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Designing products for reduced environmental impact and improved performance requires that a diverse range of characteristics be considered. Such tradeoffs require a practicable method for combining specialized tools into an integrated analytical system. The paper describes how an integrated design tool can be constructed from modules which correspond to different aspects of the problem, such as geometry, materials and mathematical subproblems. An electronics housing design example (subject to electromagnetic, heat transfer, environmental and cost considerations) illustrates the use of the design methodology. The tool is then used to demonstrate the ability to investigate and understand interactions between different design goals.

Underwater observations of moving targets in Scotland's Loch Ness, using sonar and photographic equipment, have heightened scientific speculation that the celebrated resident monster, `Nessie', may be more than a tall tale. After centuries of myths, hoaxes, and unsubstantiated claims, there seems to be some basis for the cautious change in attitude that is taking place within the scientific community. Evidence gathered over the last decade has been largely responsible for this shift.

Nature photography was almost the first application of the electronic flash system of lighting when it became commonly available.1 Although these first units used paper capacitors charged to high voltages and discharging at microsecond rates, later ``strobes'' employed lower-voltage capacitors and operated at longer flash durations. Hence, today's conventional strobe is not suitable for the rapidly moving subjects of nature photography. This article describes a development in strobe equipment that incorporates new and improved design to create flash units of not only lighter weight, but with exposure times of less than 100 microseconds.

The Rapatronic camera takes still exposures of 2 to 20 μsec with a high degree of resolution. Exposure is easily synchronized with a fast-transient event, and the shutter has at least a 30-deg viewing angle with apertures in the useful range for high-speed photography. The shutter is of the magneto-optic “light valve” type, operating by the rotation of the plane of polarization of light traversing glass in a magnetic field (Faraday effect). Three polarizers, crossed at 0-90-0 deg, produce an open-to-closed transmission ratio in excess of thirty million, and removal of the magnetic field closes the shutter, allowing it to pass only one billionth of the light from the subject.

Waterproof cases for instruments, especially cameras, electronic flash lamps, and sonar drivers, are considered for external pressures up to 20,000 psi (pounds per square inch) which is adequate for the greatest known depths in the sea. Equations, charts, and experimentally determined values of failure are given for cylinders, end caps, and windows of various materials. Several types of pressure-resisting electric connections are shown and a pressure-testing facility is described.

Randomly distributed pulses, of any voltage shape, and of varying magnitude, actuate an amplifier whose output meter indicates only the average rate of arrival of the pulses. Counting rates of 30 per minute up to several thousand per minute are read directly from a rugged meter. The apparatus is a.c. operated, is portable, and is particularly adapted to the study of feeble gamma‐radiation. The apparatus consists essentially of a preamplifier, a uniform pulse generator based on a relaxation oscillator or on an inverter circuit, an output amplifier stage, and a capacity‐resistance electrical tank circuit for performing the averaging process.

Design details are given for two submicrosecond flash sources for photography by reflected light, silhouette and schlieren techniques. The source for reflected-light photography uses a “guided” air spark operated at 18 kv with 0.05 μf to produce a 0.4-μsec flash with a peak light of 5 million candlepower. The flashtube, a special design, is described, together with its power supply and trigger circuit. The trigger circuit can be operated by a microphone, phototube, contactor or other electrical signal, and incorporates an adjustable time delay. A photograph taken with the unit is shown. — A small spark source capable of producing flashes of about 10 mμsec duration for silhouette and schlieren photography is described. Relative peak light output and flash duration are given as a function of pressure for air, nitrogen, oxygen, carbon dioxide, hydrogen and argon. Gap resistance is given as a function of gap length, for air.

A xenon‐filled electronic flash tube with a cylindrical lighted volume of 1.2‐mm diam and 6‐mm length has been developed for use as a small source in optical systems, such as the schlieren and interferometer types. The lamp has been operated at 6000 flashes per second from a hydrogen‐thyratron driver circuit to record the density in air flow in an interferometer. Flash duration varies from 0.3 to 3 μsec, depending upon the circuit conditions. A peak brightness of 10 million candlepower per sq cm has been achieved.

An automatic stroboscopic power angle recorder developed to study directly the transient performance of synchronous machines during load disturbances is described in this paper. A portion of the machine under observation is illuminated by stroboscopic light, and its oscillations are recorded directly by a moving-film camera. The operation of the device is made automatic by connecting a suitable relay in its circuit. A typical installation on a hydroelectric generator is described.

An electronic double flash unit has been constructed to measure photographically average linear velocity of blood flow in the bulbar conjunctival vessels of the human eye. Two exposures on the same photograph separated by a predetermined time delay (adjustable from 2 to 200 msec) permit computation of velocity from the displacement of red cells per delay time. The equipment is small and mobile, the procedure innocuous.

High speed motion pictures have been found to be extremely useful in studying the motions of various types of mechanisms, especially transient high speed motions. Modern electronic devices have contributed new methods of producing accurately controlled light flashes of extremely high intensity so that now pictures may be taken by reflected light at rates up to several thousands per second.

HIGH-SPEED properly describes single exposure photographs that are taken with exposures shorter than about 1/10,000 second, and motion pictures taken at speeds above 300 pictures per second. The unaided camera, with mechanical shutter, cannot take such pictures, because of both photographic and mechanical limitations. The development by Edgerton, et al.14 of electrical apparatus for producing intermittently flashing (stroboscopic) illumination and for high-speed photography has provided a superior technic for investigating and recording rapid motion. The technic also offers advantages in "still" photography-in " stopping" motion as a result of the short duration, high intensity illumination. In addition to its ability to record and to "stop" rapid motion, highspeed photography is useful for measurement and analysis. Since in multiflash and in motion pictures the interval between flashes may be predetermined, the observer is able to record an action as a function of time. Likewise the velocity, shape, and acceleration of the

It is pointed out that the trend of modern electronic flash equipment is toward longer flash duration. After proposing a method of defining duration, an approximate method of calculating duration is given, together with resistance constants of commonly available flashtubes. Some information is given regarding the production of short flashes of light in the microsecond and submicrosecond range.

The growth of the luminous area of a high current discharge in an electronic xenon‐filled flashtube has been studied by means of a sequence of timed short‐exposure photographs taken with a magneto‐optic shutter. Electrical measurements show that the tube conductance is approximately proportional to the luminous area of the arc channel. The ionized gas has a volume conductivity of about 90 mho/cm averaged over the luminous path during the buildup for the conditions investigated.

Photoelastic photographs, with exposures of approximately one-millionth of a second, were taken of transient stresses in glass before, during, and after fracture. The longitudinal and transverse waves in glass have been photographed and their velocities measured (18,000 and 11,000 ft. per sec, respectively). It was also found that under special conditions cracks may travel slower than .5000 ft. per sec, the value previously given as the crack propagation velocity.

A grid-controlled arc-discharge tube which requires neither power nor time for heating the cathode, but in which a discharge of several hundred amperes is controlled by an extremely small amount of power in the grid circuit, is described in this paper. The tube has characteristics especially useful In circuits requiring large peak current but low average current, some examples of which are given here and is applicable particularly as a light source in stroboscopes.

By means of the “differential analyzer,” the equations describing the pulling-into-step transients of a synchronous motor can be solved readily and accurately. The results of such solutions give a rather complete analysis of pulling-into-step phenomena, and thus make possible the determination of the performance of practically any synchronous motor. Practical application of the study is illustrated by a numerical example.

The possibility of using intense intermittent light for motion pictures and special photography is discussed. Physical limitations of sources of intermittent illumination are reviewed. The characteristics of the mercury-arc thyratron which give it advantages as an intermittent light source are enumerated, viz., (1) the light is photographically actinic; (2) the duration of a light flash can be made less than ten microseconds; (3) the light intensity is high; (4) the frequency of flash is easily and accurately controlled by means of a grid. An example of the use of intense intermittent light is given, showing how stroboscopic motion pictures of the angular transients of synchronous motors are taken.

After a brief summary of the theory of electronically produced pulses of light, energy storage systems, and energy converting devices, a review is made of commonly used triggering and controlling elements. A series of practical devices utilizing the previously described methods are discussed, showing typical stroboscopes, high-speed single-flash photographic lights, high-speed motion-picture lights, and flash sequence equipment.

A synchronous motor started as an induction motor must pass through an electro-mechanical transient after the field circuit is supplied with electrical excitation in order to change its action from that of an induction motor to that of a synchronous motor. The calculation of this problem has been difficult because the differential equation of motion is of a non-linear type of which no analytical solution has been made. The integraph at the Massachusetts Institute of Technology has given a new and direct method of solving equations of the type encountered in these pulling-into-step transients. In this paper are compiled the results of many integraph solutions which were made after combining the factors that influence the performance of such machines into ratios and relative factors so that the results will apply to all practical cases. From the solutions several generalizations are made which can be directly applied to determine whether or not any type of salient-pole synchronous motor will synchronize properly. These solutions take into account inertia, saliency, incompleteness of amortisseur windings, load, switching angle, and field current, and assume negligible armature resistance, negligible rotor leakage reactance, no saturation, constant load torque near synchronous speed, and negligible electrical transients. Oscillograph tests of a 160-hp. motor and a sample calculation are given.

Using an electric spark lasting less than one-millionth second as a light source, cracks in glass have been successfully photographed during their propagation. A steel ball driven against the glass with a spring initiated fracture and simultaneously actuated an adjustable electrical time-delay circuit, which in turn set off the spark at the required instant. By the use of two sparks, the velocity of propagation of cracks in glass was found to be constant and almost exactly 5040 feet per second—the same velocity found by Schardin and Struth. In general, the tips of the cracks form a nearly perfect circle at any particular instant, though some individual photographs show nonsymmetry.

SUMMARY The use of a small-size electronic flash lamp, as a point source, makes possible a useful system for recording silhouette photographs of many subjects, such as plankton. Limitations of conventional microscopy methods, such as (1) small areas covered, (2) depth of field, and (3) subject motion, are partly overcome for some examples.

By means of moving pictures taken stroboscopically it is possible to see the rotor of a synchronous machine just as though one were actually revolving at synchronous speed with the rotating field of the stator windings. Newly developed thyratron tubes provide sufficient light for taking the pictures.

The electronic flash, strobe, or spark light sources have great ability to take photographs with short exposure. The peak light intensity must, of necessity, be very high to create an exposure in a short time.

A sub—microsecond light source was combined with recent improvements in color schlieren optics to photograph transient subjects such as bullets, air flow around propellers, and sub—microsecond electric arcs. The photographs have aesthetic merit as well as technical value. The paper summarizes color schlieren development and theory, and presents calculations for camera lens selection.

An open xenon gas spark between electrodes in a large bulb conveniently forms an intense small—volume source of light, but often shows spacial instability due to heated gas flow from previous discharges, or from electrical breakdown variations. The use of multiple inter—electrode starting wires solves the spacial problems for many applications. Information is presented on the light output, the efficiency, the spectral output, the flash duration, and the size of the emitting source as a function of time, energy, and gap length. Only lamps filled with xenon, and mostly with a small addition of hydrogen, are discussed. The experimental results were taken with 6 sizes of capacitors ranging from 0.005 to 5.6mfd. The properties of the capacitor, such as effective series resistance (ESR) and internal inductance, have been found to be very important when used with gap lamps since the arc resistance is very small.

Harold E. Edgerton was born in Fremont, Nebraska. He received the Bachelor of Science degree from the University of Nebraska in 1925. After one year with the General Electric Company, he entered the Massachusetts Institute of Technology and has been there, first as student and then as teacher, ever since. He received the .S. degree in 1927 and the hP octor of Science degree in electrical engineering four years later. At that time he was beginning his life's work, prefecting the stroboscope, which has revolutionized ultra-high-speed motion and still photography. Dr. Edgerton organized and helped in the initial operation and management of Edgerton, Germeshausen, and Grier, Inc. (EG&G). He has pioneered the development of flash photography in the ocean depths. Out of this work has grown the sonic probe of the ocean bottom. He has become widely known as an underwater explorer. Above all, Dr. Edgerton is a master teacher who understands well the meaning of relevance and the sources of motivation in education. He is a prolific contributor to scientific journals and the holder of over forty patents. He has received honorary degrees of Doctor of Engineering from the University of Nebraska, and Doctor of Laws from the University of South Carolina. A recipient of numerous awards from the foremost engineering and photographic societies of the world, he is a member of the National Academy of Sciences and the National Academy of Engineering.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Discharge lamps filled with xenon gas through which electrical capacitors are discharged have found many applications for producing pulsed energy in photography and energy discharges. The object of this paper is to review sane of the more important characteristics of flash lamps. The flash duration of specific flash lamps when operated from a given capacitor charged to same known voltage is dis-cussed below. The dimensions of the lamp are one of the most impor-tant factors since the response of the lamp to the circuit is greatly influenced. Experimentally measured flash duration as a function of capacitance and voltage is given in graphical form for one type of flash lamp. Rules (approximate) are given for converting the data into data for other flash lamps and circuits. Efficiency of a xenon lamp can be as high as 5 candela/watt for a lamp that is loaded so that the arc fills the inner diameter of the constraining tube. The life of the xenon lamp can be many, many flashes. In fact, this is one of the lamp's strong points. The spectral distribution of the light from a xenon lamp closely approximates daylight with a small shift to the blue if the applied voltage is high. Details of a specific flash lamp showing the nature of the spectral output is given. A list of some of the oractical uses of electronic flash lamps is given and discussed.

Amolitudes of high-resolution seismic reflections are reduced to within the dynamic range of facsimile profile recording by linear time-varied gain followed by 10:1 logarithmic compression so that relative amplitudes can be distinguished. The asymmetric pulse of the high-resolution Bogmer enables the polarity of isolated reflections to be determined. Seismic systems have been calibrated so that measurements of peak reflection amplitudes could be interpreted, yielding reflection coefficients of -50 to -80% in cases where no deeper penetration was observed. Presumed reduction of acoustic impedance by gas has been confirmed by samples containing gas and decomposing biologic material. These improvements to amplitude and polarity display and calibration help interpretation of biologic zones and limits to penetration on seismic profiles.

The national delegates to the 12th International Congress on High-Speed Photography, held in Toronto, Canada in 1976, were delighted to receive an invitation from the Japanese delegates to convene in Tokyo during the week of August 20, 1978. Soon, many people were making plans for their attendance and participation. Technical papers have to be written and equipment displays have to be planned. One of the real uses of an International Congress is to force the issue of a preliminary description of one's work. There is nothing like a time deadline to finish a proposed paper! It would be a very good idea to have the complete paper in hand before the summary is written, but who does it that way?

The first known photograph taken by a flash of light from an electrical discharge (spark) was accomplished about 1850 by Henry Fox-Talbot in England shortly after he invented the negative-positive process that is used so widely today. However, electrically produced flashes did not become a commonly used method until quite recently. In this article I discuss some of the exciting developments of the recent past in strobe photography, and relate some of the history that brought about this remarkable revolution in the photographic world.

All electronic flash sources have "fast," that is, "short" exposure times compared to conventional shutters. There are many users who do not realize that the effective exposure time is not the same for all flash equipments. This paper discusses the exposure time and how it is influenced by the electrical characteristics of the flash lamp, and the electrical discharge circuit. It is pointed out that the "exposure time" of many electronic flash lamps is entirely too long for some applications. The "blur" experienced in a photograph of each subject is directly due to the exposure time, and the velocity of the subject. It is obvious that photographs of people do not require as short an exposure as does the photography of a fast moving bullet. Most of the imporant factors influencing the flash-duration of electronic flash lamps will be discussed in detail. Specialized equipment for bullet and bird photography, where extra short exposure times are important, will also be described.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A method is described for photographing bats or other rapidly moving objects as they intercept in space a particular area which is covered by a camera system. Photographs taken at Carlsbad Caverns show that the tail membrane of the Mexican freetail bat is extended when the animal is in flight.

A mechanically‐improved spark gap, in an open groove along a glass or quartz rod, is described in this paper. The output is about 0.5 cps with a flash duration of less than a microsecond. The effective source size is limited by a 1.6‐mm diam. hole in an aperture plate. Ease of assembly and replacement of faulty components is the important improvement over earlier spark gaps. Mach apparently was the first to study bullets and shock waves in air with illumination from an open spark gap. A bibliography of the history of spark discharges can be found in books by Edgerton and Frungel.

Equipment is described to take double‐exposure silhouette photographs of rapidly moving objects. Each exposure time is about ⅕ microsecond, and the time interval between flashes is adjustable. An eight‐inch square Ektalite Fresnel lens is used as a field lens to focus the light from the illuminating spark into the camera lens; it is especially useful for subjects where the lens is frequently damaged.Timing of the first spark is conveniently made for explosions by a photoelectric tube triggered by the light of the explosion. A double exposure photograph of a dynamite blasting cap is given as an example.