Holography is a technique that enables a wavefront to be recorded and later reconstructed. It is best known as a method of generating real three-dimensional images, but also has a wide range of other applications. In principle, it is possible to make a hologram for any type of wave.
A laser lighting display or laser light show involves the use of laser light to entertain an audience. A laser light show may consist only of projected laser beams set to music, or may accompany another form of entertainment, typically musical performances.
In computing, an optical disc drive is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only read from certain discs, but recent drives can both read and record, also called burners or writers. Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives.
A magneto-optical drive is a kind of optical disc drive capable of writing and rewriting data upon a magneto-optical disc. Both 130 mm (5.25 in) and 90 mm (3.5 in) form factors exist. In 1983, just a year after the introduction of the compact disc, Kees Schouhamer Immink and Joseph Braat presented the first experiments with erasable magneto-optical compact discs during the 73rd AES Convention in Eindhoven. The technology was introduced commercially in 1985. Although optical, they normally appear as hard disk drives to an operating system and can be formatted with any file system. Magneto-optical drives were common in some countries, such as Japan, but have fallen into disuse.
A signal beam or object beam is one of at least two laser beams used to write holograms. The signal beam is the beam that carries the information to be stored in the hologram. In the case of a holographic picture, this beam is reflected off the object being recorded, into the media. In the case of holographic data storage, the beam has some kind information encoded into it.
The photorefractive effect is a nonlinear optical effect seen in certain crystals and other materials that respond to light by altering their refractive index. The effect can be used to store temporary, erasable holograms and is useful for holographic data storage. It can also be used to create a phase-conjugate mirror or an optical spatial soliton.
Holographic Data Storage System (HDSS) program was a US Federal government-funded consortium on holographic data storage by Teledyne Technologies, IBM and Stanford University, created in 1995. Work on the program began in 1994 and was funded by DARPA.
Holographic data storage is a potential technology in the area of high-capacity data storage. While magnetic and optical data storage devices rely on individual bits being stored as distinct magnetic or optical changes on the surface of the recording medium, holographic data storage records information throughout the volume of the medium and is capable of recording multiple images in the same area utilizing light at different angles.
The rainbow or Benton hologram is a type of hologram invented in 1968 by Dr. Stephen A. Benton at Polaroid Corporation. Rainbow holograms are designed to be viewed under white light illumination, rather than laser light which was required before this. The rainbow holography recording process uses a horizontal slit to eliminate vertical parallax in the output image, greatly reducing spectral blur while preserving three-dimensionality for most observers. A viewer moving up or down in front of a rainbow hologram sees changing spectral colors rather than different vertical perspectives. Because perspective effects are reproduced along one axis only, the subject will appear variously stretched or squashed when the hologram is not viewed at an optimum distance; this distortion may go unnoticed when there is not much depth, but can be severe when the distance of the subject from the plane of the hologram is very substantial. Stereopsis and horizontal motion parallax, two relatively powerful cues to depth, are preserved.
Ultra Density Optical (UDO) is an optical disc format designed for high-density storage of high-definition video and data. The format was introduced by Sony to replace the Magneto-optical disc format.
For holographic data storage, holographic associative memory (HAM) is an information storage and retrieval system based on the principles of holography. Holograms are made by using two beams of light, called a "reference beam" and an "object beam". They produce a pattern on the film that contains them both. Afterwards, by reproducing the reference beam, the hologram recreates a visual image of the original object. In theory, one could use the object beam to do the same thing: reproduce the original reference beam. In HAM, the pieces of information act like the two beams. Each can be used to retrieve the other from the pattern. It can be thought of as an artificial neural network which mimics the way the brain uses information. The information is presented in abstract form by a complex vector which may be expressed directly by a waveform possessing frequency and magnitude. This waveform is analogous to electrochemical impulses believed to transmit information between biological neuron cells.
Holographic interferometry (HI) is a technique which enables static and dynamic displacements of objects with optically rough surfaces to be measured to optical interferometric precision. These measurements can be applied to stress, strain and vibration analysis, as well as to non-destructive testing and radiation dosimetry. It can also be used to detect optical path length variations in transparent media, which enables, for example, fluid flow to be visualised and analyzed. It can also be used to generate contours representing the form of the surface.
Digital holography refers to the acquisition and processing of holograms with a digital sensor array, typically a CCD camera or a similar device. Image rendering, or reconstruction of object data is performed numerically from digitized interferograms. Digital holography offers a means of measuring optical phase data and typically delivers three-dimensional surface or optical thickness images. Several recording and processing schemes have been developed to assess optical wave characteristics such as amplitude, phase, and polarization state, which make digital holography a very powerful method for metrology applications .
Computer-generated holography (CGH) is the method of digitally generating holographic interference patterns. A holographic image can be generated e.g., by digitally computing a holographic interference pattern and printing it onto a mask or film for subsequent illumination by suitable coherent light source.
3D optical data storage is any form of optical data storage in which information can be recorded or read with three-dimensional resolution.
Volume holograms are holograms where the thickness of the recording material is much larger than the light wavelength used for recording. In this case diffraction of light from the hologram is possible only as Bragg diffraction, i.e., the light has to have the right wavelength (color) and the wave must have the right shape. Volume holograms are also called thick holograms or Bragg holograms.
A holographic display is a type of 3D display that utilizes light diffraction to display a three-dimensional image to the viewer. Holographic displays are distinguished from other forms of 3D displays in that they do not require the viewer to wear any special glasses or use external equipment to be able to see the image, and do not cause the vergence-accommodation conflict.
Security holograms are labels with a hologram printed onto it for sale security reasons.
A CD-ROM is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both computer data and audio with the latter capable of being played on a CD player, while data is only usable on a computer.
Optical holography is a technique which enables an optical wavefront to be recorded and later re-constructed. Holography is best known as a method of generating three-dimensional images but it also has a wide range of other applications.
