Dictionary:
stro·bo·scope (strō'bə-skōp')  |
[Greek strobos, a whirling + -SCOPE.]
stroboscopic stro'bo·scop'ic (-skŏp'ĭk) adj.| 5min Related Video: stroboscope |
| Britannica Concise Encyclopedia: stroboscope |
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| Sci-Tech Encyclopedia: Stroboscope |
An instrument for observing moving bodies by making them visible intermittently and thereby giving them the optical illusion of being stationary. A stroboscope may operate by illuminating the object with brilliant flashes of light or by imposing an intermittent shutter between the viewer and the object.
Stroboscopes are used to measure the speed of rotation or frequency of vibration of a mechanical part or system. They have the advantage over other instruments of not loading or disturbing the equipment under test. Mechanical equipment may be observed under actual operating conditions with the aid of stroboscopes. Parasitic oscillations, flaws, and unwanted distortion at high speeds are readily detected.
The flashing-light stroboscopes employ gas discharge tubes to provide a brilliant light source of very short duration. Tubes may vary from neon glow lamps, when very little light output is required, to special stroboscope tubes capable of producing flashes of several hundred thousand candlepower with a duration of only a few millionths of a second. See also Neon glow lamp; Vapor lamp.
| Columbia Encyclopedia: stroboscope |
If the stroboscope is not quite synchronized with the object's motion, the object will appear to move slowly either backward or forward, depending upon whether the stroboscope's rotation is too fast or too slow. For more accurate observation a flashing light (stroboscopic light) is used instead of a disk. When used in conjunction with a camera a stroboscopic light can also be used to study motion that is not cyclic, e.g., a speeding bullet; the resulting photograph shows a series of still images whose separations are proportional to the object's speed.
The stroboscope was invented and improved upon by H. E. Edgerton starting in 1931. It has various uses in scientific research, teaching, and industry, where it is used to study stresses on parts of machines while in motion.
Bibliography
H. Edgerton et al., Stopping Time: The Photographs of Harold Edgerton (1987).
| Occultism & Parapsychology Encyclopedia: Stroboscopes |
Devices that create light pulsations at intervals varying from one flash every few seconds to several flashes per second. They have become a familiar part of the atmosphere of excitement at some dance halls and discotheques, but in different situations they have proved of some assistance in inducing hallucinatory experiences, especially when seen with half-open or even closed eyes.
Pierre Janet did pioneering work with stroboscopes. He flashed lights at mental patients and saw some immediate breakthroughs in their health. The strobes work by a process called entrainment, in which the brain tends to align itself with the frequency of the flashing light. A beam flashed at the right frequency can induce a more relaxed state and cause the brain to change its frequency.
Sources:
Hooper, Judith, and Dick Teresi. Would the Buddha Wear a Walkman? New York: Simon and Schuster, 1990.
| Wikipedia: Stroboscope |
A stroboscope, also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. The principle is used for the study of rotating, reciprocating, oscillating or vibrating objects. Machine parts and vibrating strings are common examples.
In its simplest form, a rotating disc with evenly-spaced holes is placed in the line of sight between the observer and the moving object. The rotational speed of the disc 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, commonly known as the stroboscopic effect.
In electronic versions, the perforated disc is replaced by a lamp capable of emitting brief and rapid flashes of light. The frequency of the flash is adjusted so that it is an equal to, or a unit fraction below or above the object's cyclic speed, at which point the object is seen to be either stationary or moving backward or forward, depending on the flash frequency.
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Joseph Plateau of Belgium 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". There was a simultaneous and independent invention of the device by the Austrian Simon von Stampfer, 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, and the principle was used for numerous toys.
Other early pioneers employed rotating or vibrating mirrors. The electronic strobe light stroboscope was invented in 1931, when Harold Eugene Edgerton ("Doc" Edgerton) employed a flashing lamp to study machine parts in motion. General Radio 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 of fast-moving objects, such as bullets in flight.
Stroboscopes play an important role in the study of stresses on machinery in motion, and in many other forms of research. They are also used as measuring instruments for determining cyclic speed.
As a timing light they are used to set the ignition timing of internal combustion engines.
In medicine, stroboscopes are used to view the vocal cords for diagnosis of conditions that have produced dysphonia (hoarseness). The patient hums or speaks into a microphone 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 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, as incandescent bulbs don't strobe. For this reason, some turntables have a neon bulb next to the platter.
Flashing lamp 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.
A strobe light is also used in some alarm systems to give a visual warning for people who may be hard of hearing and cannot hear the alarm bell.
Rapid flashing can give the illusion that white light is tinged with colour, known as Fechner colour. Within certain ranges, the apparent colour 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 colour. The Benham's top demonstrates the effect.
At certain frequencies, flashing light can trigger epileptic seizures in some people.
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved. Read more |
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| Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/. Read more |
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| Occultism & Parapsychology Encyclopedia. Encyclopedia of Occultism and Parapsychology. Copyright © 2001 by The Gale Group, Inc. All rights reserved. Read more |
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| Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Stroboscope". Read more |
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