物面单反射镜波前分割三光束全息干涉计量研究

提出了一种用于分析物体三维位移场的全息干涉计量新方法。该方法将一个小平面反射镜贴于被测物体的表面，用三束呈空间分布的发散光波，在干版的三个不同区域或同一部位，记录被测物体的三个独立的双曝光干涉图。这些干涉图被由小平面反射镜运动造成的参考光虚点光源的位移所调制。基于对这种调制的理论分析，导出计算参考光虚点光源和被测物体三维位移的二个线性方程组。     

Acoustical-photorefractive recording of acoustical oscillations

The process whereby acoustic waves are recorded in photorefractive piezoelectric crystals by means of the acoustophotorefractive effect is studied. Expressions are obtained for the electric fields and elastic displacements of the recorded holographic lattice. The kinetics of the recording of monochromatic waves and complex acoustic signals under the action of pulsed uniform illumination is studied. It is shown that in the case when a complex acoustic signal is recorded the signal recorded with short recording times is the derivative of the input signal.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 33–37, July, 1987.     

Hologram recording in glass and direct reconstruction using visible-wavelength laser beam

We propose a method of hologram recording in a glass plate by corona charging. The holographic recording materials used in this study are conventional soda-lime glass and azobenzene polymer film. A Fourier transform hologram on an azobenzene polymer film coated on the glass plate is recorded in the glass plate by corona charging. After removing the polymer film, the hologram recorded in the plate can be reconstructed using a visible-wavelength laser beam. The first-order diffraction efficiency of the hologram at a wavelength of 532 nm is 0.03%; the efficiency depends on the depth of the surface relief structure on the azobenzene polymer film and the corona-charging time. The hologram recorded in the glass plate has high environmental resistance.     

The effect of initial stress on the propagation behavior of SH waves in piezoelectric coupled plates

This study analytically investigates the propagation of shear waves (SH waves) in a coupled plate consisting of a piezoelectric layer and an elastic layer with initial stress. The piezoelectric material is polarized in z-axis direction and perfectly bonded to an elastic layer. The mechanical displacement and electrical potential function are derived for the piezoelectric coupled plates by solving the electromechanical field equations. The effects of the thickness ratio and the initial stress on the dispersion relations and the phase and group velocities are obtained for electrically open and mechanically free situations. The numerical examples are provided to illustrate graphically the variations of the phase and group velocities versus the wave number for the different layers comparatively. It is seen that the phase velocity of SH waves decreases with the increase of the magnitude of the initial compression stress, while it increases with the increase of the magnitude of the initial tensile stress. The initial stress has a great effect on the propagation of SH waves with the decrease of the thickness ratio. This research is theoretically useful for the design of surface acoustic wave (SAW) devices with high performance.     

Characteristics of photopolymer holographic matched filters in a van der Lugt correlator

Parameters of van der Lugt holographic matched filters for phase and amplitude transparencies, including random phase masks, are studied. Conditions for recording such filters in a phase self-developing photopolymer are determined. A significant difference in the recording conditions for the holographic filters for amplitude transparencies and phase masks is demonstrated. The holographic filters for phase masks with a signal-to-noise ratio of 20–40 dB and η from 6 to 70% that are recorded in the photopolymerizable composition seem to be promising for optical pattern recognition.     

The measurement of residual stresses by sandwich holographic interferometry

Sandwich holographic interferometry was first proposed by Prof. N. Abramson in 1974. There are many advantages in using this method. One of its most important virtues is that it can compensate for rigid body displacements between the two exposures and is very convenient in practical operation. The authors have already made a detailed theoretical analysis of in-plane and out-of-plane displacements. This paper describes experimental measurements of the residual stresses in welds, by studying the curvature or the second-order derivative of the fringes of in-plane or out-of-plane displacements, using sandwich holographic interferometry. The stresses are obtained quantitatively, and are verified by an experiment involving measurements of the stresses of a flat plate.     

调制光束全息干涉计量的研究

本文提出了干版运动对记录光束的调制作用及其对全息干涉计量的影响,推导了干版运动调制光束双曝光干涉图的光强分布的数学表达式.在对这种调制干涉条纹的理论研究基础上,提出了被测物体三维位移场的调制光束全息分析法.其中干版的运动用参考物体法确定.     

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.     

Sensitivity and optimization in the determination of deformations by holographic interferometry

The use of a fringe-counting holographic interferometric technique for measuring small superficial displacements can present difficulties in determining the measurement inaccuracy. A useful general method is given here for the analysis of errors in displacement measurements. The optimum number and type of observation directions are determined and correspond to counting in the four semi-diagonals of the holographic plate. The technique, as applied to skull experiments, makes it possible to measure directly displacements of up to 20 μm, in the object plane parallel to the holographic plate. The associated errors range from 0.1–0.3 μm, for a counting inaccuracy of of a fringe and increments of traction of 100 g to 1 kg of force.     

一种制作投影灰度正弦光栅的新方法

针对传统方法难以制作结构光三维投影测量设备的灰度正弦光栅元件,并以Ronchi光栅代替从而影响测量准确度,提出了一种制作灰度按正弦分布的光栅模板的新方法.通过对银盐全息干板透过率特性曲线的理论分析,指出在对比度为一的正弦干涉条纹下曝光不能得到线性记录和变换的原因,并提出了采用均匀非相干光预曝光提供偏置点来实现线性记录的新方法.实验表明,采用空间滤波法能够获得对称双光束正弦干涉条纹记录,并准确控制正弦干涉条纹曝光在干板的线性区域,可以达到线性记录并获得尽可能高的反衬度.     

Piezoelastic vibrations of composite Reissner-Mindlin-type plates

Linear vibrations of Reissner-Mindlin-type composite plates in the presence of piezoelectric eigenstrains are studied. Piezoelectric eigenstrains are produced by applying electrical loads to piezoelectric layers embedded in or attached to substrate layers. The influence of the mechanical field upon the electric field is taken into account in the modelling, ending up with electro-mechanically coupled field equations and boundary conditions, which describe the mechanical and the electrical dynamic response of the plate.The mechanical displacements are approximated by means of the kinematic hypothesis of Hencky. The electric potential distribution is assumed to be composed of a superposition of a linear and a parabolic distribution in the thickness direction. The linear part accounts for the electric potential difference between the electrodes of the totally electroded piezoelectric layers. The parabolic part is considered in order to take into account the influence of the mechanical field upon the electric potential by means of the direct piezoelectric effect. A weak two-dimensional formulation of the three-dimensional field equations is obtained by utilizing mechanical and electrical variational principles. This formulation is characterized by resultants of stress and electric displacement. The electro-mechanically coupled behaviour comes into play by means of the constitutive relations. In case the electric potential difference is not prescribed, it can be calculated from a relation, which connects the total electric charge and the electric potential difference to each other. Because this relation is obtained from the Gauss law of electrostatics, requiring integration with respect to the area of the electrode, non-local constitutive relations for the plate are found. The non-local constitutive relations bring a new aspect into the theory of plates. An analysis for the practically interesting one-dimensional case of composite, piezoelectric plates in cylindrical motion completes the paper.     

Spectral selectivity of holographic mirrors recorded in an attenuating medium

Numerical simulation of the optical properties of unslanted reflection holographic gratings (holographic mirrors) is made by the characteristic matrix method. The holograms are recorded in an attenuating medium but the reconstruction is that of pure phase structures in which the refractive index depends exponentially on the exposure. The dependence of the hologram spectral selectivity on medium absorption, amplitude ratio of the two interference waves and recording linearity is studied.     

Minute displacement and strain analysis using lensless Fourier transformed holographic interferometry

An optical system for lensless Fourier transformed holographic interferometry is constructed to enable the measurement of minute displacements from nanometers to micrometers scale and to obtain corresponding strain distributions using a CCD camera with poor spatial resolution. Since a Fourier spectrum of an object beam is recorded on a hologram in this technique, the image reconstruction is easily performed with a single pass of 2-D fast Fourier transformation. Then, the map of the phase difference over the whole field is obtained by comparing two images before and after deformation. A suitable and effective unwrapping process is, however, inevitably required since the phase difference distribution is wrapped from −π to π in this technique. For phase unwrapping, the maximum spanning tree method is adopted here, which seeks a spanning tree that maximizes overall edge weights given by the cross amplitude. In-plane and out-of-plane displacements are obtained separately from the phase difference distributions at one's request. Moreover, in-plain strain is easily calculated from the in-plane displacement distribution.     

双掺杂铌酸锂晶体中体全息记录的振荡特性研究

分析了双中心记录初始阶段振荡现象的产生机制,研究了晶体掺杂浓度和记录光与UV光的束比对记录初期阶段振荡特性的影响.结果表明,振荡现象可以归因于记录介质双能级中心深浅能级电子数平衡分布的改变.在浅能级掺杂浓度较小的晶体中记录时,振荡强度较大;记录光与UV门光束的光束比越大,振荡持续时间越短.     

Content-addressable Holographic Digital Data Storage Based on Hybrid Ternary Modulation with a Twisted-Nematic Liquid-Crystal Spatial Light Modulator

We propose and demonstrate the use of hybrid ternary modulated digital pages for content-addressable holographic data storage. Display of binary data pages with equal number of ZEROs and ONEs by modulating both amplitude and phase of beams using twisted-nematic liquid crystal spatial light modulator, reduces strong de component and produces a more homogeneous spectral distribution at the recording plane. This technique facilitates better recording of all spatial frequencies, thus improving the discrimination capability of a content-addressable memory. Hence we get better results in associative recall in a holographic memory system, with very low number of false hits. An important advantage of the hybrid ternary modulation over pure phase data pages is that it offers a dark state for coding the undesired portion of the SLM while the search argument is small. The unique orientation of quarter wave plate and the analyzer blocks the light transmitted from OFF pixels leading to near total removal of dark signals. This in turn improves the system performance and reduces the number of false hits when the size of the search argument is small. Our experimental results show good discrimination capability and signal-to-noise ratio for a hybrid ternary modulation based content addressable memory.     

Some investigations in holographic microscopic interferometry with respect to the estimation of stress and strain in micro-opto-electro-mechanical systems (MOEMS)

Holographic microscopy with conjugate reconstruction for the interferometric determination of three-dimensional displacement was used for the investigation of the mechanical behaviour of micromechanic and microelectronic components. An experimental set-up for the exposure of the holographic interferograms is described for the application of the spatial heterodyne technique, for the application of phase shifting, and for electro-optic holography. Three holograms for different illumination directions recorded on one holographic plate were reconstructed conjugately, and spatial-heterodyne technique as well as phase-shift technique were used to evaluate the interferograms. Only by conjugated reconstruction, it is possible to obtain a perfectly optimised interferometer for the static evaluation method. The evaluation of interferograms, which are strongly disturbed by speckle noise, can be performed successfully. A comparison of the results of the application of these techniques is given. The influence of the speckle effect on the resolution was investigated.     

Holographic manipulation of nanoparticle distribution morphology in nanoparticle-dispersed photopolymers

We report on experimental verification of mass transfer of nanoparticles during holographic recording in nanoparticle-dispersed photopolymers. Through direct observations of the microscopic structure of recorded holograms as well as optical measurements of the phase shift between the light interference pattern and a recorded hologram we find that holographic exposure causes nanoparticles to be redistributed from bright to dark regions, leading to periodic assembly of nanoparticles and thereby to formation of high-contrast holograms.     

Rainbow holographic camera

A rainbow holographic camera system is presented. The system uses only a single laser beam for recording, so an antivibration arrangement is not required. The slit effect of the rainbow hologram is generated by replication from the slit master plate. Clear three-dimensional images have been sucessfully recorded by the system. The system is also useful for holographic interferometery.     

Higher-order harmonics in bleached silver halide holograms

A large number of plane wave holograms were recorded in Agfa-Gevaert 8E75HD holographic plates, at a wide range of bias exposures and fringe visibilities. The plates were processed by various combinations of developers (AAC, Pyrogallol and Catechol) and bleaching agents (R-9 and EDTA). The phase gratings were studied by phase-contrast microscopy, using a high-power immersion (100×) objective. The phase-contrast photomicrographs were Fourier analysed. Thus, first-, second-, and third-order modulations of the refractive index as a function of bias exposure and visibility of the recording interference pattern could be determined. The ratio of the amplitudes of higher-order modulations to that of the first-order can serve as a measure of the nonlinearity of the holographic recording.     

湍流激励下柔性层贴敷加筋板自噪声的特征机理

为了研究湍流激励下柔性层贴敷加筋板自噪声的特征机理,基于湍流边界层壁面脉动压力功率谱模型、周期加筋板弯曲运动方程和固体波动方程以及力平衡与位移连续边界条件,建立了湍流边界层壁面脉动压力激励下柔性层贴敷单向周期加筋板的振动及内噪声物理模型。研究发现:橡胶外贴时对湍流激励下壳板的减振降噪主要依靠橡胶的厚度模态振动。无筋时,橡胶层外贴板较无橡胶贴敷板,主要降低湍流脉动压力的水动力学成分所致结构自噪声,距壳板0.05m时,声压降幅小于3 dB,橡胶外贴加筋板相对于加筋板,对湍流激励结构自噪声的降低基本涵盖整个波数域,距壳板0.7 m处,声压降幅仍然在20 dB左右。肋骨横截面高度或宽度每增大1倍,壳板肋骨处加速度自功率谱级降低3 dB,非肋骨处加速度及板内侧声压自功率谱则基本不变,肋骨间距改变对壳板加速度响应及板内侧声压自功率谱级皆无显著影响。