Showing papers in "Optics and Lasers in Engineering in 1991"

TL;DR: In this paper, the authors describe a new method for determination of the total phase difference of light waves without interference fringe counting, in which the displacements are determined only by the final values of intensity regardless of the velocity and any prior displacements.

TL;DR: The principle of the Fourier transform method of fringe pattern analysis is described with emphasis on the refinements for high accuracy measurements and the possibility of obtaining the overall accuracy of λ/100 is proved.

TL;DR: In this paper, the problem of a CO 2 -laser beam focusing into a complicated focal domain is considered in detail, and special ray-tracing methods are elaborated to calculate the new analytic functions of diffractive optical elements, called focusators.

TL;DR: In this article, a laser-diode (LD) interferometry based on heterodyne techniques is described, where the wavelength is controlled by the laser injection current and is continuously or stepwise changed to introduce a time-varying phase difference between the two beams of an interferometer with unbalanced optical path lengths.

TL;DR: In this article, the authors used three different illumination geometries around a single imaging system to measure the orthogonal components of vibration amplitude independently and combined these can be combined to determine the three-dimensional amplitude and mode shape.

TL;DR: A new quasi-heterodyne holographic technique is described in which the image is reconstructed using a single beam, and an error compensation scheme is proposed to reduce the effects of random noise.

TL;DR: In this paper, a new method is investigated for synthesis of computer-generated optical elements: focusators that are able to focus the radial-symmetrical laser beam into complex focal contours, in particular into alphanumeric symbols.

TL;DR: The cellular automata method has natural parallelism and can therefore be implemented on an array processor thus rapidly increasing the speed of phase unwrapping, and modifications to the original algorithm allows masking of ‘non-pointlike’ phase inconsistencies automatically, thereby the unwrapped process can be fully computer controlled.

TL;DR: In this article, the optical method of dynamic photoelasticity is used to visualize the load transfer profiles due to explosive loading in granular aggregates, and load transfer functions are developed to predict dynamic contact loads in any systematic or random assembly of grains for any given loading.

TL;DR: An adaptive filter used for enhancement of fringe patterns to restore an ideal cosine distribution from a noisy cosine signal input fringe pattern and enhances the fringe signal to use the full dynamic range of the image detector.

TL;DR: In this paper, an optical method based on speckle-shearing interferometry for the measurement of the slope at any point of an object is presented, where the object under study is illuminated by an expanded laser beam and its image is recorded on a photographic plate placed at the image plane of an image shearing camera.

TL;DR: In this article, the results from two experimental methodologies, photoelasticity aided by digital image processing and precision digital image correlation, are presented for a mixed mode fracture problem.

TL;DR: In this paper, a short history and description of the basic principles of moire interferometry lead to the introduction of a three-mirror, four-beam interferometer.

TL;DR: This article presents an innovative system for interpreting holographic interferograms and other fringe patterns based on the phase-shift method of interpretation that ensures extremely high reliability and transputer technology is used at the same time to enable high-speed interpretation.

TL;DR: In this paper, a simple phase reduction algorithm is used for on-line automated phase measuring profilometry of 3D diffuse objects through a projection moire method and image processing techniques.

TL;DR: In this paper, the authors report the creation of novel computer-generated holographic optical elements by computing diffraction gratings producing a continuous focal pattern in the form of a line and also gratings that have N orders in a row of equal energy.

TL;DR: In this paper, the performance of liquid crystal televisions as spatial light modulators in a variety of optical image processing applications has been investigated in terms of useful working range and the accuracy of displacement measurement.

TL;DR: In this paper, the authors apply the caustics to a number of dynamic problems, including the pseudo-caustic of a Rayleigh wave, the Rayleigh-wave generation during dynamic impact of two elastic bodies, and Rayleighwave interaction with a shallow embedded crack.

TL;DR: An automated processor is introduced which utilises a photorefractive crystal of bismuth silicon oxide to perform this analysis in a fast and cost-effective manner of displacement or velocity data from laser speckle photography or particle image velocimetry transparencies.

TL;DR: In this paper, modans are matched with modal spatial configurations and are able to transform the modal-power distribution into the focal-intensity distribution, which can be used for fiber-optical sensors of microshifts.

TL;DR: Research efforts for interferometric fringe analysis techniques and their applications in Japan are reviewed and theoretical approaches to phase measuring interferometry are described.

TL;DR: In this article, a combination of the reflection grating method and the photogrammetric principle is explained and demonstrated by two examples, and the combination is shown to be useful in quality control and material testing.

TL;DR: In this paper, a new modernization of the Gerchberg-Saxton (GS) iterative algorithm has been suggested with reference to the task of focusing a coherent monochromatic beam into a preset frequency-plane domain with a given intensity distribution.

TL;DR: In this article, the amplitude and phase of a rotational oscillation were measured using a twin photodiode and a lock-in amplifier, and the noise level was 10-13 rad and 10-11 rad, respectively.

TL;DR: Conjugate-wave holographic interferometry is an optical technique which was recently proposed by one of the authors for the measurement, in real time, of in-plane deformation as discussed by the authors.

TL;DR: In this article, the radius of curvature of a spherical surface has been measured by a non-contact interferometric method using Twyman-Green's interferometer without adding the traditional moving focusing lens in one of its arms.

TL;DR: In this paper, the authors examined the performance of three different pulse laser types: YAG, CO 2 and N 2 -laser for the cleaning of glass, and found that a high peak power of about 10 6 J/s and short-pulse duration below 100 ns is necessary in practice.

TL;DR: In this article, the application of holographic interferometry to the measurement of the corrosion rate of aluminium in sodium hydroxide is investigated, and the fabrication of a corrosion cell and the experimental procedure are given.