Conventional optical spectroscopy of solids, semisolids, smears, and gels generally suffers from excessive light-scattering and opacity effects. Recently a new spectroscopic technique, called photoacoustic spectroscopy has been developed which overcomes both of the above problems. This new technique and some of its current applications are briefly described in this paper.
We have developed a jet stream dye laser which operates with an argon or krypton laser pump. With a 3000 grooves per mm holographic grating, we can demonstrate that the system is a longitudinal single mode without any additive, optical component. The high quality of the exit beam, coupled with its remarkable efficiency, allows this laser to be used in frequency doubling experiments and in pumping of other dy lasers (for example, cresyl violet). Some potential applications in spectroscopy, in particular in the field of Raman Spectroscopy and Atomic Absorption are discussed.
Laser-based spectrophotometric methods which have been proposed for the detection of trace concentrations of gaseous contaminants include Raman (LIDAR) and passive radiometry (LOPAIR). In this report, we discuss a simple long-path laser absorption method (LOLA) which is capable of resolving complex mixtures of closely related trace contaminants at ppm levels. A number of species were selected which are most likely to accumulate in closed environments, such as submarines or long-duration manned space flights. Absorption coefficients at CO2 laser wavelengths were measured, accurate to ± 3% or better, for each of these species. This data was then used to determine the presence and concentration of the contaminants in prepared mixtures of twelve to fifteen gases. Computer programs have been developed which will permit a real-time analysis of the monitored atmosphere. Minimum detectable concentrations for individual species are generally in the ppm range, and are not seriously degraded by interferences even in complex mixtures. Estimates of the dynamic range of this monitoring technique for various system configurations, and comparison with other methods of analysis, will be discussed.
A 1975 consensus by electro-optic fiber communications technologists emphasized forty-four (44) applications as being important uses of this rapidly expanding area. Upon analysis, eight major areas appear to be the most cost effective for the next seven years. This paper discusses the nature of such systems and markets and their value-in-use. The 1975 applications cited are: 1. Telephone loops 24. Nuclear plants including fusion develop-2. Telephone trunks ment 3. Telephone terminals and exchange uses 25. Oil and chemical (stationary and mobile) 4. Internal computer links 26. Electronic and electrical instrument 5. Inter-computer links systems 6. Hard-wired computer terminals 27. Space program 7. Long-haul data transmission 28. Medical 8. CATV trunks 29. Supervisory control (low data rate) 9. CATV distribution 30. Sonobuoys 10. CCTV 31. Electric power control (line type) 11. High capacity lines (vs. microwave 32. Substation control cable) 33. Computer-video electric power systems 12. Private broadband networks 34. Hazardous areas 13. Municipal services 35. Long-line isolators 14. Military aircraft 36. Microwave-optical interconnections 15. Civilian aircraft (entrance links) 16. Military ships 37. Laser power guides 17. Naval-towed arrays 38. Signal switching (proximity coupling) 18. Special tethers 39. Satellite ground stations 19. Submarine cable 40. Facsimile systems 20. Civilian ships and tankers 41. Memory delay lines 21. Army cable, connectors, and systems 42. Lightning-resistant instrumentation 22. Secure communications 43. Hospital patient monitoring 23. Cable congestion relief 44. Telemetering Considering value-in-use and cost effectiveness, however, in the near term the fiber optic applications markets of economic significance are: 1. Telephone and non-telephone common 4. Industrial automation (discrete factory carriers automation) 2. Cable television 5. Other industrial automation applications 3. Satellite ground station links and 6. Process controls local loops 7. Computer applications 8. Military applications
In March 1976, the Ministry of International Trade and Industry of Japan initiated a development project of an optical fiber trans-mission system with a budgetary allocation of approximately $17 million over the four-year period 1976-79 through the Visual Information System Development Association (VISDA). This project is one of the most advanced projects in the field of optical fiber communication systems applied to interactive CATV. VISDA emphasizes that an optical fiber communication system has advantages over a coaxial cable system:
(1) Large transmission capacity per cross-sectional area.(2) Low price projection per information channel.(3) Stimulation of the related optical fiber system industry. The main objective of this project is to explore an ideal information transmission system for a modern society where there exists a high density of information storage and transfer. Toward this end, the Japanese Government and related industries are determined to combine their efforts for the successful completion of this ambitious project of an optical fiber information transmission system.
The design and performance of high radiance, linear, Burrus type GaAs-GaAlAs double heterojunction LED's is described. Characteristics such as radiance, response time, spectral width, efficiency and reliability are considered. The properties of these surface emitting structures are contrasted with those reported for high radiance LED's having an edge emitting geometry. The coupling characteristics and total power available from both device designs when coupled to optical fibers typical of those employed in practical systems are described. Results are presented of measurements made of LED linearity as functions of structure, drive level and doping. Implications of these linearity measurements on the use of LED's for analog signalling are discussed. Circuit compensation techniques which have been employed to reduce the non-linearities in optical transmitters are briefly reviewed.
The implementation of an analog video optical fibre link is a more difficult problem than a digital system. The signal-to-noise ratio (SNR) requirement is more stringent (40 to 60 dB as against typically 20 dB for a digital system), and account must be taken of other significant requirements such as differential gain distortion, amplitude flatness, and group delay. Close attention must be paid to equalizer design and modulation linearity. The performance that can be achieved with analog TV optical fibre links is examined in the light of current and anticipated near-term capabilities of optical sources, fibres and detectors, including light emitting diodes and semiconductor lasers, and step-and graded-index fibres. Both baseband and subcarrier FM modulation are analyzed, and the corresponding attenuation, dispersion, and distortion limits discussed. The analysis is extended to multihop links, and consideration given to choosing an optimum (rather than a maximum achievable) amplifier spacing.
Theoretically and experimentally, we investigated two methods for the excitation of single modes in plane symmetrical multimode waveguides. I. The first method performs coupling through the polished front face of the guide. For this an astigmatic system generates a focal line a short distance in front of the front face and parallel to it. Part of the divergent light proceeding from the focal line couples into the guide. Mode selection is achieved by simple translation of the guide. Typical values of the coupling efficiency are about 10%. A disadvantage of this method is that modes cannot be excited purely. II. In the second method coupling into the symmetrical waveguide is achieved by shining light through a cladding onto a sinusoidal metallic grating at the opposite film-cladding interface. Coupling in the first order of reflection is accomplished by the grating. Mode selection is done by rotating the system. The dependence of the coupling efficiency on the grating height was investigated. Maximum efficiency is about 30% with very good mode-purity. This method is more advantageous compared to the first. Aside from high efficiency and mode-purity it is particularly the good handling and the protection of the coupler inside the system, which makes this method recommendable.
The basic problems of quantitative determination of mechanical strain through holographic interferometry are discussed. A solution based on the calculation of local derivatives ofthe holographically recorded surface displacements is described. This method uses essentially heterodyne holographic interferometry for the quantitative determination of the surface displacement from the fringe pattern in the image plane. With this techqque the interference phase can be measured with an accuracy and reproducibility of ± 0.33at any point in the fringe pattern, corresponding to an interpolation of better than 10-3 of one fringe-Numerical examples are given for the sensitivity and accuracy of surface strain measurements and the determination of bending and torsion. Experimental results for bending and torsion of arbitrarily curved and twisted space beams, such as turbine blades, are reported. Accuracy and agreement with theory are within a few percent.
Speckling, a familiar phenomenon resulting from the high coherence of laser beams, is very often a nuisance in image formation with coherent light as well as in holography, but has practical applications sometimes superior to those of holography.
A new acousto-optic tunable filter utilizing collinear acousto-optic interaction along the direction near to the optic axis is proposed and demonstrated by using LiNbO3 crystal. Using this near axis interaction lowers the driving acoustic frequency and also expands the angular aperture in the ordinary plane. The acousto-optic figure of merit M2(=n03ne3p2/pv3) of this filter is 7.5 x10-18 sec3/g, and tuning from 7000Å to 4200Å can be obtained by changing the acoustic frequency from 56MHz to 119MHz. At 5145Å, the filter bandwidth of 11 Å and the angular aperture of about 6° in the ordinary plane have been obtained.
The electro-optical birefringence technique has required generation of very high voltage pulses (4kV) strictly adjustable in duration with 4 ns field cut-off duration. The multiple reflection cell designed increases the birefringence of the polarized laser beam. An optimal number of reflections is found by theory and experiment. A computer provides a pure signal curve from a signal initially embedded in electrical noise. The statistical method employed consist of making the signal variance (and the time variance) a minimum. We have found a correlation coefficient equals to 0.99. So, the reliability of the relaxation curve is strongly stressed.
Advantages of using optical wavelengths for informationstorage and processing has been widely discussed in the last few years and extensive research work has been done on optical memory sys terns and storage medium because powerful coherent sources are now available and allow theoritically a diffraction limited storage density. Several laboratories have already demonstrated potential capabilities of optical systems coinpared to magnetic technology but it now appears clearly that, optical memories sys tern will only find a place in the hierarchy of storage systems used to day if they will courpete in capacity, acess speed, and very inportant in cost per bit of stored information. Considering these requirements, the "Optical Videodisc" is a pood example of a cheap read only optical storage sys tern providing 10 bits capacity, nearly diffraction limited-storage density and video recording and readout bandwidth. Two main principles of optical storage techniques have been considered up to now : bit oriented memories provinding sequential acces to the storage medium ; page organized holographic memories provinding parallel writing and readout and microsecond random access speed by laser beam deflection. Each of these principles were applied to permanent storage media such as photographic plates or photopolymers materials but many attemps are actually made in the field of read-write optical memories which need erasable photosensitive materials ; Thermomagnetic ; Thermoplastic ; Photoretractive materials are the most attractive candidates for read-write systems which are actually mainly limited by the storage material performances
The first thermomagnetic hologram formation has been published by R.S. Mezrich /1/. The hologram is formed by the interference of two coherent light waves at thin recording medium, if regions of ferromagnetic recording material, corresponding to regions of high light intensity are heated above the Curie temperature. In these regions the direction of the magnetization is switched by bias magnetic field and/or demagnetization field of the ferromagnetic film. The process of magnetic hologram formation is an indirect one in that the temperature variation caused by the absorbed light intensity pattern leads to the final magnetization pattern. It is therefore of critical importance to determine the temperature profile in magnetic medium, caused by the incident light intensity pattern.
Phototheriloplastic devices represent a candidate for optical holographic storage and real-time optical information processing. The typical band pass shaped frequency response of the devices already shows up in the so-called frost effect. For the design of thermo plastic devices it is important to determine the parameters limiting the transfer function. Measurements of the spatial frequency distribution of frost are compared with a first order theory of the deformation process. The agreement between theory and experiment is found to be satisfactory in view of the approximations made in the analysis.
The object of the development was to build a high performance LLTV system, for surveillance use, the only constraint being that only electrical power should be needed. The system components are the objective lens, the camera tube plus camera, the display and the laser. These are considered in turn.
This paper describes a technique used to produce high MTF phosphor screens on intagliated fiber optics substrates for use in image intensifiers. The line spread function of the intagliated phosphor screens are compared with conventional fiber optic phosphor screens. The MTF of the intagliated phosphor screen is found to approach the theoretical MTF of the fiber optics substrate by itself.
This lens was designed to have a near diffraction limited performance on axis in the long focal length configuration. Subsequent M.T.F. testing has confirmed this. Apart from the mechanical constraints, the lens presented severe design constraints to the optical designer. The range of infra-red materials available to the optical designer is limited, and the materials have a high refractive index requiring efficient anti-reflection coatings to optimize overall transmission. Blanks were interferometrically tested to ensure acceptability of internal quality prior to working into lens elements. These materials also have a high temperature coefficient of refractive index necessitating studies into methods of athermalizing the lens. A simple but effective method of achieving temperature correction, as fitted to this lens, is described.
The mechanisms of image recording with coherent and partially coherent light are well understood and many examples are to be found in the rather extensive literature. The deleterious effects in the recordings of coherent images arise from the specific functional form of the amplitude impulse response and the non-linearity of the coherent image forming and recording process. Several groups of workers have used apodisation of diffraction limited optical systems to produce acceptable amplitude impulse response functions. Satisfactory results have been obtained. Current progress in this important aspect of coherent image recording will be reviewed.
The γ-Ruticon is an erasable image buffer device that has already been described in the literature. Its imaging properties depend on three separate mechanisms. The first mechanism transforms the input image into an electrostatic charge layer (an electrostatic image). The charge layer causes a deformation of the Ruticon surface (a surface relief image). The relation between the electrostatic image and the surface relief image is controlled by the second mechanism. The third mechanism consists of the readout optical system that converts the surface relief into a conventional, output image. The total device image transfer function is derived for the case when the device is operated for optimum image fidelity. γ-Ruticons have been evaluated for displays, projection TV, coherent optical processing and scanning of color images.
Two-dimensional color pictures have been recorded as diffractive surface-relief structures in a transparent medium. They are read-out in the zero diffraction order using commercially available slide projectors or microfilm viewers. Compared to conventional color film they offer a considerable cost advantage, as they can be mass produced by hot embossing into thermoplastic sheet. Resolution up to 300 lines/mm is achieved. The pictures contain no dyes and thus cannot bleach with time or on read-out. A color picture is formed by three separate embossings sandwiched together in registration. A black and white picture requires only a single embossing.
Abstract: New preparational remedies have been found against the deterioration of ac-field-excited, resin-embedded ZnS-type electroluminescent powder layers (abbreviated EL) during operation. So far, we have been able to prepare such displays already with high visual contrast in bright ambient, with an operating voltage of only 50 V (transistor-compatible) supplied by inexpensive new oscillators, and with white emission of any desired color temperature. Now with prolonged life, the whole range of display applications, from numeric indicators up to flat TV panels, becomes accessible. For these aging studies, the author's model of EL light generation of 1963 was the starting point, leading to such improvements as aluminum coactivation plus halogen particle-growth promotion, high-pressure sulfurization to reduce copper diffusion, and surface passivation by forming inert skins around each particle to prevent surface electrolysis. These methods will help to break Lehmann's monopoly on long-life phosphors and will also provide the elusive long-life blue-emitting EL powders needed for flat TV panels.
Fifty years ago a pilot would climb into the cockpit of his aircraft, check four or five dials and take off. Today it takes a flight crew of four or five to monitor a wall of instrumentation in the cockpit of the average Jumbo Jet, as depicted in Figure 1.
Normally, the impedance of the glow discharge exploited in a d.c. plasma panel is low, and if information is to be stored in the display itself, the current in the cells must be controlled by a series resistor in each cell. Empirical studies of cell characteristics have shown the relationship between the impedance and such parameters as cell geometry, cathode material and gas composition and pressure. By suitable choice of these parameters, in particular the use of graphite as the cathode material, it was found possible to design a d.c. storage plasma panel, where the cell impedance is sufficiently high to obviate the need for a series resistor. A new theoretical model is proposed which considers the averaged field rather than the instantaenous field when deriving the ionization across the cell in the non-uniform field glow-discharge condition. The theory also takes into account losses at the cell walls and the gas density changes due to the heat dissipation in the cathode region. The model is consistent with the empirical data, and explains some of the discharge characteristics not accounted for by earlier theories. The construction and characteristics of an experimental 128 character panel with graphite cathodes operating in the storage mode is described.
F.P.S. (Focus Projection and Scan) vidicons combine the advantages of electrostatic deflection and magnetic focusing into a unique electron optics design. Recent design modifications have resulted in dramatic improvements in the areas of: limiting resolution and MTF, shading, cathode efficiency, signal handling capability and ruggedization. A new self-aligning electron gun, as well as improvements in electron optics, have combined to reduce the beam spot size to approximately six micrometers. F.P.S. tubes have been quali-fied to Mil-Std-810A (USAF) specifications. The 16 mm F.P.S. tube was recently qualified to modified Mil-Std-810B specifications which included 10 hours of both sinusoidal and random vibration at 22 g, from 50 to 2000 Hz. New F.P.S. vidicons exhibit higher beam efficiencies by virtue of their electron gun improvements. These devices require 1/3 to 1/2 the cathode current to discharge the target, and since cathode life is a primary factor in tube life, this lower current demand may be translated into longer life. Additionally, these devices will provide sufficient beam current, without spot defocusing to discharge very high signal levels at the target. Because of their ruggedness, small size and low power requirements, F.P.S. vidicons have been supplied for several U.S. military systems.
Using bismuth iron garnets it is now possible to produce magnetic bubbles in a material exhibiting a very large Faraday effect in the visible region of the spectrum. The magnetic bubbles, small cylindrical volumes of reversed magnetisation in a garnet layer, are very mobile and, as a result of the large Faraday rotation, clearly visible. Controlled generation and propagation of these mobile light spots (typically 10pm in diameter) allows the construction of patterns in which the bubble is the basic picture element. A prototype display which uses a display matrix of 36 x 36 has been made and used to display alphanumerics (capacity of 25) and simple facsimile. Although magnification is required for viewing the information (a 35 x 35 array occupies 1 mm2) a x 10 eyepiece provides good legibility of characters formed on a 7 x 10 matrix. Further properties of this novel display such as non-volatile memory, serial access and writing speed are described in conjunction with possible applications in the areas of radio communications and page composers.
Almost as soon as the properties of the laser as a light source of extraordinarily high spectral brillance became known, chemists began to speculate about its possible utility in promoting photochemical reactions with high selectivity and efficiency. Unfortunately, many of the early attempts to carry out such reactions yielded confusing results which could best be interpreted as complex thermal reactions(1). Within the past few years, however, better experiments and improved theoretical insight have revealed exciting possibilities in laser-controlled chemical reactions. We shall discuss these principles, and some examples in this presentation.
Spectroscopic results achieved through expansion cooling of the heavy molecules SF6, 238UF6, and 235UF6 are presented and discussed. The impact of these new results on the theoretical understanding of these molecules is illustrated and implications for Laser Isotope Separation by two-step photodissociation and multi-step photodissociation methods are discussed.
The reaction dynamics and mechanism of energy transfer in a gas-phase molecular collision system can be dramatically affected by an intense, external laser field. A rigorous theoretical treatment must consider explicitly the interaction of the field with the collision dynamics, where the absorption (and emission) of radiation and the molecular collision are viewed as a single process rather than separate, independent processes. The full quantum mechanical formulation yields a set of coupled equations, where the number of equations corresponds to the number of asymptotic channels (a given channel is identified by a field occupation number, vibrational, rotational, nuclear orbital angular momentum and electronic quantum numbers). A semiclassical formulation of the molecular dynamics involves the propagation of classical trajectories and their corresponding actions for nuclear motion on electronic-field potential surfaces, where each electronic-field surface depends on field-free, adiabatic electronic surfaces and radiative coupling (as functions of nuclear coordinates). Transitions between electronic-field surfaces are effected by trajectories propagating through intersection points between the surfaces analytically continued into the complex plane. Numerical results (S-matrix elements) from the quantum and semiclassical approaches have been obtained with model calculations on the process Br + H2 + hw → Br + H2.
Great care must be taken when using the laser flash photolysis technique, so as to be able to obtain accurate measurements of the quantum yield of photochemical processes and of the cross section of excited states. Due to the high light intensities required, the disturbance caused by both the exciting and the analyzing light beams to the investigated system has to be taken into consideration. The mathematical analysis of high intensity flash photolysis has been used to work out several numerical examples which serve as a basis for the discussion of published results.
A laser microfluorometer is described which is particularly suitable for the measurement of fluorescence decays in microscopic biological samples. The apparatus makes use of (1) a nitrogen pumped dye laser of special design as the excitation source, (2) a microscope system particularly suitable for fluorescence microscopy and (3) an electronic signal averager. The main properties of this instrument include high temporal resolution (~0.2 ns) and high spatial resolution (~0.5μm). This instrument is now being used to study the fluorescence properties of complexes formed by acridine dyes with deoxyribonucleic acid (DNA). Preliminary results indicate that specific information about DNA base-pair sequences and DNA microscopic structure in chromosomes can be obtained.
Historically, laser induced chemical reactions are concerned with enhancement of chemical reactions and state selection of particular reactants. Recent experiments showed that inelastic transitions in atomic collision systems can be enhanced if the collision is carried out in the presence of an intense laser field. Quantum mechanical and semi-classical treatment of molecular collisions in laser fields are discussed by George.
Overview nowadays is a very urgent need for Interactive Computer Graphics (ICG) and thus is the major intention of this paper. Rather general means of classifying ICG applications and systems are the center of the discussion while it is avoided to go too far into details. This paper sketches benefits of Graphics and especially ICG in Data Processing. Features for classifying ICG applications and systems are outlined. Today's most important ICG application types and their characteristic demands on the features of ICG systems are described. Aspects of predicting the cost/benefit ratio for ICG application are touched. Types of Software Support for general and special ICG applications are briefly discussed including an attempt to predict the future situation of ICG application. Graphic system components of today and the near future are outlined and arranged in the previously defined system of classifying features. An attempt to outline trends in ICG system design is made with regard to user's requirements and trends in technology.
This paper describes a new interactive system for treating three dimensional objects. In this system, user's hand-writing actions and their records on a sheet of paper on a graphic tablet, and displayed information on a storage type CRT with the cursor function are the main man-machine communication routes. Users need not know internal data structure of models of objects. The internal information representation of the model is constructed and processed by user's actions on the external representation of the model, its record being consulted and updated by him. Output can take various forms of representation, which are made from the internal model, according to user's needs. The outlines of the software and the special hardware used in this system are described and examples of input and output are also shown.
Fault tree graphics is an operational system that enables the user, through an intelligent graphics terminal, to construct, modify, analyze, and store fault trees. By means of this system, complex engineering designs can be analyzed. This paper discusses the system and its capabilities. Included is a brief discussion of fault tree analysis, which represents an aspect of reliability and safety modeling.
CAD/CAM systems aim to relieve designers, draftsmen and production planners of routine work by introducing data processing techniques. The CAD/CAM system described in this paper uses an interactive display for the detailing of parts, tool design and NC-programming of sheet metal parts. A description of the system is given. Based on first experiences with the interactive graphic display in this application, specifications of the required hardware and software of interactive displays are discussed.
With increasing of scale and complexity of integrated circuits the design of their mask layout becomes more and more difficult. For improving of economy and throughput time computer aids are required. Fully automated techniques have been developed and are successfully used for particular tasks but general application of algorithms is not within reach. In some IC technologies a wide range of electrical and physical constraints are to be taken into account. The experience of the designer is required. Presently known algorithms do not yield optimal solutions with respect to chip size, yet minimum chip size is a strong requirement in most cases. A partially automated way seems to be most suitable. The interactive graphical display is a qualified and powerful tool for the solution of this task. An automatically generated rough design can be detailed and finished on the screen. - The paper describes in particular the interactive part of an IC design system developed in Philips Research Lab. Special attention will be paid to several kinds of computer support during the design process. Examples are the online design rule checking facility providing minimum distances of objects, the flexible moving algorithm with rubberband like behaviour of the interconnection paths and the comparison of the layout with the given network. Interactive working will be considered as division of labour between man and computer.
Cartography has long suffered from a series of inefficiencies in its design processes. These range from the semantics of its symbology through to the mechanical processes in the eventual drawing of the map. Previous attempts at improving these processes are briefly outlined, and Interactive Computer Graphics (ICG) is seen as playing an important new role in cartography. In the University environment it is unlikely that geographers and cartographers will have dedicated systems of their own. More likely the ICG system will be shared between a number of disciplines each having common graphics requirements. The implications of this on software development are discussed.
Two large Nd-Glass lasers (C6 - P102) and a CO2 laser (M3) are currently in operation for target irradiation at the "Centre d'Etudes de Limeil". The C6 laser is a 4_arm system delivering 1 kilojoule of focusable energy in 3 nanoseconds for compression experiments. More recently, P102, a new one-beam laser, has produced 50 ps pulses in the terawatt range for interaction experiments; this laser is also our basic test bed for new laser components (soft aperture, spatial filter, disk amplifier, active mirror amplifier..). M3 is a CO2 TEA laser with 7 cm aperture final amplifier. It is capable of delivering nearly 10 joules in 1 ns for interaction experiments at 10.6 μm.