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Proceedings Volume 0952

Laser Technologies in Industry

Silverio P. Almeida, Luis Miguel Bernardo, Oliverio D.D. Soares
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Proceedings Volume 0952

Laser Technologies in Industry

Silverio P. Almeida, Luis Miguel Bernardo, Oliverio D.D. Soares
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 16 January 1989
Contents: 1 Sessions, 122 Papers, 0 Presentations
Conference: Laser Technologies in Industry 1988
Volume Number: 0952

Table of Contents

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Table of Contents

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Laser Applications In Modern Industries
Anthony J. DeMaria
A short historical review, as well as trends in the laser industry will be be reviewed. The major portion of the paper will summarize specific applications of laser technologies in semiconductor manufacturing, material working, laser radar, electric power cable manufacturing, power recovery in gasoline refineries and nondestructive testing.
Important Factors For Resource Allocation In Applied Research And Development
E. U. Kotte
Competitiveness of modern societies requires optimum allocation of capital, qualified workforce and organizational infrastructure with the connecting link determined by information technology. Human resources of the scientific and technical community can compensate limited resources of other types supported by enhanced information promotion mechanisms in applied research and development. Descriptive features of the problem dimensions are given as a frame of reference, and important factors are reviewed for possible consideration in the fields of technology policy, resource allocation methods and management practices.
Integration And Convergence Of Technologies - A Challenge For Europe
Werner Wobbe
In this paper a long term fusion of microelectronics, photonics and functional materials in basic product components is assumed. Application fields are the opto-electronics in devices of communication technologies, sensors, laser informatics and measurement and control technologies in general. This movement is called the fusion of basic technological families or optomatronics in a study for the FAST Programme of the Commission of the European Communities. The development towards optomatronics is seen in the long term as important as the movement towards mechatronics (the integration of electronics in mechanical products) which occurred since the mid 70's and was put into effect by industrial policies in Japan. It has caused turbulent impacts in mechanical engineering, machine tools, the clock and watch industry and precision engineering in Europe. The same turbulent impacts might arise for industries affected by optomatronic development. This should be counteracted by the appropriate industrial policies.
Optical And Laser Technologies: The Next 25 Years
Roger P. Main
This review presents some major projections respecting the next 25 years of optical, optoelectronic, and laser technologies. The projections given are extrapolations of present knowledge, with emphasis on industrial and manufacturing applications of these technologies.
Electrooptical Technologies Finalized Program Of Italian National Research Council (CNR)
S. Martellucci, A. M. Scheggi
The preliminary study of this program started in 1983 and the authorization to CNR for preparing a feasibility study was given by the Italian Minister for the Scientific and Technological Research on April 4, 1986.
Entrepreneurial Aspects For Industrial Applications Of Laser Technologies
Antonio da Silva Teixeira
Communication gap would be perhaps the key words to identify an important area of difficulties in what concerns the industrial application of technologies.
Eureka : High Power Solid State Laser European Project
Alain Diard
Within the Eureka program, the High Power Solid State Laser project has come to the realization phase. It is devoted to the development of lasers for industrial applications with output powers above 1 kW.
Overview Of Optical Methods In Metrology
Jean Ebbeni
The aim of this paper is not to give a long and tedious description of all the optical methods used in metrology, but to draw some general specific propertters and ideas illustrated by representative applications. Impact of non-linear optics, optical waveguides and holographic optical elements are selected fields for this review.
Non Contact Measuring Machine
Fernando D. Carvalho, Pedro Sebastiao, Bernardo Gorjao Henriques
One of the problems of the production of cables is the measurement of the thickness plastic cover at the production line. If for some reason the thickness of the plastic is smaller than the minimum necessary several meters of cable may be lost. If the problem exists in the middle of a long cable and the default is not detected in time, the loss will be significant. To solve this problem it is possible to use automatic measuring machines which may detect a default as soon as it happens. It is also possible to interact with the production line in order to avoid any losses. In this paper it is presented a non contact measuring machine, developed for this purpose. The machine uses a laser which is scanned through a field of 80 mm. The interruption of the beam gives information about the external dimension of the object. The technical study of the resolution, sensitivity and precision are presented on the paper. Also the hardware solution and the software are presented. The machine has an interface which allows communication with a PC. The PC may receive information from several measuring units and to interact with machines installed at the production line. The prototype is finished and is going to be tested in the industry.
Automatic Machine For Spin Testing
Fernando D. Carvalho, F. Carvalho Rodrigues, Cassiano P. Pais, et al.
One of the bottle necks of the defence industry is the fuze testing. This task must be performed twice for each fuze. It is a 100% test, since all the fuzes must pass two tests. The arming test is performed at an high rotation speed, and it is necessary to guarantee that a minimum diameter is open. The non arming speed must guarantee that a too small aperture has not happened. The usual way to test the fuzes is the visual inspection by experienced operators. This method presents several problems and is always possible to have some faults. To solve this problem, it was developed a special purpose machine to perform this task in a completely automated way. The results of this development are presented in this paper. The optical system which incorporates a laser and the interface with the mechanics of the machine are analysed. The prototype is installed at INDEP and being used for the automatic testing of the fuzes. A description of the optical system and its characteristics are presented in detail.
Laser Scanner For Automatic Storage
Fernando D. Carvalho, Bento A. Correia, Jose M. Rebordao, et al.
The automated magazines are beeing used at industry more and more. One of the problems related with the automation of a Store House is the identification of the products envolved. Already used for stock management, the Bar Codes allows an easy way to identify one product. Applied to automated magazines, the bar codes allows a great variety of items in a small code. In order to be used by the national producers of automated magazines, a devoted laser scanner has been develloped. The Prototype uses an He-Ne laser whose beam scans a field angle of 75 degrees at 16 Hz. The scene reflectivity is transduced by a photodiode into an electrical signal, which is then binarized. This digital signal is the input of the decodifying program. The machine is able to see barcodes and to decode the information. A parallel interface allows the comunication with the central unit, which is responsible for the management of automated magazine.
Interferometric Alignment By A Circular Zone Plate
V. Moreno, M. V. Perez, S. Bara, et al.
A simple method for optical alignment and positioning between two planes by means of a Circular Zone Plate (CZP), is proposed.The first plane is determinated by the zone plate and the other one is related to position of a reflecting surface situated in the forward space of the zone plate. Two points sources are generated by the same zone plate,when it is illuminated by a plane wave, and by several diffracted orders reflected by the reflecting surface.. Interference pattern produced by two spherical waves depend on the relative position of the generating sources. Tilting or axial misalignment between the planes determine the relative position of the two point sources and it yield fringe pattern variation.
Use Of Talbot Interferometry To Measure The Focal Distance Of Refractive/Reflective Imaging Systems
L. M . Bernardo, O. D. D. Soares
A method for the measurement of focal distances of refractive and reflective imaging systems, based on Talbot interferometry, is presented. The experimental conditions and limitations of its application are studied in order to maximize the measurements accuracy.
The Applications Of Laser Beams To Absolute Photodetector Calibration
A. Corrons, J. Campos, A. Pons, et al.
The importance of laser radiation sources in photodetector calibration processes is considered and shown. As an example of that, a recently made work comparing the spectral radiant flux measurement uncertainty of several absolute radiometers is described.
Open Field Phase Measurement Telemeter For Orbital Rendez-Vous
Michel Faup, Francois Hullein
For about four years, collaborating with its industrial and scientific partners, CNES has studied the different types of optical sensors that could help to fulfil an impactless rendez-vous and docking mission between two spatial vehicles moving on a low orbit around the Earth. As a part of that activities, a study realized by Sercel and CNES resulted in the definition of a phase measurement rangefinder able to measure distances from 2 to 500 meters with an accuracy varying from 20 millimeters to 40 millimeters at a rate of 1 Hz. The range and the field of view (+5°) of that instrument together with specific constraints due to spatial environment lead to choose high power (100 mW) current modulated continuous wave laser diode as lightning source for this application. As a matter of fact, the target satellite must keep passive during the mission. Furthermore, the sensor must work in open field to avoid the use of mechanical scanning systems and must be able to deliver a correct information even if the sun is in its field of view so that the rendez-vous scenario is not constrainted. Last, semi-conductor technologies have been preferred because their spatialisation seems to be simpler. Yet, a speckle phenomenon due to the multimode optical fibre onto which the laser diode is connected appears in the field of view. That phenomenon, associated to the dynamic behaviour of the component (spectral drift versus current intensity) prevents the sensor from delivering an homogeneous answer in different points of the field. The phenomenon has been analysed and a solution implying an adapted modulation for the laser diode is proposed. The global sensor principle is described.
Thermal Rectifying Walls: An Interferometric Study
Albino Reis
Energy storage is still an expensive operation in the sense that apart from the store itself, it also includes components for collection, transfer and control of energy flows. An interesting and important improvement would be achieved if the boundary of the store allowed heat transfer between the energy source and the storing material whenever the temperature gradient were favourable and inhibited the heat losses whenever such a gradient were reversed; in other words, the walls of the store would behave as thermal rectifiers. In this work one presents the rectifying effect of a vertical parallelogramic cavity and its application to thermal rectifying walls which could be used in thermal stores. The operation of such walls depends on the enhancement or inhibition of natural convection heat transfer. Using a Mach-Zehnder interferometer front to back ratios of between two and three have been measured.
Natural Convection In A One-Sided Heated Vertical Channel
I. Yalcin Uralcan, Osman F. Genceli
An experimental analysis of natural convection heat transfer in an open-ended vertical channel has been performed, with either water or air in the channel and in the ambient which surrounds the channel. Heating conditions were such that, one of the principal walls-the heated wall-was maintained at a constant uniform temperature (elevated with respect to ambient), while the other wall of the channel was unheated. Temperature distribution and governing heat transfer mechanisms in and out of the channel were observed by holographic interferometry and dimensionless heat transfer correlations were obtained.
Tomographic Presentation Of Temperature Profiles In A Convective Heat Flow By High Resolution Holographic Interferometry
D. Vukicevic, H. Jager, T. Neger, et al.
The aim of these investigations is the development of a new experimental setup, allowing multidirectional analysis of phase objects by high resolution holographic interferometry. With this setup it is possible to obtain interferograms of finite width covering a range of view of 155°. The first tests were performed on a stabilized convective heat flow, since its temperature distribution could be measured with an NTC-detector, providing reference data to check the quality of the tomographic reconstructions. To obtain highest resolution of the interferometric data, the holographic interferograms were evaluated using the formalism of the fast Fourier transformation (FFT). The distributions of the index of refraction were obtained by two commonly used tomographic reconstruction procedures: the convolution method and the algebraic reconstruction technique (ART) showing better results, especially if the projection data are not completely covering 180° of view.
Holographic Evaluation Of Stiffener Configuration On Cover Plate Of Water Box Of An Industrial Heat Exchanger
Chandra Shekar, A. D. Baone, G. Venkata Rao
Holographic interferometry has been utilized for obtaining design information on the cover plate of water boxes of industrial condenser. Experiments for this purpose have been carried out on a properly simulated epoxy model of condenser cover plate, which affords ease of incorporating the various configuration of stiffeners. An extensive numerical data analysis of the interferograms for these configurations has resultted in the evolution of modified stiffener arrangement. The modified stiffener configuration has been tested holographically and found to result in considerable reduction in deformations.
Nondestructive Holographic Testing Of Tubes And Joints
Filipe Morals, Oliverio D. D. Soares
Holographic interferometry has been used to test tubes and joints. Comparative studies of two thermoplastic cameras, combined with image processing, Moire and strobo is described.
Three-Dimensional Displacements By Sandwich Holographic Interferometry
Lingli Wang, Jingtang Ke
In this paper, the mathematical expressions for the three-dimensional displacements of an object by holography are given. The authors derive the general equations for strain and stress using sandwich hologram interferometry. The method has been verified experimentally.
Improvements In Moire-Holographic Gratings For Structural Analysis
Francesco Ginesu, Raffaele Rossi
The authors present a simple method of gratings manufacturing on perspex models, used for structural analysis. The technique is briefly described and the quality and efficiency of grids are discussed. Two simple applications are illustrated.
A Comparison Of The Methods Available For The Evaluation Of Holographic Images
A. Ettemeyer, H. Rottenkolber, J. Schorner
The outstanding advantage of holographic interferometry as a contact-free measuring procedure is that it enables very wide-ranging statements to be made on the behaviour of a component. Measurements are taken simultaneously at several points on the surface of the object, and the result can be assessed visually. For a more precise quantitative analysis, or for automatic evaluation in serial testing, however, evaluation by computer is indispensable. The theoretical basis for this was laid in part several years ago, and suitable equipment in a variety of standard forms has in fact been available on the market for a number of years. This contribution attemps to provide an overall view of the various principles by which holographic interferograms can nowadays be evaluated, together with the areas in which each can best be applied.
Application Of Computer-Aided Evaluation For Holographic Vibration Analysis And Optical Contouring
H. Steinbichler
Holographic interferometry is applied sucessfully in vibration analysis. As the resulting characteristic fringe pattern, the interferograms, are so complicated and can only be evaluated by an expert eye, there is a clear desire for automated evaluation and a lucidly arranged exposition. Therefore, the problem in image processing in interferometry lies in automatically recognizing and evaluating lines, as well as in differentiating the lines from object contours, shadows, etc. This kind of image processing then also makes it possible to evaluate other, non-holographic line systems. The application is not only limited to the automatic evaluation of holographic interferograms, but also in the optical measuring of the form any kind of objects using contour lines projected onto them, in the evaluation of speckle and photoelasticitic diagrams and Moire diagrams.
Optical Non Destructive Testing Of Composite Materials - State Of Art
Jean Ebbeni, Marie-Anne De Smet
Holographic and moire non-destructive testing are well adapted for analysis of composite materials, namely for delamination, cracks inspection, buckling during loading mode and physico-chemical states, because they are quick, cheap and more powerful than other procedures. Some cautions in experimental processing, fringe control and interpretation are nevertheless important to respect particulary for automatic decision of reject or acceptation.
On-Line Fringe Analysis By Real-Time Phase-Shift-Processing
Bernd Breuckmann
This paper presents the concept of a real-time-processor for on-line analysis of fringe patterns which allows the recording of phase shifted fringe patterns and the successive analysis of the image data by the phase shift algorithm in video real-time. In addition, examples will demonstrate the use of the phase-shift-processor in holography, speckle technique, moire- and 3D-measuring techniques.
Digital Phase Stepping Speckle Interferometry
A. A. M. Maas, H. A. Vrooman
A digital speckle interferometric technique for deformation measurement using phase stepping and image processing is presented. The object displacements on a 256*256 grid are calculated by subtracting the phases of the speckle field before and after deformation. Accurate phase measurement is achieved by using reference beam phase stepping and digitizing five interferograms to calculate the phase in each detector point. Application of image processing techniques, for instance new phase-unwrapping algorithms, allow measurement of displacements as small as 1 nm and up to 10 000 nm. Results of measurements of out-of-plane deformation of a circular metal plate are shown.
Modular Holography For Use In Industry
A. Ettemeyer, J. Schorner, H. Rottenkolber, et al.
A new system of holography is presented. This modular testing equipment fulfils the performance requirements for industrial measuring equipment. A holographic camera-head module with the approximate dimensions of a television camera is installed close to or actually on the object to be tested. For holography using a continous wave laser it is necessary only to secure the object to a base-plate mounted on vibration insulators. This is not necessary if pulse holography is used. Because of its small size, the measuring head can also be attached directly to the test object. This largely eliminates the effects of movements of the whole body of the objects. The technical realization of modular holography was made possible by the use of glass fibres. A rigid connection between the laser and the measuring apparatus is no longer necessary. The necessary light for the recording of the hologram is provided by the laser-base module and fed to the measuring head via a glass fibre cable. The hologram recorded by the measuring head is transmitted directly by means of a television camera to the computer-analyzer module, where it is evaluated and presented in user-friendly form. An example from industry is taken to demonstrate the use of the modular holography system.
Industrial Applications Of ESPI
Ole J. Lokberg
ESPI (Electronic Speckle Pattern Interferometry) or TV - holography is a measuring technique very similar to hologram interferometry. However, the technique's speed and stability which is due to video-based recording and electronic reconstruction makes it well suited for vibration and deformation testing within industrial research and testing.
Some New Techniques With Digital Speckle Pattern Interferometry (DSPI)
R. S. Sirohi, A. R. Ganesan, M. P. Kothiyal
Digital Speckle Pattern Interferometry (DSPI) is presented as a real-time technique for a number of applications such as measurement of small displacements, displacement derivatives, contouring, and non-destructive testing. The implementation of DSPI on a commercially available image processing system is described. A method of fringe sharpening in DSPI is also presented.
In-Situ Investigations Of Deformations Of Natural Stones By Electronic Speckle Pattern Interferornetry (ESPI)
G. Gulker, K. Hinsch, C. Holscher, et al.
Due to environmental stresses like weathering and pollution the deterioration of historically valuable monuments increases. A. compact and mobile ESPI system is configurated and described, which allows the investigation of deformations in stones and walls in situ. A first measurement directly at a wall is presented.
Application Of Holography And ESPI Techniques To Earthquake Prediction
Shuzo Takemoto, Taiju Tsuboi
The laser holography and ESPI techniques are used for directly measuring crustal deformation in terms of fringe displacements in the interference pattern. These techniques will be useful to predict occurrences of destructive earthquakes.
Interferometric Studies Of Very Hot Objects By Use Of Tv-Holography (ESPI)
Jan T. Malmo, Ole J. Lokberg
In this paper we outline the problems encountered when doing interferometric testing of very hot objects. We show how the TV-holography (ESPI) system can be used to test objects heated to temperatures close to the melting point of the material. In the experiments we have monitored vibrations, and surface behaviour of objects heated to temperatures close to 3000'C. The tertmratxre limits are apart from microstructure changes and excessive turbulence, set by the accessible laser illumination to suppress the background radiation.
Measuring Rotating Component In-Plane Strain Using Conventional Pulsed ESPI And Optical Fibres
R. W. T. Preater
Pulsed laser ESPI provides a non-contact method of in-plane strain measurement on rotating components. Engineering problems over a wide range of speeds up to 12,500 r.p.m. and tangential velocity of 150 ms-1 may be analysed. Illumination via optical fibres removes the problem of components with limited optical access.
Three-Dimensional Vibration Analysis Using Electronic Speckle Pattern Interferometry (ESPI)
M. C. Shellabear, J . R. Tyrer
ESPI is an established analysis technique, offering the benefits of non-contact, full-field resolution and real-time observation. It has previously been used in many applications for analysis of out-of-plane vibrations and in-plane strains. In this paper it is shown that a combination of out-of-plane and in-plane sensitive ESPI arrangements can be used to measure the vibration amplitude of an object in three independent orthogonal components. These results can then easily be interpreted to determine the full three-dimensional mode shape. The method is demonstrated by observing volume vibrations of a thick hollow cylinder. Experimental results are compared with finite element predictions, enabling the mode shapes to be easily identified and analysed.
Developments In Electronic Speckle Pattern Interferometry For Automotive Vibration Analysis.
Jeremy C. Davies, Clive H. Buckberry, Julian D. C. Jones, et al.
The incorporation of monomode fibre optics into an argon ion powered Electronic Speckle Pattern Interferometer (ESPI) is reported. The system, consisting of an optics assembly linked to the laser and a CCD camera transceiver, flexibly connected by 40m of monomode fibre optic cable to the optics, has been used to analyse the modal behaviour of structures up to 5m X 3m X 2m in size. Phase modulation of the reference beam in order to operate in a heterodyne mode has been implemented using a piezo-electric crystal operating on the monomode fibre. A new mode of operation - sequential time-average subtraction - and the results of a new processing algorithm are also reported. Their implementation enables speckle free, time-average vibration maps to be generated in real-time on large, unstable structures. Example results for a four cylinder power unit, a vehicle body shell component and an engine oil pan are included. In all cases the analysis was conducted in a general workshop environment without the need for vibration isolation facilities.
Visible And Near Infrared HOE's Example Of Geometrical And Chromatic Aberrations In The Case Of An Off-Axis Mirror
Christian Liegeois, Patrice Twardowski
Geometrical and chromatic aberrations of a .specific off-axis holographic mirror are described. This element, basically a collimator, can be made for use in the visible or in the near infrared. A major problem is to avoid or reduce aberrations that result from the shift between the wavelength of reconstruction and recording for a given off-axis reconstruction angle. Holographic recording with an aspheric wave created by a computer generated hologram is presented in an example. The development is made for a collimator in the visible, as used in a Head-Up-Display (HUD), but the given considerations remain valid for an infrared case.
Laser Beam Shaping By Computer Generated Holograms
S. Sahnoune, E. H. Soubari, M. Torzynski, et al.
In this paper, we describe a method and a system to transform a laser intensity gaussian distribution into a uniform distribution. We use computer generated digital holographic filter. We explain the modelisation, the production and the way of use of these filters.
Silver Halide Sensitized Gelatin As A Holographic Storage Medium
A. Fimia, I. Pascaul, A. Belendez
Silver halide sensitized gelatin is one of the most promising techniques for the manufacturing of transmision holographic optical elements. These techniques combine the relatively high sensitivity of photographic material with the low scattering and high light-stability of dichromated gelatin. The influences of the developer and the bleaching in the difraction efficiency and noise is analized starting with Agfa 8E 75 HD plates. According to P. Hariharan,5 we analized the processing steps and this show that the developer action influences on the noise level and the modulation transfer function. The developer of the type PAAP produces better resolution and less noise Ievel than the developer D-19. The bleaching action is related to the difraction efficency and the hardering level of the gelatin. The hardering action is promoted by trivalent chromium ions which are generated in the vicinity of the oxidized silver grains and controled by the ratio concentration to the Cr 13 ions and Br- ions of the bleaching bath. The measurements of the difraction efficiency in the different steps of the processing give us information about the mechanism of hologram formation.
Laser Interferometric Method For The Measurement Of Film Thickness, Using Holographic Optical Components
K. Matsuda, M. Namiki
An interference method for determination of the thickness of thin dielectric films deposited on metal substrates is described. The method uses the variation of multiple-beam interference of light reflected from the sample as the incident angle is changed. The effects of the phase change on reflection at the metal/dielectric interface are shown to be negligible for a MgF2 film deposited on Chromium. A working instrument is described which uses holographic lenses to obtain the large scan angles required with low aberration. The results obtained with this instrument agree well with those obtained using a Talysurf.
Construction Of Holographic Mirrors In Dichromated Gelatin
Ana A. Andrade, Jose M. Rebordao
A method for the construction of high efficiency, narrow spectral and angular bands and low dispersion and absortion holographic mirrors is described. The relevant physical and chemical parameters on the several stages of the production of the hologram regarding the final quality have been studied one by one. Several development temperatures have been carried out. The comparison between those methods is done by the analysis of the final optical mirror properties. Rutherford Backscattering has been used to measure the thickness of the film of gelatin. Some results are presented and the method is discussed.
Coupling Efficiency In A Holocoupler-Optical Fiber System
M. L. Calvo, L. De Pedraza
We present a mathematical model based on the eikonal approximation for the diffraction of a TM wave by an optical fiber with parabolic profile. Optimal conditions for the signal to be totally confined into the fiber have been studied and numerically controlled. The light coupler was a hololens acting as a holocoupler. The total coupling efficiency of the system has been estimated for particular physical parameters.
Software Techniques For The Analysis Of Contour Maps Of Manufactured Components
David R. Burton, Michael J. Lalor
The image processing of contour type fringe patterns to extract coordinate information is well understood. This paper discusses the further processing of this information in order to determine the fundamental geometrical nature of the underlying surface. Particular reference is made to the use of such analysis techniques for industrial inspection of surface form.
Mechanical Design Considerations In Scanning Optical Microscopy
T. Wilson
We review the choice of scanning mechanisms for scanning optical microscopy and discuss the factors which make certain approaches more attractive.
Automatic Surface Analysis Of Projection Interference Fringes
S. P. Almeida, R. W. Wygant, C. D. D. Soares
Projection fringe interferometry techniques were used together with an automatic surface analysis algorithm to construct three-dimensional topographic maps of a nonoptical surface. Parameters determined by the algorithm include: average surface roughness, surface height distribution descriptors and the autocorrelation function. The resolution of the system can be varied from submicron to millimeters in both lateral and vertical directions. Results are presented for a surface analysis of an oxidized roughly cut block of iron. They were found to be in good agreement with measurements obtained via the stylus profilometer method.
Surface Inspection Of Laser Treated Materials Via Three Dimensional Computer Color Contouring
R. W. Wygant, S. P. Almeida, R. J. Churchill, et al.
The inspection of laser treated stainless steel alloy is performed via a microcomputer on-line to a digitizer which records interferograms produced using projection interference techniques. Heating was performed by an high power industrial carbon dioxide laser. Special image processing algorithms were developed to extract the heat variation features from the surrounding background. The results reveal the quality of the laser heat treatment and its effect on different areas of the alloy. Lateral and depth resolutions of the order several microns were achieved. A topological mapping of the treated material is presented as the three dimensional color (or shades of gray) contour of the surface.
Mapping Of Textile Surface Relief
Manuel F. P. C. M. Costa, Jose B. Almeida
We describe a system which is capable of mapping the relief of textile surfaces, by non contact optical means, designed to be used in textile engineering laboratories to study the alterations produced in fabrics by the action of dyes, shock, stress, and so on. The specific nature of these materials precludes the use of conventional profiling systems, which led us to develop a new method with the necessary versatility but reasonably immune to dispersion, diffraction and speckle, phenomena which usually make very difficult the application of optical methods to this situation. The method is based on the horizontal shift of the bright spot on an horizontal surface when this is illuminated with an oblique beam and moved vertically. In order to make the profilometry the sample is swept by an oblique laser beam and the bright spot position is compared with a reference position. The system is thus formed by an HeNe laser focused onto a reference surface (sample support) endowed of bidirectional motion obtained by two stepping motors which are controlled by a 8051 microcomputer that will also control the data acquisition and processing system, and it's forwarding to the working microcomputer. The laser beam incidence angle, the focusing system and the reception objective can be changed to increase the system fickleness.
Eddy Current Nondestructive Evaluation Of Laser Glazed Metallic Surfaces
R. J. Churchill, J. M. Glass, H. P. Groger, et al.
Laser glazing holds great potential for the production of new and improved materials, but there is a need to identify and control the thickness of the glazed layer and to monitor porosity and other defects in the surface layer and adjacent substrate by using nondestructive evaluation techniques. Eddy current methods rely on the interaction of electromagnetic fields with the metallic part under test, which effectively transfers the impedance of the test specimen to the excitation coil so that changes in the test specimen which affect the transferred impedance may be detected by the test coil. This paper addresses the experimental parameters of laser glazing of metallic surfaces, eddy current probe suitability for reliable measurement of thin layers, ranges of operating conditions, sensitivity, speed of response and feasibility of eddy current nondestructive sensors for use in process control.
Physical Backgrounds Of Laser Inspection Of Surface Roughness
H. A. Ferwerda
We present the physical backgrounds of contactless optical inspection of (rough) surfaces by means of scattering of laser light from these surfaces.
Application Of Optical Surface Assessment To Engine Bores
K. J. Stout
Although the advantages of optical techniques for surface assessment have long been appreciated, the inherent limitations of such methods have meant that stylus techniques remain the accepted "standard" for surface assessment. The study of many engineering processes, such as those used for engine bore preparation techniques, have been based on stylus methods, although optical analysis may prove advantageous due to the face that 3D assessment may be achieved much faster. Optical techniques may become more feasible if a detailed comparison of results obtained from the two techniques is carried out, and shows the two methods are comparable. A study of this kind will help to develop optical assessment techniques which, although may initially be limited to specific processes, may prove useful in many production environments. This paper presents a study of established two dimensional models which have been applied to the characterization of the preparation of engine cylinder liners and bores. These models are extended to three dimensions and quantified using a three dimensional stylus measuring system consisting of a computer controlled Talysurf 5. Relocation techniques are then employed on the surfaces used for assessment and the finish is re-assessed using a computer controlled laser measuring system. It is shown that engine preparation techniques may be monitored using optical assessment. Thus, an alternative method of assessing engine preparation is proposed for optically based instruments.
A Laser Rangefinder For Hot Surface Profiling Measurements
Kari Maatta, Juha Kostamovaara, Risto Myllyla
This paper discusses the construction and capabilities of a laser rangefinder system for profiling measurements on hot surfaces (T < 1400°C), especially measurement of the thickness profile of the fire-brick sheathing of a converter. The rangefinder consists of an opto-mechanical measuring head, electronics unit and hand-held computer. Special attention is paid to maximizing the inherently low signal-to-noise ratio typical of measurements of this kind. In addition, an efficient time interval measurement principle is employed which enables rapid determination of a single 3 D point. The measured resolution of the system in a real operating environment is a few millimetres with a measuring time of less than 1 second per measurement point. The accuracy of the system is better than 1 cm in a measurement range of 6 - 17 metres.
Fringe Projection Microscope
J. C.A. Fernandes, Oliverio D. D. Soares
Some techniques for analysis of microtopography of non-optical surfaces using projection of holographically generated interference fringes are described. Digital processing of the obtained images is considered.
Integrated Optical Sensors: State-Of-The-Art And Perspectives
Giancarlo C. Righini, Ahmed Naumaan
The field of optical waveguide sensors is growing fast. Fiber-optic sensors are already on the market, but integrated-optic sensors are still at a research stage, and only few IO devices have been actually developed. Here an overview of the field of integrated optical sensors is presented, and an outline is given of the main characteristics of the integrated optical structures on which most of planar waveguide sensors are based.
Laser And Fiber Optic Sensors: An Overview
M. Brenci, G. Conforti
Different types of sources can be used in fibre optic sensors. In the present work an overview of fiber optic sensor making use of laser as source is made. Typical practical applications are described.
Optical Fibre Sensors - Practice And Possibilities
Brian Culshaw
Fibre optic sensors have attracted a good deal of attention through a period which now extends over 20 years during which a wide range of practically usable devices has been demonstrated. An analysis of these devices indicates that a few appear to be applicable to a diversity of measurement problems. This paper describes in outline these potentially dominant fibre optic sensor technologies and recaps the current State of the Art in the demonstrated performance levels. Finally some prospects for future trends are outlined.
Pressure Sensors Based On Incoherent Diffraction Effect
Jean Ebbeni, Harry Sendrowicz
The well known moire pressure sensor, where one grating is fixed and the other moves with the load, is improved by taking in account the influence of partial coherence effects. Introduction of a specified air gap between the two gratings diminishes drastically perturbations due to parasitical vibrations of mechanical creeping. Use of optical fibers allows a local pure optical measure.
On The Use Of An Optomechanical Sensing Head In Time-Of-Flight Laser Rangefinding
M. Koskinen, R. Ahola, J. Kostamovaara, et al.
The time-of-flight (TOF) laser rangefinding technique has recently found many applications for industrial measurement purposes. The electronics of a rangefinder can be separated from the sensing head using optical fibres. In spite of many advantages such as non-sensitivity to demanding environments, optical fibres also introduce some potential measurement errors. To analyze the effects on performance of using long optical fibres in pulsed TOF rangefinding, an experimental laser rangefinder intended especially for the measurement of to-and-fro motion was developed. The rangefinder has a separate optomechanical sensing head, which is connected to the electronic unit by a shielded cable containing the transmitter and receiver fibres. The transmitter has a pulse repetition rate of 1.3 MHz and the receiver includes a high speed transimpedance preamplifier and automatic gain control electronics. An analogue time-to-amplitude converter is employed to obtain high speed, high resolution measurement. The performance of the rangefinder with different fibre lengths is analysed here, concen-trating mainly on the resolution and differential non-linearity, the integral non-linearity being of less significance due to the AC nature of the measurement.
Fiber-Optic Interferometric Sensor : Simultaneous Measurement Temperature And Pressure
H. Bellil, P. Meyrueis, A. Charari
The use of a fiber-optic Mach-Zehnder interferometer to meassure temperature and pressure is described. The pressure and temperature changes are observed as a motion of an optical interference fringe pattern. Values are calculated for the pressure and temperature from the fringe motion.
Laser-Doppler Anemometry In Hydraulic Research
M. F . Proenca, A. A . Ribeiro
The paper refers to flow problems on gates already built in Crestuma-Lever power plant. Vibration problems are mentioned and the interest of the knowledge of the way the flow develops on the upper and lower parts of the gates is showed. Laser Doppler measuring technique is generally described and Laser Doppler measurements around gates are presented.
Laser-Doppler Measurements Of Impinging Jets
J. M. M. Barata, D. F. G. Durao, M. V. Heitor
Laser-Doppler measurements of the velocity characteristics of the flowfield resulting from the impingement of single and twin jets against a wall through a low-velocity crossflow are presented and discussed together with visualization of the flow. The study provides a basis to improve the understanding of the physical mechanisms acting in practically relevant flows such as the flowfield created underneath a vertical take-off aircraft, as well as reliable data to evaluate the numerical solutions of the equations of motion which use turbulence models in order to predict this type of flow.
A Cost-Effective LDV System
C. Allan Hobson, Michael J. Lalor
A low cost laser Doppler velocity measuring system has been developed, and is described in this paper. The principles of period measuring instruments are reviewed and the system parameters important to the measurement are considered. It is shown how the parameters may be adjusted to allow the development of a relatively low-cost instrument which does not have the high performance characteristics of some commercial instruments, but which is more than adequate in performance for most industrial applications.
Laser Diagnostics Of The Flow In Industrial Burners
D. F. G. Durao, M. V. Heitor, A. L. N. Moreira
Laser based visualization of the flow and laser-Doppler measurements of mean and turbulent velocity characteristics are reported in the developing region of the reacting and non-reacting swirling flows of a model of an industrial oxy-fuel burner. The burner consists in a central axysimmetric swirling jet surrounded by sixteen circular jets, simulating the injection of oxygen in practical burners. The experiments have been carried out to investigate the three-dimensional characteristics of the near burner region, the flame structure and the process of flame stabilization and show the efficiency of laser-based diagnostics to study the aerodynamics of industrial burners. The results suggest that the flame may be represented by laminar flamelet concepts and that the flow becomes axisymmetric upstream of one central-jet diameter. The stabilization of the flame occurs in the vicinity of the quarl, away of the central, swirl-driven recirculation zone. The effect of swirl is, however, essential to improve turbulent mixing and to decrease the entrainment of ambient air into the quarl.
Laser Doppler Measurement Of Fan-Belt Slippage
Finn Mengel
An optical system has been developed for measuring the slippage of a flexible fan-belt in an automobile engine. The system is based on the laser Doppler effect and measures the difference in angular velocity of two bodies, rotating at almost the same speed. Using a differential principle, the system output is independent of pulley eccentricity, belt deformations and engine vibrations.
Determination Of Pressure Changes In Fluids By Means Of Gas Bubbles
H.-St. Buchkremer, C. G. Stojanoff
The subject matter of this paper is the presentation of a new method for the determination of high frequency pressure fluctuations in a liquid. The objective is to perform this measurement without any significant disturbance of the fluid. This technique utilizes gas bubbles in a liquid and evaluates dynamically the laser light scattered by the bubbles. it should be emphasized, that this type of measurement requires the use of an insoluble gas. Hence, the size of the bubble depends on the fluid pressure and on the surface tension. Thus, changes in the fluid pressure cause bubble size variation and modulation of the scattered intensity. The corresponding frequency is thus a measure for the rate of growth of the bubble and provides direct information about the changes in the fluid pressure. The theoretical interpretation was tested in an experiment and compares well with experimental results. This technique could be of considerable importance to the study of cavitation, bubble implosion and other dynamic phenomena in fluids.
Strengths And Limitations Of The Phase Doppler Technique For Simultaneous Measurements Of Particle Velocity And Size
D. M. Livesley
Laser Doppler velocimetry (LDV) is a well-established technique for making non-intrusive measurements of particle velocities in a wide variety of situations. However, the particle velocities so measured are often much more useful if the sizes of the individual particles measured are also known. While it is possible to analyse standard LDV signals to obtain measurements of particle size simultaneously with those of particle velocity in some circumstances, this method is difficult to use on a routine basis. The recent extension of LDV usually known as the phase-Doppler technique has, however, made simultaneous size and velocity measurements much more straightforward. The principles of this method and its strengths and limitations will be discussed. In particular, although in principle the method is restricted to cases where the particles or droplets are nearly spherical, evidence will be presented to show that this restriction can be relaxed if the data is processed suitably. It will be shown that as a by-product of this, it is also possible to extract information about the degree of sphericity of the material studied. Finally, application of this technique to a number of industrially important flows will be considered, and some of the problems encountered will be described.
The Application Of Lasers To Particle Size Measurement
B. Scarlett
An understanding of the phenomenon of light scattering by small particles has existed for more than one hundred years. The application of that knowledge to particle size measuring instruments has been common for more than fifty years. Many of those early instruments were based on the scattering of white light, often simple extinction measurements. The situation today is one of widespread use of laser measuring techniques in a wide variety of industries. Currently the preponderant use is laboratory based but now is the time that an extension to on-line monitoring and control is possible and will certainly occur. Three technologies which have developed enormously in the past twenty five years have made this possible. Those three developments are the laser, the optic fibre and the computer which have combined to completely revolutionise both the capabilities and the importance of light scattering instruments in industrial applications.
Measurement Of The Velocity And Size Distribution Of Droplets And Of Their Statistical Correlation
H, Burnage
Although the methods used to measure the velocity and size of moving particles are very different and hence make use of separate apparatus, it is often possible to obtain both information simultaneously, The basic equipment requested for this technique is a standard laser doppler anemometer to which two slight modifications are brought; the photomultiplier is set so as to view the measuring volume at right angles and its's pin-hole is replaced by a slit, In these conditions, the electrical output of the photomultiplier can be best interpreted. The statistical correlation between the velocity fluctuation of the particle and that of its diameter is obtained by computing the joint probability density function of these variables from the probability density of the velocity and the conditional probability density of the peaks of the envelope, This method does not require much investment on the optics which is standard; the effort is however transfered to the electronics, data acquisition and digital processing. Although it, is at present less accurate than those base on Fraunhoffer diffraction and gives relative values since it must be calibrated, it has the advantage to yield the velocity and size-velocity correlation. Moreover the electronics can still be improved and the processing speed increased by the use of a fast compiled language,
A Phase Doppler Instrument For Optical Particle Sizing
M. Saffman
The features and principles of operation of a phase-Doppler instrument for in-situ optical measurements of size, velocity and concentration are described. Examples of typical measurement results from several different applications are presented.
Particle Size And Velocity Measurement On Flows Of Transparent Or Non Transparent Spherical Particles By Laser-Doppler-Anemometry; Problems Of Practical Application
K. Bauckhage, U. Fritsching, J. Heuermann, et al.
In many applications of fluid atomization there is a high demand for point or overall measured data of size and flux of the liquid or solidified drops. For a few years the phase-Doppler-method (LDVS) besides of the Visibility/Intensity-method has proofed out as a very useful instrument for the analysis of such spray situations. In spite of the well known velocity measurement of particles by laser-Doppler-anemometry the particle sizing by this method is more complex and asks for both a more sophisticated electronic signal processing and above all a knowledge of the optical character of the particles under observation. The paper shows the influence of the light scattering character of different spherical particles on the necessary evaluation of Phase-Doppler data. After a brief description of the Phase-Doppler-method including the basic physical principles it will be shown the Phase difference dependency of doppler bursts on different photodetector positions on one hand and on the refraction index and particle size on the other. For both transparent and non transparent particles there will be compared the results of the complex Mie light scattering calculations with simplified geometrical based calculations and experiments to find out detection angles which give unambiguous particle size informations and in addition allow an experimental arrangement as simple as possible. The results show that in many cases where particles are not totally transparent a back-scatter-arrangement of the photodetectors should be possible. Although the requirement of particle's sphericity may restrict the applicability of the phase-Doppler-laser-anemometry we should confirm that very often in multiphase flow systems the dispersed particles are drops or bubbles or if solid have a spherical shape. In the latter case we only need a sufficient smoothness of particle surface. The experimental results presented here are obtained from very different fluids ranging from water to molten metal.
Flocculation/Deflocculation Studies Of Kaolin Suspensions Using LDS
M. Margarida L. F. L. ReboIa, M. Graca B. V. Rasteiro, Fernando Pita
The influence of pH upon kaolin dilute suspensions has been investigated using laser diffraction spectrometry (LDS), the results being compared with a series of sedimentation tests. Due to its ability to separately explore most different aspects, following the resultant variation of floc size distribution, this technique appears most promising, openning new perspectives for the study of flocculation processes.
Effect Of Shape, Structure And Texture On The Accuracy Of Size Characterization Of Fineparticles By Light Scattering
B. H. Kaye, R. Trottier
Deconvolution of the complex diffraction patterns generated by laser inspection of a random array of fineparticles is a widely used method for characterizing the size distribution of the scattering fineparticles. Interpretive hypothesis used to deconvolute the diffraction pattern use simplified assumptions which usually ignore the diffracting effect of structural features of the fineparticle profiles. For quality control and processing research this is not a serious limitation of the methodology. However if one tries to use these methods to evaluate the size and concentration of respirable dust one must adjust the data processing involved in the deconvolution to take into account various structured features of the dust. In this communication the effect of sharp edges and fractal structure in respirable dust such as quartz, diesel exhausts, flyash and nuclear melt down fumes on the group diffraction pattern of a random array are discussed.
Using Fast-Fourier-Transform (FIT) For The Phase-Doppler-Dp Erence-Analysis Of Powder Metal Sprays
K. Bauckhage, A. Schone, TH . Wriedt
Application of the phase-Doppler-difference-analysis to ,spraying and compacting molten metals to measure particle size and velocity distributions is difficult because of the high background noise level of the signals detected by the photodetectors. Common counter processors will not work properly with such noisy signals. Therefore a modified laser-Doppler-processor based on the fast Fourier transform is described and its performance evaluated by simulation and by analysing signals originating from rough and nonspherical CuAl particles.
On-Line Measurement Of Crystal Size And Shape Using Combined Optical Techniques
A. Boxman, B. Scarlett
A forward laser light scattering technique is used for on-line control of a continuous crystallizer. The recorded scattering pattern is processed and translated into a crystal size distribution. Reliable data are a prerequisite for process control. Hence much attention is paid to both recording and data processing. Due to a number of specific features encountered, e.g. high particle concentration, wide size range, several modifications had to be made.
Building A Particle Size Analyzer
Carlos Couto, Fernando D. Carvalho, Manuel Romero, et al.
This contribution describes the design of a particle size analyzer based on the diffraction of the light of a small He-Ne Laser. The emerging radiation is received on a set of photodetectors and fed into a personal microcomputer.
Lasers For Industrial Materials Processing
Alberto Sona
A rewiew is provided of the state of the art and perspectives of High Power Lasers for industrial materials processing. Special attention is given to the solid state lasers (Nd-YAG) and to the gas lasers (CO2) of industrial interest. Excitation of the active medium and heat removal techniques, time and space control of the emission and beam transport problems are discussed. The expected improvements and future evolution are also out-lined.
Some Viewpoints On Laser Automation And Processing Quality Control
W. M. Steen, L. Li
Since 1970 high powered lasers have been used in industry for cutting, welding and surface treatment. These operations are normally automated by some form of pre-programmed operation. None of the existing industrial systems incorporates process quality feedback control. The operating routines are all prefixed regardless of possible undesired changes requiring resetting of those conditions during operation. As a result the quality of products can not be guaranteed except by past experience. This problem has become increasingly apparent to industry and research scientists, particularly now that it may be soluble. Many attempts have been made to find a solution; so far they have served to show that the task is complex. This paper reviews previous achievements in laser automation and process feedback control. It discusses some of the techniques which might be employed for future developments.
Robot Guided Laser For Three-Dimensional
R .-D . Schraft, G. Hardock, M. Konig
The laser is a non-contacting, forceless tool which is nearly free from wear. In regard to its tasks and its potential for process automation due to ease of control of the laserparameters, laser processing seems to be predestinated for flexible manufacturing. By the use of free moveable, robot guided laser beam guiding systems, the laser as a tool, offers a new potential for widely varied tasks. In an overview on existing concepts for laser beam guiding systems, the possibilities for laser beam handling are discussed and system concepts of coupling laser beam guiding systems to a robot are presented. With the help of a pilot laserworkstation with a robot guided, free moveable laser beam guiding system, realised at the Fraunhofer-Institute for Manufacturing Engineering and Automation (IPA), the different components of a flexible laserworkstation are specified. Basing on this the principal explanations of robot guided laser beam guiding systems are introduced. Different kinematic diagrams show the influence of the combination of laser beam guiding system and robot kinematic due to the workenvelope of the entire system. Investigations concerning the static and dynamic behavior of the system will show the requirements for a design of a reliable laser beam guiding system. A consideration of the economy of different laserworkstations delivers economic indexes which show the cost ratio between the different variants.
Seam Following For Automated Welding
J. Lucas, J. S. Smith
The use of laser light and vision systems for the identification of seams to be welded is discussed. Systems are described which are compact and allow access to remote locations by using coherent fibre optic bundles. Present computing speeds allow simple structures to be identified within the time (~20ms) required to capture a frame. Future developments are discussed and are limited to the enhancement of the computing power especially by use of the transputer. This will allow very complex structures to be analysed as well as real time adaptive control to be introduced for the faster welding processes. The role of expert systems will become important to check and maintain weld quality.
Development Of A Stabilized CO2 Laser
Nuno Silvestre, Jose S. Lemos, M. Ribau Teixeira
A cw CO2 laser capable of tuning through a number of rotational lines using the laser signature technique has been developed. The optogalvanic effect is used in a control loop for active stabilization. Frequency fluctuation in the long term is better than 3 parts in 107 . The laser has an output power of 6 W on the 10P(20) line.
Beam Delivery System For A CO2 Laser
D. Appelt, A. Cunha
In order to integrate a low power (70 W) CO2 laser into a materials processing system, a device has been developed which enables the beam emerging the laser to be guided down to the workpiece, on which it is focused. The resulting system includes a mirror which is located in such a way as to deflect the beam by 90°; a means is provided for its fine adjusting in two mutually perpendicular directions. The vertical tube was designed in order to allow the alternative fitting of lenses with the most usual focal lengths in the intended range of applications. The terminal nozzle was shaped taking into account the need for either a cutting gas shroud or a means for drawing away the smoke developed during cutting.
Laser Cutting
Flemming O. Olsen
In this paper the laser cutting technology is shortly described. The history of the modern laser cutting technology is reviewed. The laser cutting process and its most important parameters are described briefly. Finally the trends in the technology is discussed briefly.
Thermical Modelisation Of Laser Cutting Process
S. F. Yuan, M. Querry, C. Bedrin
This paper presents a method of thermical modelisation of laser cutting in the monodimensional case, using the finit differences method : this model has the simplicity convenience and can resolve the problem of the cutting front mobility.
Heat Conduction And Mass Transfer In Laser Cutting
D. Schuocker
The most important phenomena contributing to laser cutting are heatiu of the workpiece by absorbed laser radiation and exothermic reaction, heat loss due to t rmal conduction and evaporation and melting of the workpiece in the vicinity of the focus of the laser beam. Material removal takes place since liquid material is blown away by the oxygen flow and due to evaporation. To obtain a deeper insight into these main phenomena of laser cutting and to understand their relative importance, heating of the workpiece and material removal will ne closely regarded and analyzed.
Report On Current CO2 Laser Applications In Japan
M. Kanaoka, M. Kitani
Since high-precision cutting has been achieved by laser, this has widened the field of applications of laser cutting, largely contributing to making the laser technology popular. This report describes the pulse characteristics and beam quality which have contributed to achieving the high precision cutting, by showing the relationship between them and cutting accuracy. The laser cutting applications in Japan are also introduced.
CO2 Laker Cutting Of Titanium Alloys
J. Powell, M. Jezioro, I. A. Menzies, et al.
An in-depth experimental investigation has been carried out into the cutting characteristics of titanium alloys which has led to the development of new techniques. Problems usually associated with CO2 laser cutting of Ti alloys (i.e. dross and 02, N2, contamination) have been eliminated by the use of auxiliary argon jets employed during cutting. Cuts generated by this multiple inert gas jet technique have been analysed using profilometry and surface chemical analysis. Oxygen and nitrogen contamination levels were found to be lower than for mechanically guillotined edges. Surface roughness values were of the same order of magnitude as milled samples.
Cutting And Engraving Of Materials With A CO2 Laser
D. Appelt, A. Cunha
Owing to its special characteristics, radiation of a CO2 laser may be used as an efficient tool for processing materials. The present paper describes some possible applications which have been developed with a low power (50 W) laser for cutting and/or engraving various non-metallic materials - acrylics, cardboard, veneer, natural and synthetic leather, glass, ceramics, etc. - as well as marking of anodized aluminium. In each case operational conditions leading to best results were found experimentally, acting on parameters like laser power, processing speed, assist gas or suction.
Marble Cutting By Laser
Margarida Pires, Antonio Ferreira, Manuel Ribeiro, et al.
Through the present work on marble laser cutting, some advantages of this method over the conventional process were ascertained. Several parameters relevant to marble laser cutting have been measured, namely the cutting speed as a function of the thickness of the marble plate and the output power of CO2 Laser.
Trends In Heavy Section Laser Cutting
Ing. G. Sepold
The thermal cutting with laser allows three possible cuttings, which mainly differ in the removal of the material. If the material is mainly vaporized, then this procedure is called laser sublimation cutting according DIN 2310 (German Engineering Standardization); if however the material is melted and the melted mass is removed by a gas jet, then this process is called laser melt cutting. If an exothermic chemical transformation of the material takes place , e.g. oxydation, then the process is called oxy-laser cutting.
Photolithographic Masks For Integrated Optic Circuits Fabricated With An Ar+ Laser System
P. Boffi, O. De Pascale, C. Esposito, et al.
A computer-controlled Argon laser system for writing photolithographic masks over an area as large as 50 mm x 50 mm has been developed. Different waveguide patterns have been written and some field assisted ion-exchange channel waveguides have been fabricated directly into integrated circuit mask plates.
Laser Direct Writing Of Gratings For Integrated Optics
G. Assanto, C. Cali, S. Riva-Sanseverino
A novel technique for fabrication of thin-film gratings is reported. A CdS film, deposited onto an ion-exchanged glass waveguide, is photo-etched by a focussed Ar-laser beam. Computer-controlled movement of the sample allows for the formation of periodic structures, tested for input and output coupling. Some interesting effects due to the simultaneous presence of longitudinal and transverse gratings are discussed. We also propose the technique in the realization of integrated optical devices for communications.
Stainless Steel Cladding Of Structural Steels By CO2 Laser Welding Techniques
A. Ludovico, G. Daurelio, O. Arcamone
Steel cladding processes are usually performed in different ways: hot roll cladding, strip cladding, weld cladding, explosion forming. For the first time, a medium power (2 KW c.w.) CO2 laser was used to clad structural steels (Fe 37C), 3 and 5 mm thick, with austenitic stainless steels (AISI 304 and AISI 316), 0.5 and 1.5 mm thick. The cladding technique we have developed uses the laser penetration welding process.
Metal-Silicon Reactions With Laser Pulses
A. Luches, E. D'Anna, G. Leggieri, et al.
The work done on the synthesis of metal silicides by using different pulsed lasers (ruby, Nd:glass, excimer) is presented and discussed. We found that excimer lasers offer much better characteristics for annealing of metal/silicon systems in comparison to solid state lasers.
Microstructure And Oxidation Properties Of Laser Clad Ni70AL20Cr7Hf3 Alloys With Extended Solid Solution Of Hf
J. Mazumder, S. Sircar, C. Ribaudo, et al.
Alloys coatings for superalloys for improved higher temperature (1200°C) service life under aggressive atmospheres are of great interest at present. There is a general consensus that addition of rare earths such as hafnium (Hf) to these alloys has a pronounced effect on the oxidation resistance properties at high temperatures. In situ laser cladding technique was used to produce Ni-Al-Cr-Hf alloys with extended solid solution of Hf in a near stoichiometric Ni3Al matrix. A 10 kW CW CO2 laser was used in conjunction with a screw-feed powder dispenser to perform the in situ cladding process.
Laser Surface Engineering Of Tool Materials
A. Bloyce, T. Bell, I. M. Hancock
The very nature of laser surface melting allows for localised modification of a surface, and it is this feature which makes it ideally suited to treatment of single point cutting tools. High speed steel M42 material has been laser surface melted and in trials, the resulting microstructural modifications have produced improved cutting performances over conventionally heat-treated material. In addition, laser alloying of a low-alloy steel substrate to achieve an M42-type cutting tip has also demonstrated acceptable cutting performances. With the different wear conditions encountered in die materials, it is thought that the addition of ceramic material to the die may enhance performance, and preliminary work on surface melting and alloying of this type of substrate is also reported.
Aluminium Reflectance Under Excimer Laser Irradiation
A. Anedda, A. Mura, F. Raga, et al.
The reflectance of cold rolled Aluminium during Xe-Cl excimer laser pulse irradiation with power densities in the range 10 MW/cm2 to 14 GW/cm2 has been investigated. Plasma formation at 500 MW/cm2 without previous melting at lower power is observed. "Laser cleaning" of the surface lowers plasma threshold to the pure Aluminium value and melting of the metal is detected as well between 60 and 110 MW/cm2.
New Corrosion Resistant Ceramic Coatings By Laser Processing
S. R. J. Saunders, A. A. Ansari, M. J. Bennett, et al.
Fabrication of thick oxide ceramic coatings upon a metal substrate by laser processing has been investigated. Crucial parameters studied included beam power, diameter, overlap and traverse speed, feed powder size and coating environment. Coatings were characterised by a range of surface analytical techniques. The corrosion protection afforded by a coating was assessed in both oxidising and sulphidising environments.
Laser Surface Treatment Of AISI 420 Tool Steel
R. Vilar, R. M. Miranda, A. S. Oliveira
Samples of a martensitic stainless steel containing 0.47%C and 12.8%Cr were surface melted using continuous wave CO2 laser radiation and a multiple pass technique. The structure of the laser modified layer was studied by optical microscopy, scanning electron microscopy and X ray diffraction. The melted zone presents a narrow region near the fusion line with a ferritic--martensitic structure, that seems to have solidified by an almost partitionless mechanism. It is followed by a cellular-dendritic structure in the center of the melted trail, that consists on δ -ferrite, martensite and M23C6 carbide. The absence of austenite is surprising; it can be explained by the tempering effects of the solidification structure, due to subsequent laser passes.
Laser Welding Of Thin Sheet Of AISI 301 Stainless Steel
R. Vilar, R. M. Miranda
Preliminary results of an investigation on laser welding of AISI 301 stainless steel thin sheet are presented. Welds were made with a CO2 continuous wave laser, varying power density and welding speed. The welds were studied by optical and electron scanning microscopy, X-ray diffraction and hardness tests. Experimental results show that under appropriate conditions, sound welds are obtained, with a negligeable heat affected zoneanda fine microstructure in the fusion zone. The fusion zone shows a cellular - dendritic microstructure, with austenite and ferrite as the major constituents. Ferrite, whose content is 5 to 7%, is predominantly intradendritic with both vermicular and acicular morphologies. However some interdendritic ferrite may also be present. The characteristics of the structure suggest that the solidification mode of AISI 301 stainless steel is essentially ferritic.
Characterization Of Real Laser Beam Profiles With Few Parameters For Metallurgical Applications
Jacques Merlin, Jean Dietz, Carlos Oliveira
In first approximation the material induced effects after laser beam interaction are function of the whole transmitted energy and of the local "irradiance" (in W.cm-2) levels and gradients. Consequently 3 informations may be able to describe this beam : carried power, shape and dimensions in the interaction zone. Thus shape and dimensions of a real beam would be simply and universaly described. If we are interested by the induced effects in the straight of the beam axis, 3 parameters are sufficient to describe the beam : the incident power P, an equivalent radius r+, and an axial "spread" factor of energy distribution g(E). These parameters have been mathematically defined but they are also experimentally measurable (in particular from transmitted power through a small aperture or a slit localised in the vicinity of the work zone). The experimental characterization of a 4 kW c.w. CO2 laser (CILAS CI 4000) has been carried out for several powers (between 200 W and 3 kW). When the power increases it has been find that r+ increases and g(E) stays nearly constant in spite of mode evolution. Presently the real-time evaluation of these parameters is investigating. Moreover these 3 parameters can be directly introduced in simplified analytical tridimensional thermal model, and so the behaviour expectation and the working parameters fluctuations effects (for example "mode" changes) become easier. At last this approach may be able to carry out "objective" comparison between the various high power lasers in different laboratories.
Energy Distribution Analysis Of High Power Laser Beam From Spots On Paper
J. Merlin, C. Oliveira, J. Dietz
When a laser beam radiates an isolant material like paper during a small period of time (<0,is), toe induce,, degradation can be considered proportional to the incident energy density ("fluence"). This pnenomenon can be used to vizualise the laser beam profile before or after crossing an optic device. The beam mode , its possible fluctuations, and toe interference phenchluna introduced by optic elements can be easily evidenciated (it is only necessary that fluence be inciudee hetween 1 and 20 J/cm2). In a quantitative view-point the observed degradations (level of coloration, burn) can be standardized in fluence. So for a given interaction time it is possible to define the local density power ("irradiance" in W/cm2), necessary to induce the observed degradation. Consequently it is possible to reconstitute the energy repartition profile of the beam; this was achieved for the case of c.w. CO2 laser Oi 4 kW for different powers. This procedure requires a good quality paper (type "printer inkjet paper") and the accuracy can be ameliorated utilizing a "printer thermal paper". An image aoijuis software allowing toe deduction of the intrinsic characteristics of the beau is being studied.
Measurement And Prediction Of Surface Temperature In Relation To Laser Surface Hardening Of Metals
B. S. Yilbas, R. Davies, Z. Vilbas, et al.
When the surface of the material is heated above the critical temperature with a laser beam, metallurgical changes occur in the surface region of the material. As the laser beam passes, quenching of the heated surface by the underlying mass of cold metal can produce a transformation hardening depending on the cooling rate. Therefore, the prediction and the measurement of cooling rate in surface hardening is essential. To determine the cooling rate experimentally, the surface temperatures of laser heated workpieces were measured using fast response thermocouples while the surface temperature distribution was predicted theoretically for four different workpiece materials.
New Type Of Modulator For Intense CO2 Laser Radiation And Its Applications
Gisbert Staupendahl
This paper reports on a new type of modulator which can be used for many applications of intense CO2 laser radiation. The modulator is based on the principle of the Fabry-Perot interferometer and acts as a beam splitter with variable reflectivity which is placed outside the laser cavity. By means of the tuning of the spacing between the two plane parallel interferometer plates the intensity of the transmitted as well as the reflected part of the incident laser beam can be modulated. The principle of construction, typical properties and some characteristic applications are given.
Laser-Induced Formation Of SiO2-Layers For Microelectronics
H. Sigmund
After a short overview about the different techniques of the Si02-formation by photo-induced methods used in microelectronics, the laser-induced deposition of Si02-layers on silicon wafers from TEOS by ArF excimer laser are depicted in more detail and the deposition conditions are outlined in dependence of substrate temperature, partial pressure and laser fluences. The physical properties of the Si02-layers were investigated by FT-IR spectroscopy and ellipsometry; the electrical properties of CV-characteristic, mobile ion density, interface state density and breakdown voltage are given.
Progress In Laser Chemical Vapor Deposition Of Silicon Thin-Films
Vitor Baranauskas
Laser Chemical Vapor Deposition (LCVD) has been attracting a considerable amount of interest to deposit thin-films for microelectronics structures. In this paper we will discuss the progress obtained from a series of experiments of several laser-based methods, taking in to particular consideration only the Silicon deposition. Depending on the gas and kind of laser used different kinetics can be selectively induced leading to distinct film-morphologies and diverse growth parameters. LCVD processes also offers the capabilities of reduced temperature processing and mask-less patterning for sub-micron resolution. Further investigations are needed to explore the wide potential of LCVD applications.
Laser Interferometer For Optical Testing Using Nonlinear Optical Effect
C. P. Grover
The interaction of light from a relatively medium power CW laser with a nonlinear medium, such as nematic liquid crystals, has been used to devise an interferometer for measuring aberrations of the incident beam. The reorientation of anisotropic molecules of the medium contributes to the induced refractive index change An that is usually a strong nonlinear function of |E|2. The associated self-focussing and diffraction effects produce a spherical beam which is used as the reference wave. The operation of this common-path interferometer can be described by taking analogy with a point-diffraction interferometer.
Modern Optical Coating Technologies For Low-Loss Dielectric Films
H. K . Pulker
Highest quality dielectric films are required today for various optical applications. Many inorganic compounds which were difficult to deposit by conventional tech-niques in form of well adherent, dense, hard, and stable low-loss films are now routinly synthesized by reactive gas discharge plasma and energetic ion and/or coating material atom processes. A survey over such PVD coating technologies and the resulting film properties is given in this paper.
Design Of MESFET Optical Amplifier
Mario N. Armenise, Anna G. Perri
GaAs MESFETs, originally designed for microwave applications, have become an important com ponent of receivers in high-speed optical telecommunication systems. For these applications, the crucial point in the device modeling is the evaluation of the induced gate noise and its correlation to the channel noise. In this paper the design of a low-noise small signal optical amplifier using GaAs MESFET is carried out. The principal noise sources of GaAs MESFETs are analyzed in order to completely characterize the equivalent model. Particularly channel-noise represents the dominant effect in the determination of the optical receiver sensitivity. Total input noise current of the optical amplifier, due to correlated gate and drain MESFET noise, has been estimated in order to evaluate the excess channel-noise factor r for different values of photodiode capacitance. This procedure allowed to choose the photodiode with minimum noise. At last, scattering parameters, minimum noise gain, gain-frequency dependence and bandwidth of the amplifier have been evaluated in the frequency range of interest.
Ion Beam Processing Of Multilayer Semiconductor Structures
J. M. Zavada, R. G. Wilson, J. Comas
The redistribution of implanted ions within GaAs/AlAs multilayer structures due to post-implantation furnace annealing is reported in this paper. The structures were grown by molecular beam epitaxy on GaAs substrates and implanted with either hydrogen or beryllium ions. After furnace annealing at temperatures up to 700 C, these samples were examined using secondary ion mass spectrometry. The measurements show that the hydrogen and the beryllium atoms redistribute with post-implantation annealing and that both species accumulate at the buffer layer/substrate interface. The concentration of atoms at this interface can exceed 1E19/cm-3 and may be related to the crystal imperfections arising during the inital stages of epitaxy. The significant redistribution of implanted ions may also alter the optoelectronics properties of multilayer semiconductor structures processed in this manner for laser applications.
Calculation Of The Ambipolar Diffusion Coefficient Through Lasing Action In Gases.
P. Persephonis, B. Giannetas, R. Rigopoulos
A new method to find the ion density of a gas at any time after the discharge is described. In this method the overvoltage of a fast discharge in a gas or its lasing action can be used. That is to say, knowing the experimental values of the actual starting voltage of a pulsed gas discharge or the laser output and comparing them with the relevant theoretical values, the ion density can be found. The result of this procedure is the calculation of the ion density at a time after the discharge equal to the inverse of the high voltage pulse repetition rate. Thus, by changing this pulse repetition rate the temporal behaviour of the ion density is found. An application to the N2 gas leads to the calculation of the ambipolar diffusion coefficient, the value of which is in sufficient agreement with the one in the literature.
Off-Axis Elliptical Zone Plate For Nonsymmetric Fourier Transforming
S. Bara, C. Gomez-Reino
An off-axis elliptical zone plate (EZP) together with refractive optics has been used for obtaining the 2-D nonsymmetric Fourier transform (NFT) of a given object with parallel beam illumination. The NFT thus obtained is exact, excepting a linear phase factor due to the carrier spatial frequency used in the EZP recording. Experimental results show the ability of this system for separating quasi-unidimensional spectra of slightly different orientation.
Rapid Determination Of The Wobbe Index Of Natural Gas
Onno Florisson
A fast response Wobbe meter for natural gas is described. The working principle of the Wobbe meter is based on a relationship between the Wobbe index, the concentration carbon dioxide and nitrogen and the specific density of natural gas. The concentrations are determined by Raman spectroscopy. A HeNe laser serves as the light source which generates Raman scatter in a cuvette filled with natural gas. A part of the scattered light is picked up and passed by two fibre optic cables to detection equipment. Filters are used to the allow N2 Raman light respectively CO2 Raman light to pass. The power of the light passing the filters is determined by photomultipliers. The concentrations are calculated from the power of the Ramen light signals, the pressure and temperature of the gas flowing through the cuvette, the laser power and callibration data. The accuracy of the concentration meters is better than 0.25% (gas 100%). This figure can be attributed to the statistical fluctuations of the intensity of the Raman light and to the way of estimating the background of the light signals. The response time is only 8 seconds. The accuracy of the Wobbe meter is better than 0.25 MJ/m3 which is good enough for a control instrument.
In-Situ Measurement Of Ammonia With A 13CO2-Waveguidelaser System
H. Neckel, J. Wolfrum
A laser gas monitoring system has been developed to measure in-situ concentrations of gaseous pollutints (in our case ammonia) at various temperatures. The heart of the system is a tunable 13CO2-waveguide laser. By varying the resonator length the laser is frequency modulated between two neighboring emission lines. One line is absorbed by the species investigated, while the other is used as a reference. By this referencing the system is autocalibrated continously. The high spectral resolution of the laser method supresses interference by other species. Fast evaluation of the digitalized signal shortens the measurement time to less than one minute. The lasers high output power is used in a multiple path arrangement, which allows the detection of ammonia concentrations in the one vppm range. First results of measurements in a power plant are reported.
Laser Excited Synthesis Of Sub-Micron Powders
J. G. M. Becht, B. A. Bauer, P. J. van der Put, et al.
The laser activated synthesis of silicon and silicon nitride powders has been studied using gaseous reactants. The use of non-IR-absorbing, chlorinated silanes requires the application of a sensitizer, which transfers the thermal energy to the reactants. The influence of the sensitizer sulphur hexafluoride on the laser activated reactions of dichloro silane and silicon tetrachloride in the presence of ammonia has been studied.
Optical Implementation Of The Hopfield Model Using A Spatial Light Modulator Discussion Of Properties And Performance
Marc Torzynski
In this paper we propose an optical design for implementation of neuronic Hopfield network. We describe the algorithm and its potential possibilities as associative (or content addressable) memory. We then describe the optical set (using a magneto-optic spatial light modulator) and explaning its operating mode: the binary transparency of the SLM does not allow a direct and accurate experimental realisation of the theoretical algorithm. However, there is a particular setup that can implemented it powerfully but with a reduction of the effective number of neurons. The operating speed is then evaluated from the characteristics of the SLM "Sight-Mod" manufactured by SEMETEX corp.: the maximun operating frequency seems limited by the speed of the optical valve.
Insulating Materials For Optoelectronics
F. Agullo-Lopez
Optoelectronics is an interdisciplinary field resulting from the interaction of Materials Science, Electronics Engineering, Information Theory and Fundamental and Applied Optics. Basic functions of an optoelectronic system include the generator of the optical signal, its transmission and handling and, finally, its detection, storage and display. A large variety of semiconductor and insulating materials are used or are being considered to perform those functions. In this conference, we will focus on the tole of insulating materials, mostly oxides. For signal generation, tunable solid state lasers, either vibronic or those based on colour centres will be briefly described, and their main operating parameters summarized. A reference will be made to some developments on fiber and waveguide lasers.
A Laser Induced Fluorescence Immunoassay System For The Detection Of Salmonella And E. Coli
R. W. Wygant, S. P. Almeida, M. D. Pierson, et al.
Total internal reflection fluorescent immunoassay techniques provide a powerful method of detecting biological antigens. A laser system has been developed to record the evanescent wave excited fluorescence emitted from the dye labeled polyclonal antibodies developed for Salmonella spp. and E. Coli 0157:H7. A cw argon laser tuned at 488 nm was used to induce the emitted fluorescence at about 520 nm. Measurement of the fluorescence was performed via an optical multichannel analyzer, on-line to a microcomputer. Antigen samples of varying concentrations were analyzed to test the operation of the system. A description of the laser detector is presented in this paper.
Holographic Investigation Of Different Types Of Surgical Fixing Devices
Halina Podbielska, Henryk Kasprzak, Gert von Bally
The method of double-exposure holographic interferometry was applied to study the behavior of lower leg bones supported with different fixing devices. The torsion and bending was examined for both types of fixators: an external one (Orthofix type 10000) and an internal one (osteosynthesis AO plate, Howmedica). The influence of the fixation on the mechanical response to the external load of the supported tibial shaft is discussed. The advantages of holographic interferometry in the above investigation are pointed out.
Holographic Endoscopy
G. von Bally
The introduction of holographic metrology into endoscopy is the decisive step towards a metrological basis for a quantitative diagnostic within body cavities, with the advantages of holographic interferometry such as large focal depth imaging, non-destructive, non-contactive, and high-resolving analysis of structure, form, deformation and vibration of the object under study. There are two possibilities of holographic endoscopic recording: at the distal end within the instrument or with an external holographic camera. In both cases optical fibers can be used for easy handling and flexibility.
New Devices For Controlling The Interaction Of High-Power Laser Light With Anorganic And Organic Materials
Pal Greguss
Two unconventional methods, which may be used in some cases to control heat conduction conditions responsible for secondary effects both in laser surgery and in laser material transformation, are presented. The tools developed for this purpose are based either on thermoelectrically controlled (TEC) or on thermodynamically controlled (TDC) temperature pattern generation around the acting laser beam. Using TEC laser scalpel secondary tissue damages may be avoided, while transformation hardening by laser radiation may be controlled through the thermodynamic effect known as Ranque-effect.
Laser Speckle Size And Temporal Transfer Function In Human Vision
J. Perez-Carpinell, V. Climent
Using a blue laser stimulus we measured TMTF with speckle sizes of 19.1 µm, 3.3 µm and absence of speckle. Our results indicate, if we compare the TMTF curves obtained for different speckle sizes, a gain of modulation due fundamentally to the presence of the spec kle; in the low frequency region this gain of modulation can be explained in terms of inhibitory effects. On the other hand, we observe by using the diffusion-inhibition model, that the presence of speckle in the test-field produces a delay of 12 ms and a reduction of the height of the response, with respect to that obtained in the uniform test (with absence of speckle).
Lasers In Medicine
L. M. Bernardo
Fifty people around have participated in the workshop "Lasers in Medicine": most of them participants on the previous days on the conference "Laser Technologies in Industry", also some invited physicians and others interested in the topic from various University Departments.
Lasers In Ocean Science
S. P. Almeida
A workshop meeting on Lasers in Ocean Sciences was held on June 9, 1988 the day after the conference on Laser Technologies in Industry in Porto, Portugal, June 6-8, 1988.