The search for high gain Nd3+ laser materials has resulted in a new class of materials such as NdP014, NdLiPAO,, NdA1(B0,)A and Nd(A1,Cr)3 (BO3 )4 . The basic properties and principles of the mateflais are desctiBled: limits of concentration, fundamental rare earth spectroscopy, fluorescqnce quenching and laser action. The lasers have typical active volumes of 10-6 to 10-8° cm3 and operate at 1.06pm and 1.3pm with thresholds in the submil-liwatt range. The connection between these lasers and integrated optics is shown in terms of fundamental considerations. Epitaxial growth as well as planar waveguide structures have been demonstrated. Various examples of lasers, e.g., bulk lasers, intracavity SHG, flashlamp pumping, and LED pumping are described, illustrating the materials and the design principles. The approach of cross pumping Nd by Cr allows to improve the spectral power density by an order of magnitude. A simple sun-pumped rare earth laser device should be realizable.
For investigations of fine details of atomic energy spectra light sources are required which emit light with very well defined frequency. A powerful tunable light source is the cw dye laser. Since the frequency of a free-running laser jitters, it has to be stabilized. In order to avoid the high internal losses of a stabilization system with an intracavity electrooptic crystal, a very fast piezoelectric mirror translator has been developed. It was driven by properly designed electronics. Thus a small laser frequency bandwidth of 270 kHz rms with an output power of up to 200 mW was obtained. The laser system was tested in a sub-natural linewidth two-photon experiment with Na atoms.
The implementation of integrated optics signal processors for one dimensional signals, as for instance radar signals, is a problem attracting increasing attention. The devices in mind are miniaturized analogic processors involving Fourier transformation properties of waveguide lenses. Among different types of lenses already suggested, geodesic lenses are the one currently feasible solution when,as usual, crystal substrates with high refractive index must be used. A method for designing generalized perfect geodesic lenses has been developed by the authors. The advantage of this method is represented by the easy theoretical approach and the large flexibility in the design without requiring long computations. The employment of such lenses in integrated spectrum analyzers and two lenses correlators is discussed taking into account the characteristics of the other components of these devices, as array detectors and Bragg acousto-optic modulators. A different geodesic correlator constituted by a portion of spherical surface is also briefly described.
Information recording in conventional photothermoplastic devices (PTD's) entails charging, illumination and heat-development of the device. These three steps are examined with respect to the ultimate speed of photothermoplastic recording. It is shown that to a first order approximation the sensitivity of a PTD is proportional to the electrophotographic sensitivity Ce of the photoconductor layer. Several 'fast organic photoconductors' for use at 515 nm and 633 nm have been developed. Rapid heat development, which is largely limited by the viscoelastic properties of the thermoplastic used, has been found to be limited to the p_s-range. However, such short development times lead to overheating and therefore development times of about 100 pis are recommended for prolonged cycling. Some recent investigations are reported on a new class of PTD's developed for point storage applications. These devices operate in the 50-200 µs range and utilize photo-induced development.
The holographic storage process is investigated in LiTa03:Fe-crystals. We discuss the photorefractive principles, the physical effects determining the light-induced charge transport and the recording of volume phase holograms. The experimental results clearly demonstrate that LiTa03:Fe is a very attractive material for optical information storage.
Optical fiber communication systems are discussed from the viewpoint of practical application in the field of analog video transmission systems. Transmission characteristics of optical fiber CATV systems are described from practical experiences at Higashi Ikoma two-way optical fiber CATV field trials. Some techniques to achieve high performance of such transmission characteristics are described. Some new devices such as optical directional couplers and optical switches are examined. Video transmission experiments of multiplexing two optical signals were performed using two LED's with different wavelengths.
Optical image processing has, with a few notable and important exceptions, been overtaken by digital image processing. However, current technology in incoherent-to-coherent converters, optical detectors, and microprocessors is producing renewed interest in optical methods. Future systems will probably be combinations of optical and electronic subsystems. The current trends in this field are discussed and examples are given of present systems so that future prospects can be evaluated.
Optical distortions araising from predeflection focusing are analyzed from the point of view of laser character generators. It is shown that distortions can be kept below an acceptable limit. The advantage of multi-beam recording is analyzed and the principles of operation of a new multi-beam acousto-optic modulator are described. Using this modulator a simple laser character generator has been developed for a line printer which can work at 12,000 1pm speed.
Space laser communication involves angular tracking accuracy of the order of 10 µrad, which can be accomplished by means of an autotracking system. The main components of a system are described and test results are presented.
In this paper some fundamental parameters of sea water as a transmitting media for optical communications have been analysed. There are mean values of E (total attenuation coefficient), calculated distances for transmission of broadband information using argon laser. There are also measuring results for indirect measurements of E for two near, but different points, in Adriatic sea, and experimental results of TV signal transmission for chosen model for distances to the 30 m.
Modern spectrometry offers rich possibilities by convenient use either of interferometric devices (Fourier transform spectrometry) or of selective modulation (grid spectrometry). Progresses in resolution and luminosity have been spectacular in the last decade, and new domains of high resolution and low luminosity have been explored. In those cases of extreme performances, the instruments are generally highly sophisticated, delicate, and expensive. Nevertheless, Fourier transform spectroscopy is now developing for pratical applications. We have examined the possibilities of interferometric devices to routine spectral analysis in chemistry, biology, pollution, detection etc ... and are now aware of the interesting characteristics of those mountings by the fact that they are luminous, flexible and very simple. They need no com-puter and are very suitable for low resolutions. We shall describe first the basic principle, and later focus on the various possibilities resulting from the direct access to the interferogram and the application of the mathematical properties of the Fourier transform : Fourier derivation, Fourier correlation with a reference spectrum, Fourier correlation of derivatives etc ... Moreover when the spectrum has a quasi periodic structure a very simple interferometric device can be used and has proved to be very efficient for the detection of some atmospheric pollutants (SO2, NO2).
Today, the interpretation of spectroscopic data with the aid of time-dependent autocorrelation functions (acfs) has found widespread application to molecules in solids, liquids and dense gases. In this paper the two dominant relaxation processes influencing the acts of rotational and vibrational relaxation are reviewed. The influence of Coriolis coupling on the rotational acfs of degenerate vibrations is emphasized. Experimental acfs are discussed for the rotational relaxation of HC1 in tetrachlorides, OH- and OD- ions in single crystals of alkalihalides, gaseous chloroform and of methanes in liquid argon as well as for intramolecular vibrational relaxation in the metal carbonyls Cr(CO)6, Mo(CO )6 and W(CO)6.
Fluorescence involves the absorption and reemission of light, in which incident linearly polarised radiation is generally depolarised depending upon the directions in space of the corresponding molecular transition moments. An applied electric field imposes order on macromolecules in dilute solution and the polarised components of the fluorescence change. An apparatus is described in which the changes in the four polarised components are measured for solutions of dye-tagged nucleic acids, polymers, pigment particles and liquid crystals. Using pulsed electric fields, information on the nature of dye binding and the size of the macromolecules is obtained.
CO2 and N2 jets issuing into air from small rectangular channels of 2x25 mm cross section were investigated. Concentration measurements were obtained by cw-laser Raman spectros-copy; gradients larger than lo vol. %/100 µm could easily be resolved; spatial resolution was better than lo -2 mm3 and the measured fluctuations of the Raman signals show satisfactory agreement with Poisson statistics. Axial and radial profiles are reported for single and multiple jets and comparison with theory is given, where possible.
A mobile system for the remote measurement of polluting gases such as NO2, SO2 and HC1 has been designed and tested. The detection is based on differential absorption and scattering of infrared radiation. The essential components of the system are a deuterium fluoride laser operated in multiline mode, a 0.6 meter diameter receiver optics, monochromator, and cooled multielement detector array for the simultaneous detection of light backscattered at different frequencies. Range-sensitivity adjustment is optimized using geometrical signal compression techniques. For maximum mobility and versatility the system is mounted in a standard 20 foot container. Design characteristics and special features of the system are reported, ancillary research and development work is described, and applications are proposed.
Imaging systems incorporating X-ray image-intensifier tubes are widely used in medicine and industry. The image quality given by these systems is comparable to that given by film/intensifier screen combinations. In conventional equipment, the optical coupling system between the intensifier and the image pickup and recording system can appreciably degrade the quality of the final image. The result is reduced contrast and sensitivity, loss in resolution, particularly towards the edges of the field, and vignetting. This equipment is also bulky and heavy, and prone to change in optical alignment with time. Even using fiber-optic coupling with a special vidicon is not the perfect solution, as fiber size can limit the resolution, and dead fibers cause blemishes. In this paper, we describe a new tube in which an electron-beam scanning section, similar in design to that of a vidicon, is incorporated into the intensifier. This beam reads out the charge-pattern image that is created on a silicon target by the photoelectrons. With this tube, doses on the order of 1 to 4 btR per image, and 100 to 300 µR per image are required for fluoroscopic and fluoro-graphic operation respectively. The limiting spatial resolution (5 % modulation), obtained by measurements with bar charts, is 32 lp.cm-1.
The investigation of the image-quality determining sections of the X-ray TV chain is an important matter for the optimization of the whole system. The modulation-transfer functions (MTF) of each component as the most important factor for the evaluation of the separate sections of the X-ray chain were measured. Special attention was given to gain exact measurements of MTF and other behavior of image pick-up tubes. In the second part of this paper image-quality determining factors and development tendencies of appropriate video stores for high resolution are discussed.
A digital image processing facility is being installed at the University of Arizona to serve the needs of clinical practice and research for improved imaging and diagnosis from radiology. In addition, this facility will support similar needs from other image generating services throughout diagnostic medicine that use ultrasonic devices, gamma cameras, and thermography. Attention is drawn to the structure of this system and its design for dealing with the most severe problems facing diagnostic radiology. These include the input of radiological images to a digital computer, storage, and display. Possible solutions are discussed in terms of utility, performance, economics, and acceptance by the diagnostic radiologist.
Photofluorographic cameras or the Odelca type have been widely used ror more than 25 years in mass chest x-ray examination. Such cameras provide full diagnostic detail on a reduced size low cost photograph, but although they are equipped with extremely wide aperture optics, the required x-ray dose is somewhat higher than that for a full size radiograph. This disadvantage, which has limited the range of application of photofluorography in the past, is eliminated in the new Oldelft "Electrodelca". This camera includes an electro-optical image intensifier of the proximity focussed type, the output of which is fiberoptically coupled to the photographic film. The design criteria for this approach are discussed and performance data are presented.
This new video recorder - the Videographe - provides the capability for transferring television images directly onto a photosensitive dry-processed paper. This laser recorder produces, with standard composite video signal, immediately visible recording with both high contrast and resolution (sixteen grey shades, 750 lines, 625 spots per line) in less than 35 seconds and in large dimensions (2] cm x 30 cm). This recorder will be very useful for medical applications (ultrasonic, X rays, thermal and nuclear imaging) giving immediate high quality and large dimensions images.
The use of lasers in clinical routine work of ophthalmology is known up to now only for retinal coagulation. I would like to present another application of the laser in Ophthalmology as a diagnostic tool.
A device that measures the hot rolled strips or plates shape was developed by the Irsid, in collaboration with the frim Delta, with the Ministry of Industry financial help. It uses new technics: photodiodes areas for the sensor, a microprocessor unit for the signal processing. An industrial prototype is set up on the hot rolling mill of the firm SOLMER at Fos-sur-Mer. It will allow to take up a new stage in the flat products rolling leading.
This paper describes some general features of a computer-controlled laser system for noncontact measurements of dimensions of objects. The laser beams are scanned over the object and a system of detectors mounted behind the object detects whether the beams are shadowed by the object or not. The detector signals are converted to digital values and transferred to a minicomputer, where they are processed. This may require special software to allow the dimensional data to be presented in real time. An experimental system with a HeNe laser and controlled by an HP 21MX minicomputer has been built and tested. At a rate of 100 measurements per second the systematic error is in the order of 1 mm for absolute measurements and 0.1 mm for relative measurements. The imprecision is about 0.1 mm for both cases.
In optical methods of stress analysis, the reduction of raw data to engineering quantities has proved to be a difficult problem. A portable instrument has been developed which interrogates a specimen grid point-wise using a narrow beam of coherent light, and electro-optically measures interference-fringe-spacing, in three directions simultaneously. A microprocessor is incorporated to convert the strain component values to convenient quantities such as principal stress and shear, and these are displayed. The read-rate is adjustable up to 5 kHz, the discrimination level is 4 µε, and a facility for temperature compensation is included. The logic behind the design of the major features of the unit are described.
This paper describes a novel method of stress determination in structures under dynamic loading conditions. The principle is based on the thermodynamic property of a material in which, under adiabatic conditions, heat is produced or absorbed in direct proportion to the magnitude of the stresses to which it is being subjected. An instrument is described which uses infra-red radiation to measure, remotely, the resulting minute local temperature changes in the material, with oscillating mirrors to provide a raster type scan of the item under test. Spatial resolution down to 1 mm and a temperature discrimination of about 0.002 00 have been achieved, this latter representing a stress change of less than 300 lb/in2 in steel. Results are given which demonstrate the ease with which the equipment can be used to assist in the design of a structure and an indication is given of its potential value in the field of Non-Destructive Testing, for example in the location of fatigue cracks.
A new electro-optical technique has been exploited in devices of high performance for the comparative metrology of certain features of small mechanical components. The technique and the devices are described and typical performance figures given.
In laser velocimetry, flow velocities are deduced from the frequency of the light scattered by microparticles transported by the flow and seen through a fringe pattern. This frequency being independent of the sign of the velocity, this sign can be determined by moving the fringe pattern : this operation makes use of acousto-optical modulators which change the frequency of the laser beams interfering in the probe volume. A general discussion of this method compared to other possibilities is given in this paper.
This paper gives design considerations for a new MTF machine (ODETA V). The new machine measures optics, but most important feature is rapid MTF measurement of low light level devices like Image Intensifier Tubes. Photon and Detector noise are of paramount importance. A variety of MTF measuring methods is evaluated for noise. They include TV pickup tubes and self scanning photo detector arrays, slit scanning of the line spread function and mask scan methods: Pseudo Noise masks, Hadamard and Moire Sine Wave masks. A new Moire pattern generator is shown. New ODETA V is a programmable MTF machine. It provides a complete MTF read out on CRT (for focussing), X-Y recorder and digital printer. Scan speed (photon integration) is variable in a 20 to 1 range for optimum noise. Single frequency read out can be programmed at up to 5 user selectable frequencies. In this mode very few photons are wasted on the unwanted intervening frequencies. A PTF module is available as an optional extra. Phase is believed to be not really necessary for Image Quality Assessment. It is shown that phase (PTF) is not independent of amplitude. Constraints exist. An ideal MTF precludes bad phase response.
The supply of germanium has been of major concern to industry who utilize it in numerous applications. One application, Electro-Optics Viewing Systems, use the unique optical properties of germanium to operate within a given spectral range. Similarly, germanium is used in such semiconductor devices as radiation detectors, light emitting diodes, and solar cells. The oxide of germanium is used in the textile industries of Europe and Asia as a catalyst. For these commodities, there is a predictable increase in demand for both non-military and military use in the 1980's. The impact of this increase in demand is evaluated and compared with its supply.
High power CO2 Lasers are currently being used for various engineering applications such as welding, drilling, cutting, transformation hardening, surface alloying, cllading and glazing. It is the purpose of the presented paper to describe some aspects of the cutting application. The Laser as a cutting tool is described from both the system and the process points of view. The characteristics and performences of some typical Laser machining systems are described and a survey on the state of the art of Laser machining systems offered by various manufacturers is presented. Recent results of a study on metals cutting by a CO9 Laser are presented. The workpieces materials are Low Carbon Steel (AISI 1045), Stainless Steel (AISI 314L), Ti6A14V and Inconnel 718. The most significant tnetallurical transformations have observed in the Low Carbon Steel, thus, in comparison to the Stailess Steel, wherin the only observed damage phenomena are crakes and intergranular etching. In the H.A.Z. of the Titanium alloy the microstructure changes from a and IS phases to a martensitic phase (a') accompanied by the disappearance of the IS phase. In the H.A.Z. of the Inconnel an increase of the hardness and microcracks have been found although no microstructure change can be observed.
The availability of high power cw carbon dioxide lasers with sufficient ruggedness, reliability and simplicity of operation for use in manufacturing facilities has led to the development of new machining methods. These methods currently involve the localized vaporization or melting of the material due to beam heating. (1) In the case of metallic materials beam heating is supplemented with burning enhanced by a flow of oxidizing gases at the point of impingement of the laser beam. In our research, we have developed a new and dif-ferent method of cutting with a laser, laser assisted hot spot machining (LAM), in which the laser is used to heat the volume of material directly in front of a single point cutting tool to a temperature less than its melting point.(2,3)The application of gas torch and induction heating to assist, in the turning of metals was first studied in the United States by Tour and Fletche(1949). Concurrently, Schmidt investigated the use of gas torch heating in milling. Although many advantages were reported such as reduction in power consumption tool life improvement and improvement in surface finish, hot-machining has not been perceived as a practical and economically viable method by industry. Recently, however, with the development of more intense heat sources such as the plasma-arc(5) and the laser, hot machining has become more attractive in specific applications as a metal removal technique.
The multikilowatt continuous carbon dioxide laser is an efficient, compact and robust system which meets many metalworking requirements. A brief account is given of important principles and characteristics of a range of lasers of this type developed at the UKAEA Culham Laboratory, and techniques are described for their use in welding and surface treatment operations. The underlying principles of these processes are summarised and results are presented which highlight the areas of manufacturing technology for which they are particularly suited.
Scope of this paper is to give an overview of the activities developed in the CRF laser laboratory equipped with a 15 kW CO2 laser source. These activities are focused on the development of processing opportunities regarding transport vehicles as well as turbine and diesel engines. Four examples are discussed: surface transformation hardening, surface alloying, wear resistant coating and hot corrosion resistance coating.
This paper describes the absorption of 'laser light' by a workpiece and shows that the physical, chemical and thermal changes that result, can be controlled, to cause either drilling or welding of the workpiece. The subject is treated from a practical engineering/applications viewpoint and includes case studies of established industrial applications. The unique features of laser processing are highlighted and where appropriate, comparisons are made with other industrial processes.
The possibility of producing laser welds by the so called "deep" penetration welding mechanism similar to the well established electron beam welding technique has been known for almost ten years. However, unlike electron beam welding, the beam metal interaction mechanisms can have a serious effect on the weld depths achieved in a single pass. The relevant laser process and material parameters will be discussed in terms of their effect on welding performance and compared with other welding methods.