Invisibility

By using two parabolic cylindric mirrors and one plane mirror, the image of the background is directed around an object, making the object itself invisible - at least from two sides.

Invisibility is the state of an object that cannot be seen. An object in this state is said to be invisible (literally, "not visible"). The phenomenon is studied by physics and perceptual psychology.

Since objects can be seen by light from a source reflecting off their surfaces and hitting the viewer's eyes, the most natural form of invisibility (whether real or fictional) is an object that neither reflects nor absorbs light (that is, it allows light to pass through it). This is known as transparency, and is seen in many naturally occurring materials (although no naturally occurring material is 100% transparent).

Invisibility perception depends on several optical and visual factors.[1] For example, invisibility depends on the eyes of the observer and/or the instruments used. Thus an object can be classified as "invisible" to a person, animal, instrument, etc. In research on sensorial perception it has been shown that invisibility is perceived in cycles.[2]

Invisibility is often considered to be the supreme form of camouflage, as it does not reveal to the viewer any kind of vital signs, visual effects, or any frequencies of the electromagnetic spectrum detectable to the human eye, instead making use of radio, infrared or ultraviolet wavelengths.

In illusion optics, invisibility is a special case of illusion effects: the illusion of free space.

The term is often used in fantasy and science fiction, where objects cannot be seen by means of magic or hypothetical technology.

  1. ^ Moreno, Ivan; Jauregui-Sánchez, Y.; Avendaño-Alejo, Maximino (2014). "Invisibility assessment: a visual perception approach" (PDF). Journal of the Optical Society of America A. 31 (10): 2244–2248. Bibcode:2014JOSAA..31.2244M. doi:10.1364/josaa.31.002244. PMID 25401251. Archived from the original (PDF) on 2017-08-08. Retrieved 2016-01-24.
  2. ^ Craig, Eugene A.; Lichtenstein, M. (1953). "Visibility-Invisibility Cycles as a Function of Stimulus-Orientation". The American Journal of Psychology. 66 (4): 554–563. doi:10.2307/1418951. JSTOR 1418951. PMID 13124563.

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