一种高衍射效率的偏振全息记录介质的研究

本文研究了一种偶氮染料——明胶体系的偏振全息记录材料的特性,它具有实时记录,可重复使用,衍射效率高(>30%),保存期长,所需阀值激光功率低等特点.此外还研究了衍射效率与偏振状态的关系,给出了详细的研究结果.     

DCG全息元件的简化处理及特性研究

本文提供了重铬酸明胶（ＤＣＧ）的一种简化处理步骤，最高衍射效率和透明度均达９７％，测量和分析了处理后ＤＣＧ光栅的衍射特性，讨论了高质量ＤＣＧ全息元件的应用。     

制作具有预期位相调制度的卤化银乳胶位相型薄全息光栅的研究

提出了一种制作具有预期位相调制度的卤化银乳胶位型薄全息光栅的方法。它通过分析所拍摄的第一张全息光栅的数据来获得最佳曝光参量，从而使继后的拍摄，在同样的实验条件下能获得所预期的位相调制度。文中给出了这方法的理论分析和某些应用。     

一种间接测量相位型全息记录介质折射率调制度的方法

为恰当评价各种相位型全息记录介质的衍射能力及相应的各种处理工艺,本文给出一种利用分光光度计测量介质折射率调制度的原理和方法.     

国产KL全色全息干板感光特性研究

为了用国产KL型全色全息干板制作真彩色反射全息图,对KL全息干板的感光特性进行了实验研究.介绍了实验的光路,化学处理方法,三基色的选择.测试了底片单波长记录的感光特性和波长灵敏度,对三基色波长记录的特性进行了实验和分析,结果表明KL全息干板可用于记录真彩色反射全息图.     

高性能激光全息防伪标识特性参数测量系统

提出了一种高性能激光全息防伪标识参数的检测方法,利用同一束光在分束器分成的反射光和透射光光强度比例恒定的性质,实时探测衍射方向光强和标识入射光强值,通过一维线性扫描实现激光全息防伪标识衍射效率和信噪比的自动测量。实验数据表明：入射光强测量值相对误差不超过0．29％;衍射效率及信噪比的测量值最大相对误差分别不超过0．81％和2．0％,比第一代检测仪采用的方法测量精度提高近一倍。该方法降低了对光源稳定度的要求,大大降低了激光器的成本,有利于测量仪器的推广。     

体全息存储图像的信噪比研究

根据全息存储二值图像的特性,提出了评价重构图像信噪比的方法,并对掺铁铌酸锂晶体中角度复用全息存储图像的信噪比作了详尽的定量研究,包括存储过程中图像信噪比的动态演变,以及页内和页间串扰对重构图像信噪比的影响.测量结果表明,串扰噪声引起的信噪比下降趋势与理论分析一致,图像信噪比的恶化主要是由于相干光学噪声和测量仪器的噪声;实验结果还表明即使在较小的衍射效率下也可获得较好的存储图像信噪比,从而为存储容量和图像质量之间的最佳均衡创造了条件.     

一种全可见光敏感的光致聚合物全息特性研究

制备了一种对整个可见光波段都敏感的光全息存储材料,并研究了该材料的透过率、衍射效率、灵敏度等全息特性.用He-Ne激光器633 nm和Ar+ 激光器514 nm,488 nm,476 nm四种波长的光曝光,材料的饱和衍射效率最大为66%,最小为48%;最高灵敏度为8.06×10－3 cm2/mJ.最高折射率调制度为4.22×10－4.用多波长存储时,不同波长的光可存储多幅全息图,且再现图像清晰.结果表明,该材料是较好的高密度数字全息存储材料.     

Simplified processing and characteristic investigation of DCG holographic elements

In this paper,the simplfied procedures of processing dichromated gelatin(DCG)holographic optical elements(HOE's) are presented.Both diffraction efficiency and transmis-sion of DCG grating made by the procedures have been achieved up to 97%.The diffractioncharacteristics of the DCG gratings are measured and analysed,the applications of DCG grat-ings with high quality are also discussed.     

Investigation of photoelectron temporal characteristics in silver halide microcrystals using the microwave absorption technique

The free photoelectron lifetime reflects to a large extent the latent image formation efficiency and sensitivity of silver halide material. The microwave absorption dielectric-spectrum technique enables measurement of the photoelectron decay process of silver halide emulsion exposed to 35ps laser pulse. For T-grain AgBr emulsion, the relationship between exciting energy and photoelectron action has been obtained, and the influence of iodide dopants on photoelectron lifetime was measured and analysed. The photoelectron lifetime of dye-sensitized AgBr emulsion with tabular grains is shorter than that with cubic grains, and the latent image formation efficiency of the former is higher than the latter.     

On the formation of silver specks in silver halide crystals

This theoretical study summarizes ionic and electronic processes in AgBr crystals and the influence of its results on photographic process. It deals with the importance of surface generated interstitials which Gurney and Mott left untouched because of the non-availability of sufficient data at that time. The magnitude of various parameters,e.g., mean intra-electron-ion distance in a latent image site, the rate of neutralization of Ag⁺ ion with trapped electron and capture cross-section for combination of Ag⁺ ion with the trapped electron, etc. (as desired for understanding the theory of photographic process) are calculated at different temperatures. The results when used in our earlier papers (Singh and Sharma, 1974 and 1975, and Singh 1975) for calculating charged particle track characteristics theoretically were found to give good agreement with the published experimental data (Della Corteet al 1953 and Dyer and Hechman 1967). A model for the mechanism of latent image formation (silver speck) is discussed.     

The fractional ionic character of alkali and silver halide crystals

The fractional ionic character of alkali and silver halide crystals is defined in terms of the deviations from the additivity rule for polarizabilities of ions. The electronic polarizabilities of ions are calculated using an empirical relationship according to which the electronic polarizability of an ion can be assumed to be directly proportional to the cube of its radius. The calculated ionicities indicate that the alkali halides are nearly or more than 90% ionic and silver halides are much less ionic which is also evident from the Phillips ionicity scale.     

Evaluation of holographic emulsion movement using phase difference amplification

A real-time holographic interferometry technique is typically used in the evaluation of aberrations caused by movement of the photographic emulsion. However, this technique is insufficiently accurate when an emulsion, with strain which has been released prior to exposure, is used. A proposed solution is based on the difference amplification method, which uses the higher diffraction orders of a non-linearly recorded hologram.     

Comments on the number of sensitivity centres in silver halide grains

A comment on the number of sensitivity centres in silver halide grains of nuclear emulsions is made and a theory for its evaluation at different temperatures is presented. The results at room temperature agree satisfactorily with assumptions made by various workers.     

Polarization dependence on the holographic recording in spiropyran-doped polymers

We report on the photoinduced anisotropy in the holographic recording in spiropyran doped polymers as a result of the photoizomerization of spiropyran into merocyanine. Photoizomerization is achieved with UV polarized light ( = 355 nm) from the third harmonic of Q-switched Nd:YAG laser. After UV illumination a strong and broad polarization-dependent absorption peak centered 600 nm appears. Absorption holograms were recorded with low power He–Ne lasers with 2.2% output diffraction efficiency for polarization parallel to the polarization of the UV laser. The extremely long lifetime of the merocyanine states (12 days in the dark) and their high resolution makes this material promising as an optical memory element.     

Investigation of the photoelectron decay of silver halide microcrystal

The microwave absorption dielectric spectrum can be used to study the decay process of free photoelectrons and shallow-trapped electrons in semiconductor crystals. The decay curve of free photoelectrons and shallow-trapped electrons of silver halide grains is measured using this technique. The influence of iodide and K_4Fe(CN)_6 shallow electron trap dopants on the photoelectron lifetime of silver halide grains is studied. For the unsensitized cubic AgCl crystals, when the free photoelectron lifetime (FLT) reaches a maximum, the photographic efficiency is optimal. From our analysis, we conclude that FLT is the longest for the cubic AgCl crystals doped with 0.5% iodide at 80% doping position and 1×10^{-6} mol K_4Fe(CN)_6/molAg, whereas, for the highly photosensitized cubic AgBrCl crystals doped with K_4Fe(CN)_6, the photographic efficiency is optimal when the FLT reaches its minimum. The free photoelectron lifetime reaches minimum and the sensitivity of AgBrCl emulsion reaches maximum when the doping position is 30%Ag at K_4Fe(CN)_6 content of 10^{-6}mol/molAg.     

The influence of trapping centres on the photoelectron decay in silver halide

Photoelectron is the foundation of latent image formation, the decay process of photoelectrons is influenced by all kinds of trapping centres in silver halide. By analysing the mechanism of latent image formation it is found that electron trap, hole trap, and one kind of recombination centre where free electron and trapped hole recombine are the main trapping centres in silver halide. Different trapping centres have different influences on the photoelectron behaviour. The effects of all kinds of typical trapping centres on the decay of photoelectrons are systematically investigated by solving the photoelectron decay kinetic equations. The results are in agreement with those obtained in the microwave absorption dielectric spectrum experiment.