Edgerton H

Harold E. Edgerton was inventor who developed the strobe light and

multiflash photography, and who thereby revolutionized the art of picture

taking in the C20th. He held over 40 patents for inventions related to

"seeing the unseen", including high-speed camera equipment, sonar probes,

and under-water lighting devices. Although greatly admired in engineering

circles for his inventions, is best known by the public for his photographs

• high-speed techniques he developed made it possible for him to freeze

action of such things as a bullet passing through an apple and a drop of

milk as it splashes and forms a coronet.

Edgerton born in 1903 at Fremont, Nebraska. One of his early childhood

memories was of designing and building a searchlight for the porch of his

house at age of 10 - had thus already begun to experiment with the way in

which optics control beams of light. As a child, Edgerton moved several

times during first 12 yrs of his life before settling in Aurora, Nebraska,

where while in junior high school he bought his first camera, a

postcard-folding Kodak. An uncle from Iowa had kindled interest in

photography, and Edgerton then set up darkroom in his mother's kitchen: with

his first camera he had hoped to photograph a ham radio station he had

assembled, but expectations were soon tempered by reality of lighting

problems - most of his early photographs were similarly badly underexposed,

and he began during his teens to explore existing methods for illuminating

photographic subjects. By the mid-1920s, he would combine his knowledge of

photographic illumination with another keen interest, electric engines.

During his summers, Edgerton worked for the Nebraska Power and Light Co. in

Aurora, where he was introduced to the problems engineers faced when

attempting to diagnose malfunctioning generators in motion. In 1925 he

completed his B.Sc. in electrical engineering at the University of Nebraska,

and then took a job with the General Electric Company in Schenectady, New

York, analyzing the performance of large rotating motors. A year later

(1926) he enrolled in the graduate programme in electrical engineering at

MIT, and - following on from his work experience - began a study to analyze

the performance of large rotating motors and in particular the action of

rotors inside electrical engines. Was particularly interested in what is

known as "power system stability" - the ability of synchronous electrical

generators and motors to stay in step after sudden disturbances such as

lightning strokes hitting transmission lines.

A synchronous motor is one whose spinning speed is proportional to the beat

of electrical current that drives its rotor - i.e. the rotational speed of

the driven rotor is synchronous with the frequency of the driving current,

so that if e.g. magnetic field created by alternating current coursing

through the motor's armature rotates at rate of 60 times per second, the

fixed magnetic field fo the rotor will "latch on" to the rotating armature

field thereby causing the rotor also to turn at 60 revolutions per second.

One problem with this type of motor, however, is that, upon starting, the

electrically created armature magnetic field is at full speed instantly, but

the rotor cannot accelerate that fast, or even get started by itself - thus

special provisions (differential electrical connections, separate starting

motors, etc.) are necessary to get the rotor up to near synchronous speed so

that the very tricky operation of snapping into synchronism can be

accomplished. Exactly when and how switching to synchronous operation should

happen, and effects of mechanical load variation were the subjects of

Edgerton's research.

While researching subject of synchronous motors in MIT's Vail Library,

Edgerton decided that an early analogue computational device called the

Bush-Hazen integraph (invented by MIT's Vannevar Bush and Harold Hazen)

could be used to study the subject of abrupt change of load on a synchronous

machine. His research (published 1930) showed that applying a load slowly

was the most efficient method of easing a motor into synchronism, but this

work involved highly complex calculations, and meanwhile E. thought would be

even better to study the phenomenon visually.

N.B. From this point there are 2 versions of story:

i) As part of this study, Edgerton had had to determine accurately the

transient changes in the angular displacement of the rotor of a synchronous

electric motor, but these displacements in the speeding rotor could not be

seen with the naked eye. One method E. tried (in late 1927) was use of

mercury arc rectifiers to supply very fast reinforcement to a powerless

generator. During the course of the experiment, E. suddenly realized that he

could see the rotating poles of the machine oscillate about a mid-position

following a simulated system disturbance. The mercury arc rectifiers

happened to be placed close enough to the generator for their flashes to

illuminate its rotor stroboscopically, and E. immediately recognized the

opportunity to develop a "stroboscope" for the purpose of "stopping motion"

and he proceeded to develop the first modern stroboscope. (Stroboscope - or

use of a short duration electric spark flash for visual observation of

fast-moving objects - first suggested by Sir Charles Wheatstone in 1833;

idea also explored by Faraday, and then by Belgian Joseph Plateau and

Austrian Simon Stampher, who both constructed working stroboscopes for

public display - led to modern motion picture).

ii) Idea was that if E. could control a light that flashed at a speed

matching that of the engine's rotation, he could make the rotors appear to

stand still. In late 1927, E. began experimenting with his first flashing

light machine, or stroboscope, to capture the action of the rotor blades,

for which he used several unconnected elements that were scattered around

his lab. One of these was instrument he had been using at that time for

taking voltage measurements that had as part of its circuit a thyratron - a

glass-filled tube that produces short bursts of light when energized with

pulses of electrical current. To keep the tube cool while he took his

measurements, E. had placed an electric fan on his bench and, glancing up,

he noticed that the flashing light of the thyratron was acting as a

stroboscope, illuminating the individual blades of the whirling fan and

making them appear to rotate slowly backwards.

Which story true, is not clear when exactly E. decided to use strobscopic

light to examine the turning rotor of a synchronous motor, but when in 1929

he suggested that for his master's thesis, his student Kenneth Beardsley (E.

started teaching at MIT in 1928), should examine various kinds of

stroboscopes then available, and add third element of photography to the

stroboscope/motor system. This not a new idea (though E. might not have been

aware of this), as in Frnace the Seguin Brothers were then marketing an

electronic stroboscopic flash unit - though their company would soon go out

of business, while E.'s invention would capture public imagination - partly

cos of E.'s own visionary faculty.

During 1929-30, Beardsley took some acceptable pictures with a Cooper-Hewitt

mercury lamp that he caused to flash using a mechanical switch, but this

system not useful for E.'s purposes, so in 1930 E. once again took up the

mercury thyratron as his light source, which could emit 60 10-microsecond

flashes per second when hooked up to a 60Hz source. He then took a thyratron

to the MIT Dynamo Lab and attached 2 cardboard bands, marked N and S, to the

poles of the synchronous motor - when the rotor achieved full speed (about

95 mph on circumference) the cards seemed to stand still when viewed in the

flashes of the mercury thyratron strobe. These photos were then used by

young graduate student Paul Fourmarier, who had also been studying

synchronous motors and had worked out the complicated intergraph

calculations that described what happened when the motor was pulled into

synchronism as the direct current used by armature was switched on -

Fourmarier read his paper in Jan 1931 at meeting of American Institute of

Electrical Engineers, and with E.'s approval exhibited compelling visual

evidence to back up his calculations - a motion picture taken by E. using

the thyratron stroboscope as a light source, so that engineers could

actually see what F. had figured out - as the pulling-into-step sequence

began, the poles of the motor appeared to be rotating backwards and to be

slowing down; then the direct current field was activated, and suddenly the

poles gave the illusion of jumping ahead, then vibrating back and forth over

a single position; finally, pulling completely into step, they appeared to

sto and stand perfectly still - showing they had reached synchronicity:

rotational speed of the armature matched the frequency of the alternating

current, which matched the flashing speed of the stroboscope.

Vannevar Bush v. impressed by E.'s stroboscope, and in 1931, when E.

received his doctorate from MIT - for his study of the "Benefits of

Angular-Controlled Field Switching on the Pulling-into-Step Ability of

Salient-Pole Synchronous Motors" - he included a motion picture made with a

mercury-arc stroboscope that he had developed with another of his students,

Alfred McClure. Meanwhile, E. had already begun considering the commercial

possibilities of the stroboscope, and got permission from Bush to file for a

patent in his own name - and he then formed commercial partnership with his

unpaid research assistant, former student Kenneth Germeshausen to develop

the device. One of Edgerton & Germeshausen's first jobs was at the Lever

Bros factory next door to MIT campus: Lever Bros then being sued by Proctor

& Gamble on claim of infringement of patented method of popping soap apart

until it formed a fine powder. E&G were asked to take high-speed motion

pictures of the process in order to provide visual proof that the Lever

Bros' methods were significantly different to those of Proctor & Gamble,

which they did. Camera they used designed by another of E.' students,

Herbert Grier, for his thesis - when movies proving Lever Bros claim were

exhibited, Proctor & Gamble dropped the suit.

E. filed for first patent in 1933, and yr later - with patent pending (wd

prove v. complicated and costly), he agreed deal with General Radio Co. for

manufacture and sale of E.'s mercury-arc stroboscopes, while during summer

1934 he and his family took stroboscope across the US demonstrating it to

factory managers, creating first demand.

Introduced for industrial use in 1934, the strobe soon became an essential

analytical tool: was employed in factories to analyze the revolution rate of

high-speed revolving machinery and had especially important textile and

automotive industry applications. Following invention of the stroboscope, E.

went on to develop high-speed cameras. He collaborated with 2 colleagues,

Kenneth Germeshausen and Herbert E. Grier, and together they produced an

electrical contactor that made it possible to synchronize a flashing light

with film as it moved through a motion picture camera. By 1934 it was

possible with their technology to photograph 6,000 frames per second (normal

speed of film through camera is 24 frames per second). During late 1930s,

were then approached by A.G. Spaulding, manufacturer of sporting goods, to

use high-speed photography, both still and motion, to study the dynamic

behaviour of its baseball bats, tennis rackets, golf clubs, and balls.

Xenon: E's first manufactured stroboscopes (from 1933-34, known as the

Strobotac) contained gas discharge tubes that emitted light when subjected

to high voltage pulses - ie light is produced by an electric spark inside a

gas-filled lamp; electricity flows into a kind of electrical reservoir known

as a condenser, and when the reservoir is full, it overflows at the desired

instant to produce a brilliant flash (has been called a bolt of "miniature

lightning") inside the lamp. First flash photography etc. Although tube in

E.'s first machines contained mercury vapour, eventually, after trying many

different gases, during 1930s Germeshausen - whose job this research was -

began using rare gases argon (which gave a bluish light) and krypton (which

gave a reddish or greenish light). Later, during the 1940s, Germeshausen

then started using xenon, as gave a light extraordinarily like sunlight -

and other rare gases were the most effective at producing very bright light.

(Just says he came to this via trial and error, knowing about flashes from

rare gases disc. 1898). Stroboscope E. produced as safe and reliable, a

welcome replacement for the explosive and difficult to control flash powders

and chemical flashbulbs used by early C20th photographers to produce rapid

bursts of light. By 1931, his strobe was capable of producing an

intermittent light that flashed repeatedly, on command of the operator, at

one-millionth of a second. (Human eye blinks at one-fortieth of a second).

E. applied for patent in 1933, but was not granted cos of litigation til

1949.

EG&G's invention revolutionized cinematography, and in 1940 three went to

Hollywood to demonstrate high-speed cinematography to MGM studios, where he

collaborated on an Academy Award-winning short, 'Quicker Than a Wink' - film

contained all now classic Edgerton shots, including a golfer driving a ball

through a telephone book, and some of the first milk-drop splashes. From

1834, seems that Germeshausen responsible for scientific research, Grier

responsible for engineering and design of equipment, and E. for PR and

liaison between MIT, industry and EG&G, plus initiating many of the new

applications of the new improved stroboscope - was he who had vision to see

extraordinarily varied and wide application of this invention.

Meanwhile, in 1939, the U.S. Army Air Force commissioned E. to design a

strobe lamp for use in nighttime aerial photography. During WWII, E.'s lamp

was first employed on reconnaissance missions in Normandy to assess German

presence before D-Day invasion - E. designed and tested powerful flash units

that were mounted on reconnaissance planes and used to photograph activities

of enemy troops after dark. E. was then sent to Italy, where initially he

trained two planes and crews which then flew some 80 missions studying how

the Germans were renewing their ammunition supplies to their positions as

the Allies sought to speed up the German retreat up the Italian peninsular.

After this successful 3-month operation, E. was then transferred to England

(1944), where he built a reconnaissance squadron which used both his light

and camera systems all over land in Europe and also in submarine searches.

Major problem E. came across in England was with the very best fighter

pilots, who objected to "just running cameras around" when had been trained

to fly fighters and shoot down bombers - to encourage these pilots, he

discovered coordinates (does not say how) of a nudist camp in England and

surreptitiously targeted it, along with variety of other targets, for

training missions. Ploy, according to E., worked well - pilots were amazed

by clarity of the photographs, and grew to enjoy and appreciate importance

of their job. Once developed, during 1944-45, the E. reconnaissance system

yielded valuable info re German troop movements on the Continent - e.g. when

Patton and Bradley were making some of thier great advances through France,

intelligence plus reconnaissance data from E.'s night photography indicated

that there were no German forces in their way at critical places. Success of

flash photography in European theatre led to use of E.'s system in the

Pacific in 1945 - for his war work, E. was awarded the Medal of Freedom in

1946.

After war, E. and his 2 collaborators formed company named Edgerton,

Germeshausen and Grier (EG&G, 1947). Soon afterwards, EG&G was awarded a

contract by the Atomic Energy Commission to photograph nuclear weapons tests

• of first atom bombs, and first hydrogen bomb - and in 1950 the company

designed a camera shutter that had no moving mechanical parts, opening the

way for high-speed still photography at exposure times as short as one

ten-millionth of a second.

In 1953, the National Geographic Society sponsored research by E. on

underwater electronic flashtubes and camera equipment. That yr, E. began

what became lifelong association with French undersea explorer Jacques

Cousteau - 2 men travelled together aboard the 'Calypso', Cousteau's

research vessel, on expeditions that explored the Mediterranean, Lake

Titicaca in Andes, and the Caribbean. E. developed underwater lighting

equipment and sonar scanners for Cousteau, as well as for the Woods Hole

Oceanographic Institution and other exploration teams. In 1961, he created a

sonar device that could generate a continuous seismic profile of the ocean

floor. In 1968, with aid of his sonar technology, explorers located the

'Mary Rose', a sunken English warship from time of Henry VIII, and in 1973

E. himself joined successful expedition to locate the USS 'Monitor', a Civil

War battleship (first US iron-clad gun boat) sunk in 1862 off Cape Hatteras,

North Carolina. Two years later, with Cousteau, E. located the HMS

'Britannic', twin ship of the 'Titanic', and in 1972 and 1976 he accompanied

a team on an unsuccessful search for the Loch Ness monster in Scotland. His

Edgerton-Benthos camera was used in 1986 to photograph the sunken 'Titanic',

found off the shore of Nova Scotia.