|
Holography
Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other applications. In principle, it is possible to make a hologram for any type of wave. A hologram is made by superimposing a second wavefront (normally called the reference beam) on the wavefront of interest, thereby generating an interference pattern which is recorded on a physical medium. When only the second wavefront illuminates the interference pattern, it is diffracted to recreate the original wavefront. Holograms can also be computer-generated by modelling the two wavefronts and adding them together digitally. The resulting digital image is then printed onto a suitable mask or film and illuminated by a suitable source to reconstruct the wavefront of interest. Overview and history The Hungarian- British physicist Dennis Gabor (in Hungarian: ''Gábor Déne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holography
Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other applications. In principle, it is possible to make a hologram for any type of wave. A hologram is made by superimposing a second wavefront (normally called the reference beam) on the wavefront of interest, thereby generating an interference pattern which is recorded on a physical medium. When only the second wavefront illuminates the interference pattern, it is diffracted to recreate the original wavefront. Holograms can also be computer-generated by modelling the two wavefronts and adding them together digitally. The resulting digital image is then printed onto a suitable mask or film and illuminated by a suitable source to reconstruct the wavefront of interest. Overview and history The Hungarian- British physicist Dennis Gabor (in Hungarian: ''Gábor Déne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Holography
Electron holography is holography with electron waves. Dennis Gabor invented holography in 1948 when he tried to improve resolution in electron microscope. The first attempts to perform holography with electron waves were made by Haine and Mulvey in 1952; they recorded holograms of zinc oxide crystals with 60 keV electrons, demonstrating reconstructions with approximately 1 nm resolution. In 1955, G. Möllenstedt and H. Düker invented an electron biprism. thus enabling the recording of electron holograms in off-axis scheme. There are many different possible configurations for electron holography, with more than 20 documented in 1992 by Cowley. Usually, high spatial and temporal coherence (i.e. a low energy spread) of the electron beam are required to perform holographic measurements. High-energy electron holography in off-axis scheme Electron holography with high-energy electrons (80-200 keV) can be realized in a transmission electron microscope (TEM) in an off-axi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer-generated Holography
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. Alternatively, the holographic image can be brought to life by a holographic 3D display (a display which operates on the basis of interference of coherent light), bypassing the need of having to fabricate a "hardcopy" of the holographic interference pattern each time. Consequently, in recent times the term "computer-generated holography" is increasingly being used to denote the whole process chain of synthetically preparing holographic light wavefronts suitable for observation. Computer-generated holograms have the advantage that the objects which one wants to show do not have to possess any physical reality at all (completely synthetic hologram generation). On the other hand, if ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dennis Gabor
Dennis Gabor ( ; hu, Gábor Dénes, ; 5 June 1900 – 9 February 1979) was a Hungarian-British electrical engineer and physicist, most notable for inventing holography, for which he later received the 1971 Nobel Prize in Physics. He obtained British citizenship in 1934, and spent most of his life in England. Life and career Gabor was born as Günszberg Dénes, into a Jewish family in Budapest, Hungary. In 1918, his family converted to Lutheranism. Dennis was the first-born son of Günszberg Bernát and Jakobovits Adél. Despite having a religious background, religion played a minor role in his later life and he considered himself agnostic. In 1902, the family received permission to change their surname from Günszberg to Gábor. He served with the Hungarian artillery in northern Italy during World War I. He began his studies in engineering at the Technical University of Budapest in 1918, later in Germany, at the Charlottenburg Technical University in Berlin, now known as t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mieczysław Wolfke
Mieczysław Wolfke (29 May 1883 – 4 May 1947) was a Polish physicist, professor at the Warsaw University of Technology, the forerunner of holography and television. He discovered the method of solidification of helium as well as two types of liquid helium. He was a Masonic Grand Master of the National Grand Lodge of Poland from 1931–1934. He served as President of the Polish Physical Society between 1930–1934. Biography Mieczysław Władysław Wolfke was born on 29 May 1883 in Łask near Łódź. His father, Karol Juliusz Wolfke, was a road engineer. In 1892 Mieczysław and his parents moved to Częstochowa where his father became a district roadside engineer. At the age of 12, Wolfke wrote a dissertation about interplanetary travelling (especially to the Moon). It contained the theory of spaceships driven by the jet force. He also presented scientific hypotheses supported by mathematical models. In Częstochowa Mieczysław completed five years of the gymnasium for boy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffracted
Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wave. Italian scientist Francesco Maria Grimaldi coined the word ''diffraction'' and was the first to record accurate observations of the phenomenon in 1660. In classical physics, the diffraction phenomenon is described by the Huygens–Fresnel principle that treats each point in a propagating wavefront as a collection of individual spherical wavelets. The characteristic bending pattern is most pronounced when a wave from a coherent source (such as a laser) encounters a slit/aperture that is comparable in size to its wavelength, as shown in the inserted image. This is due to the addition, or interference, of different points on the wavefront (or, equivalently, each wavelet) that travel by paths of diff ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light which is ''coherent''. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar (light detection and ranging). Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum. Alternatively, temporal coherence can be used to produce ultrashort pulses of ligh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light Field
The light field is a vector function that describes the amount of light flowing in every direction through every point in space. The space of all possible '' light rays'' is given by the five-dimensional plenoptic function, and the magnitude of each ray is given by its radiance. Michael Faraday was the first to propose that light should be interpreted as a field, much like the magnetic fields on which he had been working. The phrase ''light field'' was coined by Andrey Gershun in a classic 1936 paper on the radiometric properties of light in three-dimensional space. Modern approaches to light field display explore co-designs of optical elements and compressive computation to achieve higher resolutions, increased contrast, wider fields of view, and other benefits. The term “radiance field” may also be used to refer to similar concepts. The term is used in modern research such as neural radiance fields. The plenoptic function For geometric optics—i.e., to incoherent ligh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
British Thomson-Houston
British Thomson-Houston (BTH) was a British engineering and heavy industrial company, based at Rugby, Warwickshire, England, and founded as a subsidiary of the General Electric Company (GE) of Schenectady, New York, United States. They were known primarily for their electrical systems and steam turbines. BTH was taken into British ownership and amalgamated with the similar Metropolitan-Vickers company in 1928 to form Associated Electrical Industries (AEI), but the two brand identities were maintained until 1960. The holding company, AEI, later merged with GEC. In the 1960s AEI's apprenticeships were highly thought-of, both by the apprentices themselves and by their future employers, because they gave the participants valuable experience in the design, production and overall industrial management of a very wide range of electrical products. Over a hundred of the apprentices - who came to Rugby from all over the UK, and a few from abroad - lodged in the nearby Apprentices' Host ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interference (wave Propagation)
In physics, interference is a phenomenon in which two waves combine by adding their displacement together at every single point in space and time, to form a resultant wave of greater, lower, or the same amplitude. Constructive and destructive interference result from the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, surface water waves, gravity waves, or matter waves. Etymology The word ''interference'' is derived from the Latin words ''inter'' which means "between" and ''fere'' which means "hit or strike", and was coined by Thomas Young in 1801. Mechanisms The principle of superposition of waves states that when two or more propagating waves of the same type are incident on the same point, the resultant amplitude at that point is equal to th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opacity (optics)
Opacity is the measure of impenetrability to electromagnetic radiation, electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a transmission medium, medium, such as a plasma (physics), plasma, dielectric, radiation shield, shielding material, glass, etc. An opaque object is neither Transparency (optics), transparent (allowing all light to pass through) nor translucent (allowing some light to pass through). When light strikes an interface between two substances, in general some may be reflected, some absorbed, some scattered, and the rest transmitted (also see refraction). Reflection can be diffuse reflection, diffuse, for example light reflecting off a white wall, or specular reflection, specular, for example light reflecting off a mirror. An opaque substance transmits no light, and therefore reflects, scatters, or absorbs all of it. Both mirrors and carbon black are opaque. Opacity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffuse Reflection
Diffuse reflection is the reflection (physics), reflection of light or other radiation, waves or particles from a surface such that a ray (optics), ray incident on the surface is scattering, scattered at many angles rather than at just one angle as in the case of specular reflection. An ''ideal'' diffuse reflecting surface is said to exhibit Lambertian reflection, meaning that there is equal luminance when viewed from all directions lying in the half-space (geometry), half-space adjacent to the surface. A surface built from a non-absorbing powder such as plaster, or from fibers such as paper, or from a polycrystalline material such as white marble, reflects light diffusely with great efficiency. Many common materials exhibit a mixture of specular and diffuse reflection. The visibility of objects, excluding light-emitting ones, is primarily caused by diffuse reflection of light: it is diffusely-scattered light that forms the image of the object in the observer's eye. Mechanism ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
