of optical feedback
Optical feedback is the optical equivalent of acoustic feedback. Audio Feedback (also known as the Larsen effect after the Danish scientist Søren Larsen who first discovered its principles is a special kind of Feedback The feedback occurs when a loop exists between an optical input, for example, a videocamera and a television screen or monitor. Feedback is a circular causal Process whereby some proportion of a system's output is returned (fed back to the Input. A video camera is a Camera used for electronic Motion picture acquisition initially developed by the Television industry but now common in other applications Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic A video monitor also called a broadcast monitor, is a device similar to a Television, used to monitor the output of a video-generating device such as a media (A simple example of optical feedback is an image cast between mirrors. A mirror is an object with a surface that has good Specular reflection; that is it is smooth enough to form an Image. )
In this GIF movie, and the JPG still image examples (right), light from a candle is received by a videocamera, amplified and then sent by cable to a monitor projecting electron beams on the inside of the monitor screen. Generally an amplifier or simply amp, is any device that changes usually increases the amplitude of a signal. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The image on the monitor is then captured by the videocamera again, and fed back to the monitor in a continuous loop.
The original light source, in this case from the candle, can then be extinguished, while the feedback loop continues. For each loop the image is doubled and the image interferes with itself. In physics interference is the addition ( superposition) of two or more Waves that result in a new wave pattern The electronic loop moves with near light speed, but as the resulting image is projected onto the phosphor dots on the inside of the screen the speed is stopped for as long as allowed by the time the phosphor points glow, and thus creating a "queue" of illuminated dots on the screen. A phosphor is a substance that exhibits the phenomenon of Phosphorescence (sustained glowing after exposure to energized particles such as Electrons
The resulting images depend on different camera and monitor settings, such as light amplification, contrast, distance, angle and physical vibrations. Optical feedback can be combined with music, or other sound sources, to influence the image loop.
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In entertainment
Many artists have used optical feedback. An example is Queen's music video for Bohemian Rhapsody. Queen were an English rock band formed in 1970 in London by guitarist is a Song written by Freddie Mercury and originally recorded by the band Queen for their 1975 album ''A Night at the Opera''. The effect (in this simple case) can be compared to looking at oneself between two mirrors.
The opening titles sequence for the British sci-fi series Doctor Who employed this technique from 1963 to 1973 (black-and-white initially, redone from 1967, then redone again, in colour this time, from 1970). Doctor Who is a British science fiction television programme produced by the BBC. Black-and-white is a number of Monochrome forms in Visual arts.
In science
The optical feedback discussed so far—video feedback, created by a camera pointing at its own monitor—is actually just one particular example of optical feedback. Perhaps the most obvious example of optical feedback in science is the optical cavity found in almost every laser, which consists of two curved mirrors facing each other. An optical cavity or optical resonator is an arrangement of Mirrors that forms a Standing wave Cavity resonator for Light waves Optical A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. In the late 1990s it was found that so-called unstable cavity lasers in fact produce beams that are fractal shaped (Link to original article in Nature Vol. 402, 138 (11 November 1999)).
Optical feedback in science is often closely related to video feedback, so an understanding of video feedback is often very useful for other applications of optical feedback. Video feedback has, for example, been used to explain the fractal structure in laser beams.
Video feedback is also useful as an experimental-mathematics tool. Examples of its use include the creation of Fractal patterns using multiple monitors or multiple images created using mirrors. A fractal is generally "a rough or fragmented geometric shape that can be split into parts each of which is (at least approximately a reduced-size copy of the whole"
The page video feedback in science provides an overview.
Softology's Video Feedback page provides links and information about real and simulated video feedback.
In philosophy
Douglas Hofstadter uses a direct analogy to Optical feedback (Video feedback) in his book I Am a Strange Loop about the human mind and consciousness. Douglas Richard Hofstadter (born February 15 1945 in New York New York) is an American academic whose research focuses on consciousness thinking and creativity I Am a Strange Loop is a 2007 book by Douglas Hofstadter, examining in depth the concept of a Strange loop originally developed in his 1979
See also
- Video feedback
- Audio/Acoustic feedback
- Computer graphics
- Droste effect
- Feedback
- Interference
- Real-time computer graphics
- Self-reference
- Strange loop
- Video art
- Video
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