Stroboscope
Encyclopedia
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...
, reciprocating
Reciprocation
Reciprocation may refer to:* Reciprocating motion, a type of oscillatory motion, as in the action of a reciprocating saw* Reciprocation in geometry, an operation with circles that involves transforming each point in plane into its polar line and each line in the plane into its pole...
, oscillating
Oscillation
Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...
or vibrating
Vibration
Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...
objects. Machine parts and vibrating strings are common examples.
Intense flashing/pulsing light of various frequencies can trigger epileptic seizures in people who suffer from photosensitive epilepsy
Photosensitive epilepsy
Photosensitive epilepsy is a form of epilepsy in which seizures are triggered by visual stimuli that form patterns in time or space, such as flashing lights, bold, regular patterns, or regular moving patterns.-Symptoms:...
.
Mechanical
In its simplest mechanical form, a rotating cylinder (or bowl with a raised edge) with evenly-spaced holes or slots is placed in the line of sight between the observer and the moving object. The observer looks through the holes/slots on the near and far side at the same time, with the slots/holes moving in opposite directions. When the holes/slots are aligned on opposite sides, the object is visible to the observer.Alternately, a single moving hole or slot can be used with a fixed/stationary hole or slot. The stationary hole or slot limits the light to a single viewing path and reduces glare from light passing through other parts of the moving hole/slot.
Viewing through a single line of holes/slots does not work, since the holes/slots appear to just sweep across the object without a strobe effect.
The rotational speed is adjusted so that it becomes synchronised with the movement of the observed system, which seems to slow and stop. The illusion is caused by temporal aliasing
Aliasing
In signal processing and related disciplines, aliasing refers to an effect that causes different signals to become indistinguishable when sampled...
, commonly known as the stroboscopic effect.
Electronic
In electronicElectronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
versions, the perforated disc is replaced by a lamp
Strobe light
A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope...
capable of emitting brief and rapid flashes of light. Typically a gas-discharge or solid-state lamp is used, because they are capable of emitting light nearly instantly when power is applied, and extinguishing just as fast when the power is removed.
By comparison, incandescent lamps have a brief warm-up when energized, followed by a cool-down period when power is removed. These delays result in smearing and blurring of detail of objects partially illuminated during the warm-up and cool-down periods.
The frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
of the flash is adjusted so that it is an equal to, or a unit fraction
Unit fraction
A unit fraction is a rational number written as a fraction where the numerator is one and the denominator is a positive integer. A unit fraction is therefore the reciprocal of a positive integer, 1/n...
of the object's cyclic speed, at which point the object is seen to be either stationary or moving slowly backward or forward, depending on the flash frequency.
Neon lamp
Neon lamp
A neon lamp is a miniature gas discharge lamp that typically contains neon gas at a low pressure in a glass capsule. Only a thin region adjacent to the electrodes glows in these lamps, which distinguishes them from the much longer and brighter neon tubes used for signage...
s or light emitting diodes are commonly used for low-intensity strobe applications, Neon lamps were more common before the development of solid-state electronics, but are being replaced by LEDs in most low-intensity strobe applications.
Xenon flash lamps are used for medium- and high-intensity strobe applications. Sufficiently rapid or bright flashing may require active cooling such as forced-air or water cooling to prevent the xenon flash lamp from melting.
History
Joseph Plateau of BelgiumBelgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
is generally credited with the invention of the stroboscope in 1832, when he used a disc with radial slits which he turned while viewing images on a separate rotating wheel. Plateau called his device the "Phenakistoscope
Phenakistoscope
The phenakistoscope was an early animation device that used the persistence of vision principle to create an illusion of motion.-History:...
". There was a simultaneous and independent invention of the device by the Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
n Simon von Stampfer
Simon von Stampfer
Simon Ritter von Stampfer was an Austrian mathematician, surveyor and inventor. His most famous invention is that of the stroboscopic disk which has a claim to be the first device to show moving images...
, which he named the "Stroboscope", and it is his term which is used today. The etymology is from the Greek words στρόβος - strobos, meaning "whirlpool" and σκοπεῖν - skopein, meaning "to look at".
As well as having important applications for scientific research, the earliest inventions received immediate popular success as methods for producing moving pictures
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
, and the principle was used for numerous toys. Other early pioneers employed rotating mirrors, or vibrating mirrors known as mirror galvanometer
Mirror galvanometer
thumb|right|200px|A mirror galvanometerA mirror galvanometer is a mechanical meter that senses electric current, except that instead of moving a needle, it moves a mirror. The mirror reflects a beam of light, which projects onto a meter, and acts as a long, weightless, massless pointer...
s.
In 1917, French engineer Etienne Oehmichen
Etienne Oehmichen
Étienne Oehmichen was a French engineer and helicopter designer....
patented the first electric stroboscope, building at the same time a camera capable of shooting 1,000 frames per second.
The electronic strobe light
Strobe light
A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope...
stroboscope was invented in 1931, when Harold Eugene Edgerton
Harold Eugene Edgerton
Harold Eugene "Doc" Edgerton was a professor of electrical engineering at the Massachusetts Institute of Technology...
("Doc" Edgerton) employed a flashing lamp to study machine parts in motion. General Radio
General Radio
General Radio Company was a broad-line manufacturer of electronic test equipment. Started in Cambridge, Massachusetts in 1915, the company moved to West Concord in the 1950s. There, it became a major player in the automatic test equipment business, manufacturing a line of testers for assembled...
Corporation then went on to productize this invention in the form of their "Strobotach".
Edgerton later used very short flashes of light as a means of producing still photographs
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
of fast-moving objects, such as bullets in flight.
Applications
Stroboscopes play an important role in the study of stresses on machinery in motion, and in many other forms of research. Bright stroboscopes are able to overpower ambient lighting and make stop-motion effects apparent without the need for dark ambient operating conditions.They are also used as measuring instruments for determining cyclic speed. As a timing light
Timing light
thumb|right|300px|Timing light, combination instrument with RPM, volt meter and dwell angle meter. The actual light is on the far end.The black clamp connects to the battery's -, the red clamp to +, the green one to the breaker side of the coil , the big black clamp in the foreground is an...
they are used to set the ignition
Ignition system
An ignition system is a system for igniting a fuel-air mixture. Ignition systems are well known in the field of internal combustion engines such as those used in petrol engines used to power the majority of motor vehicles, but they are also used in many other applications such as in oil-fired and...
timing
Timing
Timing is the time when something happens or the spacing of events in time. Some typical uses are:* The act of measuring the elapsed time of something or someone, often at athletic events such as swimming or running, where participants are timed with a device such as a stopwatch...
of internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
s.
In medicine, stroboscopes are used to view the vocal cords for diagnosis of conditions that have produced dysphonia
Dysphonia
Dysphonia is the medical term for disorders of the voice: an impairment in the ability to produce voice sounds using the vocal organs . Thus, dysphonia is a phonation disorder...
(hoarseness). The patient hums or speaks into a microphone
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
which in turn activates the stroboscope at either the same or a slightly different frequency. The light source and a camera are positioned by endoscopy.
Another application of the stroboscope can be seen on many gramophone
Phonograph
The phonograph record player, or gramophone is a device introduced in 1877 that has had continued common use for reproducing sound recordings, although when first developed, the phonograph was used to both record and reproduce sounds...
turntables. The edge of the platter has marks at specific intervals so that when viewed under fluorescent lighting powered at mains frequency, provided the platter is rotating at the correct speed, the marks appear to be stationary. This will not work under incandescent lighting
Incandescent light bulb
The incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...
, as incandescent bulbs don't strobe. For this reason, some turntables have a neon bulb next to the platter.
Flashing lamp
Strobe light
A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope...
strobes are also adapted for pop use, as a lighting effect for discotheques and night clubs where they give the impression of dancing in slow motion. The strobe rate of these devices is typically not very precise or very fast, because the entertainment application does not usually require a high degree of performance.
Other effects
Rapid flashing can give the illusion that white light is tinged with color, known as Fechner colorFechner color
The Fechner color effect is an illusion of color seen when looking at certain rapidly changing or moving black-and-white patterns. They are also called pattern induced flicker colors . Not everyone sees the same colors....
. Within certain ranges, the apparent color can be controlled by the frequency of the flash, but it is an illusion generated in the mind of the observer and not a real color. The Benham's top
Benham's top
Benham's top, also called Benham's disk, is named after the English toymaker Charles Benham, who, in 1895, sold a top painted with the pattern shown. When the disk is spun, arcs of pale color — called Fechner colors or pattern induced flicker colors — are visible at different places...
demonstrates the effect.
See also
- ElectrotachyscopeElectrotachyscopeThe électrotachyscope is an 1887 invention of Ottomar Anschütz of Germany which presents the illusion of motion with transparent serial photographs, chronophotographs, arranged on a spinning wheel of fortune or mandala-like glass disc, significant as a technological development in the history of...
- Flip bookFlip bookA flip book or flick book is a book with a series of pictures that vary gradually from one page to the next, so that when the pages are turned rapidly, the pictures appear to animate by simulating motion or some other change. Flip books are often illustrated books for children, but may also be...
- PhenakistoscopePhenakistoscopeThe phenakistoscope was an early animation device that used the persistence of vision principle to create an illusion of motion.-History:...
- PraxinoscopePraxinoscopeThe praxinoscope was an animation device, the successor to the zoetrope. It was invented in France in 1877 by Charles-Émile Reynaud. Like the zoetrope, it used a strip of pictures placed around the inner surface of a spinning cylinder...
- Strobe lightStrobe lightA strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope...
- Strobe tuner
- TachometerTachometerA tachometer is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute on a calibrated analogue dial, but digital displays are increasingly common...
- ThaumatropeThaumatropeA thaumatrope is a toy that was popular in Victorian times.A disk or card with a picture on each side is attached to two pieces of string. When the strings are twirled quickly between the fingers the two pictures appear to combine into a single image due to persistence of vision.The invention of...
- ZoetropeZoetropeA zoetrope is a device that produces an illusion of action from a rapid succession of static pictures. The term zoetrope is from the Greek words "ζωή – zoe", "life" and τρόπος – tropos, "turn". It may be taken to mean "wheel of life"....