Vibration measurement by vibrating-plate holograms

If a hologram of a vibrating object is recorded on a photographic plate which vibrates synchronously with the object, the reconstructed image produces equi-amplitude fringes of the object vibration, the amplitude of which is reduced by a constant determined from the amplitude of the plate vibration. This phenomenon can be used as a method to extend the measurable range of vibration amplitudes, and some experimental results are shown.     

Detection of small displacements with the help of an auxiliary diffuser

We propose here a method of detection of small displacements, in which the speckled image of the object is modulated by an additional speckle. Due to this additional speckle, the Fourier transform fringes of the doubly-exposed photographic plate undergo a diminution of contrast when the object suffers a displacement.     

Double exposure, multiple-field particle image velocimetry for turbulent probability density

A particle image velocimeter method is described in which double exposed fields of particles moving in a two-dimensional slice of a steady turbulent flow are photographed repeatedly to build up a statistical ensemble of flow field realizations on a single photographic plate. Each interrogation spot on the plate contains a sample of the probability density function of the two components of velocity that lie in the photographic object plane, assuming paraxial photography. Theory is developed showing how this sample can be measured by two-dimensional spatial correlation analysis, followed by deconvolution to remove the effects of finite particle image size. The probability density measurements are biased inherently against large velocities, but these effects can be minimized and/or corrected.     

Measurements of axial displacements undergone by a diffusing object in speckle photography

The speckles of the image plane of an object are both radially shifted and decorrelated when the object is axially translated through an amount ?. We demonstrate that this radial shift, which is related to the position of the pupil of the optical system, disappears when the pupil lies in the back focal plane of the imaging lens. However, if the irradiance of the image plane is twice recorded on a photographic plate which is laterally shifted through ζ_H between the exposures, the minimum value of the contrast of the Fourier fringes exhibited by the plate after processing, gives the value of ? if ? is less than a particular value, ?_M which will be defined. Also we propose a new speckle measurement method in which the fringes are automatically removed when ? is greater than ?_M. We record the image of the object illuminated in convergent light through an amplitude diffuser placed in the Fourier plane of the object. The mean speckle speckle size of the diffuser is equal to the mean size of the speckles generated by the object in its Fourier plane.     

Real-time seeing through moving fog

Holographic observations through moving fog yield better images than ordinary photography does. Previously, holography through fog suffered from a time delay caused by the photographic development process of the hologram plate. Now we use the cathode of a TV tube for recording temporarily an image plane hologram of the object. This hologram is reconstructed at TV speed by means of an electronic high pass filter. The reconstructed image on the monitor is far superior over an ordinary image taken through the same fog.     

Determination de rugosite par correlation des speckles dans l'image de la surface diffusante

Two speckle patterns are recorded on a photographic plate which lies in the image plane of a rough surface. The angle of incidence of the parallel beam illuminating the object is slightly varied between the two exposures. It is possible to localize and measure different roughness of the surface by observing suitably the photographic plate. We discuss the experimental setup and the effects of the optical system.     

Detection of small displacements of diffuse objects illuminated by a speckle pattern

The detection of axial displacements of an object imaged with a laser beam on to a photographic plate is not easy because the aperture of the imaging system is not generally large and the variation of its impulse response with the defect of focus is then relatively slow. We propose here a double-exposure method in which the object is illuminated under a large angle of incidence θ by a random beam which is generated by a laser-illuminated ground glass. After the first exposure, the object undergoes an axial translation ? and the photographic plate is laterally displaced. ? is small and we can assume that this axial translation results only in a lateral displacement ? tg θ of the incident amplitude from the ground glass. Under these conditions, the two intensity distributions recorded by the photographic plate are no more identical and the contrast of the Young's fringes observed in the Fourier plane of the photographic plate is a decreasing function of ?.     

Circular carrier-frequency photography for observing phase objects

A circular grating is photographed through a phase object which deforms the image of the grating lines. By super-imposing these deformed lines with a master grating on photographic film, moiré patterns are observed. These patterns are interpreted as fringes of constant radial derivative.     

高速摄影测量技术在飞机外挂物投放运动分析中的应用

本文叙述了某新型飞机在设计研制过程中,需要对翼下挂架投放机构进行运动分析的课题,利用高速摄影测量技术进行全过程的实测分析。文章叙述了摄影测试的原理、方法。着重讨论了摄影测量中一向被人们所忽视的场地测量与校验。认为等待型摄影测量中,摄影比例尺的精度除与所用设备的精度有关外,还与场地测量精度有关。在动态摄影测量中,测试方法、测量场地布置与控制点的建立,以及时间量的正确量测,对摄影测试精度有很大影响。     

模糊和散射对闪光照相边界检测的影响

借助蒙特卡罗方法模拟闪光照相过程,研究了模糊和散射因素对边界检测的影响。结果表明：模糊与边界退化量的变化关系依赖于相邻飞层的材料、密度和尺寸;相同客体结构下,模糊越大,边界退化量也越大;客体结构不同,相同模糊下的边界退化量也不同;散直比越大,散射对边界检测结果的影响也越大,当散直比大于50时,散射引起的边界检测误差超过1个像素。     

相对孔径与曝光量

本文对照相物镜相对孔径的定义、光圈数、像面照度、像面曝光量以及它们之间的关系进行了讨论。     

Longitudinal distortion in images reconstructed by reflection holograms

Reflection holograms recorded on photographic materials usually reconstruct an image at a shorter wavelength than that at which they were recorded. As a result, the lateral and longitudinal magnifications of the reconstructed image are not the same and the image appears distorted. It is shown that this distortion can be minimized by a proper choice of the recording geometry. The residual aberrations of the image are discussed.     

照相物镜移植应用的研究

对于用逐步修改法设计光学系统,初始结构的选择是重要环节。除在典型形式中寻求初始结构外,也可以借鉴其它系统的光学结构进行相似创新。照相物镜移植应用指的是不同系统物镜因成像功能相似,故可实施光学结构的优化替代。本文研究了各种物镜成像功能的相似性,不同系统大孔径、大视场物镜光学特性的边缘性;根据像差理论阐明了照相物镜是大孔径、大视场系统理想的结构替代源;结合照相物镜丰富的光学结构资源的实际情况,指出移植应用是可行的。将照相物镜移植应用于其它系统大孔径、大视场物镜设计中,生产出与照相物镜结构相似、像质优良的镜头。实践证明了移植应用的实用性与可操作性。     

Enhancement on the generation of sampled phase-only holograms

Past research has demonstrated that if the intensity image of an object is uniformly down-sampled and converted into a Fresnel hologram, the phase component alone will be sufficient to reconstruct the source image. However,due to down-sampling, the edge and line patterns are degraded heavily. In this Letter, we propose an enhancement on the parent method by incorporating an adaptive down-sampling lattice. A hologram generated with our proposed method, which is referred to as the edge-enhanced sampled phase-only hologram, preserves favorable visual quality on both the shaded regions as well as the edge patterns of the object image.     

Speckle-pattern interferometry applied to the study of phase objects

If a speckle pattern is photographed through a phase object, the individual speckles are displaced over varying distances depending upon the phase irregularities in the object. A double exposure is made, the object being present during one of the two exposures only. When the processed photographic plate is observed through an aperture stop in the Fourier transform plane, interference fringes representing contours of the optical path gradient are obtained. The sensitivity of the method and the direction along which the gradient is measured can be varied by modifying, respectively, the distance of the Fourier-plane aperture from the optical axis and its azimuth.     

Detection of coloured tracks of heavy ion particles using photographic colour film

A photographic colour film, which was exposed to heavy ions, reveals a coloured dye image of the ion tracks. Since the colour film consists of several layers and different colours appear on each layer, three-dimensional information on the tracks in the layers can be obtained by the colour image. Previously, we have reported the method for which the tracks in different colours represented differences of track depth and we also discussed the disadvantages of using commercial colour films. Here we present the procedure for a self-made photographic coating and the development formula which can overcome the disadvantages.     

Multiplexing with an extended broad-band source

Carrier-frequency photography in incoherent light can be employed for storing a number of real amplitude objects on a single photographic plate. The objects are placed, successively in contact with a grid and a frequency-plane mask selects two different spectral orders for each object. Different intensity distributions modulate different fringe systems in the image plane and can be retrieved with appropriate filters.     

Observation of a phase object using carrier-frequency photography

A Ronch ruling is photographed through a phase object which produces deformations in the grating lines. The superposition of the straight rulings and the deformed ones on the photographic plate gives rise to a moiré pattern which characterises the phase variations of the object.     

Essay Review-Scholarly froth and engineering skeletons

Holography is a two-stage process of photography using coherent light from a laser to illuminate the scene. In the first stage a hologram is formed by combining the light scattered from the object and the direct laser beam on a photographic plate. In the second stage a three-dimensional image is reconstructed without the use of lenses, by directing the laser beam through the hologram. Applications of holography include information storage, recording of images in depth, the use of holograms as optical elements, and as a means of performing precise interferometric measurements on three-dimensional objects of any shape and surface finish.     

Determination des lignes de niveau par double photographie en lumiere coherente

Two images of a rough curved object, illuminated by a coherent parallel beam are recorded on the same photographic plate. The incident beam is slightly tilted between the two exposures. In a suitable filtering set-up we observe the depth contours of the object (parallel to the photographic plate); the experimental limitations are discussed.