic holography. A sample trajectory and detailed morphological information of a free-swimming copepod nauplius are presented.     

Depth resolution and displayable depth of a scene in three-dimensional images

The depth resolution and the recordable object depth range, obtainable with parallel, toed-in and sliding aperture camera configurations for multiview image acquisition in the three-dimensional imaging systems, are found by assuming that the camera lens resolution is diffraction limited and the resolution of the recorded image is limited by a pixel pitch of the imaging sensor. The depth resolution for the holographic image is calculated and compared with that of the multiview images for the same parameter values. The influence of the viewer's eye resolution limit on the depth resolution of the multiview images and hologram is also found.     

Dispersive resonators with volume holographic gratings

A dispersive resonator with volume holographic phase gratings for a tunable laser is described. The experimental results showed advantages of these resonators over the analogous devices using blaze-angle reflection relief gratings.     

Fabrication of holographic blazed grating with Fourier synthesis exposure

A simple, direct, and universal fabrication method for holographic blazed gratings is proposed and a 79 lines/mm holographic echelle grating with 4 μm depth quasi-triangular grooves experimentally demonstrated as an example of a blazed grating fabricated directly by Fourier synthesis exposure. With the method, we converted a periodic grating groove profile into the exposure energy spatial distribution on the surface of a photoresist with the response characteristics of the particular photoresist. Then the exposure energy could be decomposed into a series of sinusoidal functions using Fourier series, and realized by superposing a series of two-beam interference patterns. In contrast with mechanically ruled gratings, the fabrication process of holographic gratings is quite quick and low cost, and especially no Rowland ghosts appear in their dispersion spectrum. The reported work will offer a new approach for blazed grating fabrication with a holographic process.     

Optical characterization and applications of a dual-cure photopolymerizable system

The optical response of a photopolymerizable formulation consisting of a bisphenol A epoxy acrylate oligomer, a divinyl ether, and a photoinitiator system containing Rose Bengal was studied by recording holographic gratings. This blend is sensitive to blue-green light. Single- and double-exposure volume phase holograms were recorded. In addition to these examples, surface depth measurements were made by means of a holographic contour technique.     

全息光学元件中编码与象质和衍射效率的关系

以平面波束变换为十字光束的全息光学元件为例，详细分析了ＨＯＥ的相位调制、编码与解主财过程，推导出ＨＯＥ的衍射效率近似解的表达式，计算出近似条件下最佳编码最大刻蚀深度值，并且对该编码方案对ＨＯＥ成象质量的影响进行了分析，得出了分析的结果和结论，同时对衍射效率近似解表达式的误差进行了研究，并给出了分析结果。     

A Holographic Technique Featuring Broad Range Sensitivity to Contour Diffuse Objects

Abstract

We have shown that the performances available from a two-source relief sensing interferometer are improved substantially by combining an innovative way of managing the phase resources inherent in the interferometer. The approach gives rise to the emergence of a flexible and versatile holographic contouring method capable of addressing surfaces of broadly varying depths. Experimental results are presented to support the proposal.     

Photoacoustic holographic imaging of absorbers embedded in silicone

Light absorbing objects embedded in silicone have been imaged using photoacoustic digital holography. The photoacoustic waves were generated using a pulsed Nd:YAG laser, λ=1064 nm, and pulse length=12 ns. When the waves reached the silicone surface, they were measured optically along a line using a scanning laser vibrometer. The acoustic waves were then digitally reconstructed using a holographic algorithm. The laser vibrometer is proven to be sensitive enough to measure the surface velocity due to photoacoustic waves generated from laser pulses with a fluence allowed for human tissue. It is also shown that combining digital holographic reconstructions for different acoustic wavelengths provides images with suppressed noise and improved depth resolution. The objects are imaged at a depth of 16.5 mm with a depth resolution of 0.5 mm.