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Encyclopedia > Holograms

Holography (from the Greek, Όλος-holos whole + γραφή-graphe writing) is the science of producing holograms, an advanced form of photography that allows an image to be recorded in three dimensions. The technique of holography can also be used to optically store and retrieve information. Holograms are common in science-fiction, most notably Star Trek. Lens and mounting of a large format camera Photography is the process of making pictures by means of the action of light. ... Image of the Wikimedia Commons logo. ... Dimension (from Latin measured out) is, in essence, the number of degrees of freedom available for movement in a space. ... Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology upon society and persons as individuals. ... The Enterprise boldly going where no man had gone before. ...

Contents

Overview

Holography was invented in 1947 by Hungarian physicist Dennis Gabor (1900-1979), for which he received the Nobel Prize in physics in 1971. He recieved patent GB685286 on the invention. The discovery was an unexpected result of research into improving electron microscopes at the British Thomson-Houston Company in Rugby, England, but the field did not really advance until the invention of the laser in 1960. 1947 was a common year starting on Wednesday (link will take you to calendar). ... Dennis Gabor (Gábor Dénes) (5th June, 1900, Budapest - 9th February, 1979, London) was a Hungarian physicist who is most notable for inventing holography. ... 1900 is a common year starting on Monday. ... 1979 is a common year starting on Monday. ... List of Nobel Prize laureates in Physics from 1901 to the present day. ... 1971 is a common year starting on Friday (click for link to calendar). ... The electron microscope is a microscope that can magnify very small details with high resolving power due to the use of electrons rather than light to scatter off material, magnifying at levels up to 500,000 times. ... British Thomson-Houston (BTH) was a British Engineering company, founded in 1894 to manufacture in the UK, under licence, products patented by an American company (which was to become General Electric). ... Rugby is a market town in the county of Warwickshire in central England upon the River Avon. ... Royal motto: Dieu et mon droit (French: God and my right) Englands location within the UK Official language English de facto Capital London de facto Largest city London Area  - Total Ranked 1st UK 130,395 km² Population  - Total (2001)  - Density Ranked 1st UK 49,138,831 377/km² Religion... Laser (US Air Force) A laser (Light Amplification by Stimulated Emission of Radiation) is a device which uses a quantum mechanical effect, stimulated emission, to generate a coherent beam of light from a lasing medium of controlled purity, size, and shape. ... 1960 was a leap year starting on Friday (link will take you to calendar). ...


Several types of holograms can be made. The very first holograms were "transmission holograms", which were viewed by shining laser light through them. A later refinement, the "rainbow transmission" hologram allowed viewing by white light and is commonly seen today on credit cards as a security feature and on product packaging. These versions of the rainbow transmission holograms incorporate a reflective foil backing which provides the light from "behind" to reconstruct their imagery. Another kind of common hologram is the true "white-light reflection hologram" which is made in such a way that the image is reconstructed naturally using light on the same side of the hologram as the viewer. Missing image Credit cards A credit card system is a type of retail transaction settlement and credit system, named after the small plastic card issued to users of the system. ...


One of the most promising recent advances in the short history of holography has been the mass production of low-cost solid-state lasers - typically used by the millions in DVD recorders and other applications, but sometimes also useful for holography. These cheap, compact, solid state lasers can compete well with the large, expensive gas lasers previously required to make holograms, and are already helping to make holography much more accessible to low-budget researchers, artists, and dedicated hobbyists.


Technical description

The difference between holography and photography is best understood by considering what a Black & White (B&W) photograph actually is: it is a point-to-point recording of the intensity of light rays that make up an image. Each point on the photograph records just one thing, the intensity (i.e. the square of the amplitude of the electric field) of the light wave that illuminates that particular point. In the case of a colour photograph, slightly more information is recorded (in effect the image is recorded three times viewed through three different colour filters), which allows a limited reconstruction of the wavelength of the light, and thus its colour. In physics, intensity is a measure of the time-averaged energy flux. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye, or in a more general sense, any electromagnetic radiation in the range from infrared to ultraviolet. ... Amplitude is a nonnegative scalar measure of a waves magnitude of oscillation. ... In physics, an electric field or E-field is an effect produced by an electric charge that exerts a force on charged objects in its vicinity. ... For alternative meanings, see color (disambiguation). ... An optical filter is a device which selectively transmits light having certain properties (often, a particular range of wavelengths, i. ... The wavelength is the distance between repeating units of a wave pattern. ...


However, the light which makes up a real scene is not only specified by its amplitude and wavelength, but also by its phase. In a photograph, the phase of the light from the original scene is lost. In a hologram, both the amplitude and the phase of the light (usually at one particular wavelength) are recorded. When reconstructed, the resulting light field is identical to that which emanated from the original scene, giving a perfect three-dimensional image (albeit, in most cases, a monochromatic one, though colour holograms are possible). Waves with the same phase Waves with different phases The phase of a wave relates the position of a feature, typically a peak or a trough of the waveform, to that same feature in another part of the waveform (or, which amounts to the same, on a second waveform). ... Something which is monochromatic has a single color. ...


image:holography-record.png Diagram of the holographic recording process. ...


Hologram recording process


To produce a recording of the phase of the light wave at each point in an image, holography uses a reference beam which is combined with the light from the scene or object (the object beam). Optical interference between the reference beam and the object beam, due to the superposition of the light waves, produces a series of intensity fringes that can be recorded on standard photographic film. These fringes form a type of diffraction grating on the film. Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). ... The term superposition can have several meanings: Quantum superposition Law of superposition in geology and archaeology Superposition principle for vector fields Superposition Calculus is used for equational first-order reasoning This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... In optics, a diffraction grating is an array of fine, parallel, equally spaced grooves (rulings) on a reflecting or transparent substrate. ...


image:holography-reconstruct.png Diagram of the holographic reconstruction process. ...


Hologram reconstuction process


Once the film is processed, if illuminated once again with the reference beam, diffraction from the fringe pattern on the film reconstructs the original object beam in both intensity and phase. Because both the phase and intensity are reproduced, the image appears three-dimensional; the viewer can move their viewpoint and see the image rotate exactly as the original object would. Diffraction is the apparent bending and spreading of waves when they meet an obstruction. ...


Because of the need for interference between the reference and object beams, holography typically uses a laser to produce them. The light from the laser is split into two beams, one forming the reference beam, and one illuminating the object to form the object beam. A laser is used because the coherence of the beams allows interference to take place, although early holograms were made before the invention of the laser, and used other (much less convenient) coherent light sources such as mercury-arc lamps. Laser (US Air Force) A laser (Light Amplification by Stimulated Emission of Radiation) is a device which uses a quantum mechanical effect, stimulated emission, to generate a coherent beam of light from a lasing medium of controlled purity, size, and shape. ... Coherent waves. ... General Name, Symbol, Number Mercury, Hg, 80 Chemical series transition metals Group, Period, Block 12 (IIB), 6, d Density, Hardness liquid 13. ...


The coherence length of the beam determines the maximum depth the image can have. A laser will typically have a coherence length of several meters, ample for a deep hologram. Small pen laser pointers tend to have a smaller coherence length and were considered too small to do holography. That has been shown to be incorrect, and people have successfully made small holograms with laser pens. Large analogue holograms cannot be made with laser pens due to their lower power (typically 1mW to 5mW). Digital holography does not suffer from this problem. Coherent waves. ...


Other applications of holograms include metrology and optical computing. Measurement is the determination of the size or magnitude of something. ... An Optical Computer is a computer that performs its computation with photons as opposed to the more traditional electron-based computation. ...


Holography in art

Salvador Dalí claims to have been the first to employ holography artistically. He was certainly the first and most notorious Catalan surrealist to do so, but the 1972 New York exhibit of Dali holograms had been preceded by "the first holographic art exhibition [which] was held at the Cranbrook Academy of Art in Michigan in 1968. The second took place at the Finch College gallery in New York in 1970 and attracted national media attention." (source: http://www.holophile.com/history.htm ). A vastly entertaining account of a 1973 Dali holography project (with Alice Cooper as subject) can be found here: http://www.alicecoopertrivia.pwp.blueyonder.co.uk/people/p-dali.php Salvador Dalí as photographed in 1934 by Carl Van Vechten Salvador Domenec Felip Jacint Dalí Domenech ( May 11, 1904 – January 23, 1989) was an important Catalan- Spanish painter, best known for his surrealist works. ...


Holographic data storage

See the main article at holographic memory. Holographic memory is a technique that can store information at high density inside crystals (à la HAL 9000) or photopolymers. ...


Holography can be applied to a variety of uses other than recording images. Holographic data storage is a technique that can store information at high density inside crystals (à la HAL 9000) or photopolymers. As current storage techniques such as DVD reach the upper limit of possible data density (due to the diffraction limited size of the writing beams), holographic storage has the potential to become the next generation of storage media. The advantage of this type of data storage is that the volume of the recording media is used instead of just the surface. HAL 9000 (Heuristically programmed ALgorithmic computer) is a fictional character in the Space Odyssey series, the first being the novel and film 2001 A Space Odyssey, written by Arthur C Clarke. ... DVD is an optical disc storage media format that can be used for storing data, including movies with high video and sound quality. ... Diffraction is the apparent bending and spreading of waves when they meet an obstruction. ...


Using currently available SLM's can produce about 1000 different images a second at 1024 X 1024 bit resolution. With the right type of media (probably polymers rather than something like LiNbO3), this would result in about 1 Gigabit per second writing speed. Read speeds can surpass this and experts believe 1 Terabit per second readout is possible. A spatial light modulator (SLM) is an object that imposes some form of spatially-varying modulation on a beam of light. ...


In 2005, the company Optware has produced a 120 mm disc that uses holographic surface to store data to a possible 1TB (terabyte). See Holographic Versatile Disc, for more information. A terabyte (derived from the SI prefix tera-) is a unit of information or computer storage equal to one trillion (one long scale billion) bytes. ... A HVD disc Holographic Versatile Disc structure 1. ...


External links


  Results from FactBites:
 
Holography - Wikipedia, the free encyclopedia (2265 words)
The first holograms which recorded 3D objects were made by Emmett Leith and Juris Upatnieks in Michigan, USA in 1963 and by Yuri Denisyuk in the Soviet Union.
Another kind of common hologram is the true "white-light reflection hologram" which is made in such a way that the image is reconstructed naturally using light on the same side of the hologram as the viewer.
In a hologram, both the amplitude and the phase of the light (usually at one particular wavelength) are recorded.
The Universe as a Hologram (3337 words)
A hologram is a three- dimensional photograph made with the aid of a laser.
If a hologram of a rose is cut in half and then illuminated by a laser, each half will still be found to contain the entire image of the rose.
Just as a hologram functions as a sort of lens, a translating device able to convert an apparently meaningless blur of frequencies into a coherent image, Pribram believes the brain also comprises a lens and uses holographic principles to mathematically convert the frequencies it receives through the senses into the inner world of our perceptions.
  More results at FactBites »

 
 

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