Retroreflectors are clearly visible in a pair of bicycle shoes. Light source is a flash a few centimeters above camera lens. A retroreflector is a device that sends light or other radiation back where it came from regardless of the angle of incidence, unlike a mirror, which does that only if the mirror is exactly perpendicular to the light beam. Image File history File linksMetadata Download high resolution version (1486x968, 809 KB) Summary A pair of bicycle shoes with reflectors visible. ...
Image File history File linksMetadata Download high resolution version (1486x968, 809 KB) Summary A pair of bicycle shoes with reflectors visible. ...
This article or section does not cite any references or sources. ...
Fig. ...
A mirror, reflecting a vase. ...
Types of retroreflectors Retroreflection is usually obtained in one of two ways: - with a set of three mutually perpendicular mirrors which form a corner (a corner reflector or corner cube), and
- with reflecting and refracting optical elements arranged so that the focal surface of the refractive element coincides with the reflective surface, typically a transparent sphere and a spherical mirror - this same effect may be achieved with a single transparent sphere provided that the refractive index of the material is exactly two times the refractive index of the medium from which the radiation is incident. In that case, the sphere surface behaves as a concave spherical mirror with the required curvature for retroreflection. This is conventionally known as a cat's eye retroreflector in either configuration.
The term cat's eye derives from the resemblance of the cat's eye retroreflector to the optical system that produces the well-known phenomenon of "glowing eyes" in cats and many other vertebrates (which are of course only reflecting light, rather than actually glowing). The combination of the eye's lens and the aqueous humor form the refractive converging system, while the tapetum lucidum behind the retina forms the spherical concave mirror. Because the function of the eye is to form an image on the retina, an eye focused on a distant object has a focal surface that approximately follows the reflective tapetum lucidum structure, which is the condition required to form a good retroreflection. Buoy in San Diego Harbor. ...
Transparent glass ball In optics, transparency is the property of allowing light to pass. ...
Transparent glass ball In optics, transparency is the property of allowing light to pass. ...
The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ...
A regular white cats eye of the kind invented by Shaw, marking the middle of the road. ...
Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ...
The aqueous humour is the clear, watery fluid that fills the complex space in the front of the eye which is bounded at the front by the cornea and at the rear by the front surface or face of the vitreous humour. ...
tapetum lucidum in a calf eye, with the retina hanging down The tapetum lucidum (Latin: bright carpet) is a reflecting layer immediately behind, and sometimes within, the retina of the eye of many vertebrates (though not humans); it serves to reflect light back to the retina, increasing the quantity of...
Human eye cross-sectional view. ...
tapetum lucidum in a calf eye, with the retina hanging down The tapetum lucidum (Latin: bright carpet) is a reflecting layer immediately behind, and sometimes within, the retina of the eye of many vertebrates (though not humans); it serves to reflect light back to the retina, increasing the quantity of...
Corner retroreflectors occur in two varieties. In the more common form, the corner is literally the truncated corner of a cube of transparent material such as conventional optical glass. In this structure, the reflection is achieved either by total internal reflection or silvering of the outer cube surfaces. The second form uses mutually perpendicular flat mirrors bracketing an air space. These two types have similar optical properties. The larger the angle to the normal, the smaller is the fraction of light transmitted, until the angle when total internal reflection occurs. ...
A retroflector may consist of many very small versions of these structures incorporated in a thin sheet or in paint. In the case of paint containing glass beads, the paint glues the beads to the surface where retroreflection is required, and the beads protrude, their diameter being about twice the thickness of the paint.
A third, much less common way of producing a retroreflector is to use the nonlinear optical phenomenon of phase conjugation. This technique is used in advanced optical systems such as high-power lasers and optical transmission lines. Phase conjugate mirrors require a comparatively expensive and complex apparatus, as well as large quantities of power (as nonlinear optical processes can be efficient only at high enough intensities). However, phase conjugate mirrors have an inherently much greater accuracy in the direction of the retroreflection, which in passive elements is limited by the mechanical accuracy of the construction. Nonlinear optics is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the polarization P responds nonlinearly to the electric field E of the light. ...
Nonlinear optics is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the polarization P responds nonlinearly to the electric field E of the light. ...
Table of Opticks, 1728 Cyclopaedia Optics ( appearance or look in ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter. ...
Experiment with a laser (likely an argon type) (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: light amplification by stimulated emission of radiation. ...
Fiber Optic strands An optical fiber in American English or fibre in British English is a transparent thin fiber for transmitting light. ...
Applications
Retroreflectors on roads Retroreflection (sometimes called retroflection) is used on road surfaces, road signs, vehicles and clothing (large parts of the surface of special safety clothing, less on regular coats). When the headlights of a car illuminate a retroreflective surface, the reflected light is directed towards the car and its driver, and not wasted by going in all directions as with diffuse reflection. However, a pedestrian can see a retroreflective surface in the dark only if there is a light source directly between them and the reflector, e.g. a torch they carry, or directly behind them, e.g. a car approaching from behind. "Cat's eyes" are a particular type of retroreflector embedded in the road surface, used mostly in the UK and southern parts of the United States. Mountain road with hairpin turns in the French Alps For other uses, see Road (disambiguation). ...
See also: street sign theft External links http://homepages. ...
The Trikke is a Human Powered Vehicle (HPV) This article is about the means of transport. ...
// Girls wearing formal attire for dancing, an example of one of the many modern forms of clothing. ...
The reflection of a bridge in Indianapolis, Indianas Central Canal. ...
Look up Pedestrian in Wiktionary, the free dictionary. ...
A regular white cats eye of the kind invented by Shaw, marking the middle of the road. ...
Corner reflectors are better at sending the light back to the source over long distances, while spheres are better at sending the light to a receiver somewhat off-axis from the source, as when the light from headlights is reflected into the driver's eyes. A SAAB headlight with combination projector/reflector optics A headlight or headlamp is a lamp, usually attached to the front of a vehicle such as a car, with the purpose of illuminating the road ahead during periods of low visibility, such as night or precipitation. ...
// A human eye. ...
Retroreflectors can be embedded in the road (level with the road surface), or can be raised above the road surface. Raised reflectors are visible for a very long distance (typically 0.5-1 kilometer or more), while sunken reflectors are only visible at very close range due to the higher angle required to properly reflect the light. Raised reflectors are not generally used in areas that regularly experience snow during winter, as passing snowplows will tear them off the roadway. The stress on the roadway caused by cars running over any embedded objects also contributes to accelerated wear and pothole formation. The orange markers separate opposing traffic lanes. ...
A kilometer (Commonwealth spelling: kilometre), symbol: km is a unit of length in the metric system equal to 1,000 metres (from the Greek words χίλια (khilia) = thousand and μÎÏ„Ïο (metro) = count/measure). ...
A small sidewalk clearing plow in Ottawa, Canada A snowplow (or snow plow, US Engish; in UK English, snowplough or snow plough) is a vehicle, or a device intended for mounting on a vehicle, for removing snow and sometimes ice from outdoor surfaces, typically those serving transportation purposes. ...
The city of Los Angeles is famous for its large potholes. ...
Retroreflective road paint is thus very popular in Canada and increasingly the northern parts of the United States, as it is not affected by the passage of snowplows and does not affect the interior of the roadway. Where weather permits, embedded retroreflectors are preferred as they last much longer than road paint, which is weathered by the elements and ground away by the passage of vehicles.
- See also: Raised pavement marker
The orange markers separate opposing traffic lanes. ...
Retroreflectors used in motorcycle safety Conspicuity, or visibility as outlined by The Motorcycle Safety Foundation greatly increases a motorcyclist's chances of being seen by motorists at night. Placing retroreflective patches on clothing and helmets greatly increases the visibility of bikers and pedestrians to oncoming motorists.
Many materials appear to have some small degree of reflectivity, but retroreflective materials bounce the greatest amount of light back toward a light source. This makes them startlingly visible in dark conditions. Some patches claim to be reflective, but only retroreflective materials can be seen from more than a few feet away at night. Retroreflectivity of materials is measured in candle power. Official data says that white clothing performs up to 0.3 candle power. A vehicle license plate comes in at a level of 50. A conforming retro-reflective material has 500 candle power! There is a direct relationship between reflective index (candle power), and the distance from which it can be seen.
Retroreflectors on the Moon The Apollo 11, 14, and 15 missions left retro-reflectors on the Moon as part of the Lunar Laser Ranging Experiment. They are commonly considered to be one of the strongest pieces of evidence against a Moon landing hoax. Additionally the unmanned Soviet Lunokhod 1 and Lunokhod 2 rovers carried smaller arrays. Reflected signals were initially received from Lunokhod 1, but no return signals have been detected since 1971, at least in part due to some uncertainty in its location on the Moon. Lunokhod 2's array continues to return signals to Earth.[1] The Apollo 11 mission was the first mission to land on the Moon. ...
Apollo 14 was the eighth manned mission in the Apollo program and the third mission to land on the Moon. ...
Apollo 15 was the ninth manned mission in the Apollo program and the fourth mission to land on the Moon. ...
Apparent magnitude: up to -12. ...
The Lunar Laser Ranging Experiment from the Apollo 11 mission The ongoing Lunar Laser Ranging Experiment was first made possible by a lunar laser ranging retroreflector array planted on the Moon on July 21, 1969, by the crew of the Apollo 11. ...
It has been suggested that this article or section be merged with Independent evidence for Apollo Moon landings. ...
Lunokhod series Soviet Moon exploration robot vehicle A panorama shot from Lunokhod 1 A photo from Lunokhod 1 showing the Luna 17 lander The tracks of Lunokhod showing the little wheel in the center that was used for odometry. ...
Lunokhod series Soviet Moon exploration robot vehicle Lunokhod 2 was the second of two unmanned lunar rovers landed on the Moon by the Soviet Union as part of the Lunokhod program. ...
It is interesting to note [2] that even under good viewing conditions, only a single reflected photon is received every few seconds. This makes the job of filtering laser-generated photons from naturally-occurring photons challenging.
Retroreflectors in Earth orbit LAGEOS, or Laser Geodynamics Satellites, are a series of scientific research satellites designed to provide an orbiting laser ranging benchmark for geodynamical studies of the Earth. There are two LAGEOS spacecraft, LAGEOS-1 launched in 1976, and LAGEOS-2 launched in 1992. As of 2004, both LAGEOS spacecraft are still in service. The LAGEOS-1 satellite. ...
Retroreflectors and invisibility Retroreflective clothing, combined with a properly set up camera and projector, can be used to achieve the effect of partial invisibility when viewed from a single direction. An example of how an object could appear to be invisible through the use of mirrors Invisibility is the state of an object which cannot be seen. ...
More from BBC: [3] [4]
Howstuffworks has a good article on invisibility cloaks which are based on retroreflectors. See [5]
Retroreflectors and communications Modulated retroreflectors, in which the reflectance is changed over time by some means, are the subject of research and development for free-space optical communications networks. The basic concept with such systems is that a low-power remote system, such as a sensor mote, can receive an optical signal from a base station and reflect the modulated signal back to the base station. Since the base station supplies the optical power, this allows the remote system to communicate without excessive power consumption. Modulated retroreflectors also exist in the form of modulated phase-conjugate mirrors (PCMs). In the latter case, a "time-reversed" wave is generated by the PCM, with temporal encoding of the phase-conjugate wave (see, e.g., reference 6).
Cheap plastic corner retroreflectors are using as an aiming device in user-controlled technology optical datalink device Ronja. The aiming is done in night and the necessary retroreflector area depends on aiming distance and ambient lighting from street lamps. The optical receiver itself behaves as a weak retroreflector, because contains a large precisely focused lens and shiny object in the focal plane. This allows aiming without a retroreflector for short range. Ronja device installed on a balcony. ...
A lens. ...
Retroreflectors and surveying In surveying with a total station or robot, the instrument man or robot aims a laser beam at a corner cube retroreflector held by the rodman. The instrument measures the propagation time of the light and converts it to a distance. Surveyor at work with a leveling instrument. ...
Experiment with a laser (likely an argon type) (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: light amplification by stimulated emission of radiation. ...
Retroreflectivity used to detect digital cameras The sensor system of common (non-SLR) digital cameras is retroreflective. Researchers have used this property to demonstrate a system to prevent unauthorized photographs by detecting digital cameras and beaming a highly-focused beam of light into the lens.[6]
Other uses - Retroreflectors are used in movie screens. See [7]
References - Optics Letters, Vol. 4, pp. 190-192 (1979), "Retroreflective Arrays as Approximate Phase Conjugators," by H.H. Barrett and S.F. Jacobs.
- Optical Engineering, Vol. 21, pp. 281-283 (March/April 1982), "Experiments with Retrodirective Arrays," by Stephen F. Jacobs.
- Scientific American, December 1985, "Phase Conjugation," by Vladimir Shkunov and Boris Zel'dovich.
- Scientific American, January 1986, "Applications of Optical Phase Conjugation," by David M. Pepper.
- Scientific American, April 1986, "The Amateur Scientist" ('Wonders with the Retroreflector'), by Jearl Walker.
- Scientific American, October 1990, "The Photorefractive Effect," by David M. Pepper, Jack Feinberg, and Nicolai V. Kukhtarev.
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