A STROBOSCOPE also known as a STROBE, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. It consists of either a rotating disk with slots or holes or a lamp such as a flashtube which produces brief repetitive flashes of light. Usually the rate of the stroboscope is adjustable to different frequencies. When a rotating or vibrating object is observed with the stroboscope at its vibration frequency (or a submultiple of it), it appears stationary. Thus stroboscopes are also used to measure frequency.
The principle is used for the study of rotating , reciprocating , oscillating or vibrating objects. Machine parts and vibrating strings are common examples. A stroboscope used to set the ignition timing of internal combustion engines is called a timing light .
* 1 Types
* 1.1 Mechanical * 1.2 Electronic
* 2 History * 3 Applications * 4 Other effects * 5 See also * 6 References * 7 External links
In its simplest mechanical form, a rotating cylinder (or bowl with a raised edge) with evenly spaced holes or slots 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 , 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. 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. For most applications, incandescent lamps are too slow for clear stroboscopic effects. Yet when operated from an AC source they are mostly fast enough to cause audible hum (at double mains frequency) on optical audio playback such as on film projection.
The frequency of the flash is adjusted so that it is an equal to, or a unit fraction 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 lamps 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.
1540 Strobolume, a professional grade stroboscope produced by General Radio Close-up view of the 1540 Strobolume control box
Joseph Plateau of
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 mirrors, or vibrating mirrors known as mirror galvanometers .
In 1917, French engineer Etienne Oehmichen patented the first electric stroboscope, building at the same time a camera capable of shooting 1,000 frames per second.
The electronic strobe light stroboscope was invented in 1931, when
Harold Eugene Edgerton