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5,268 terms
Photonics Dictionary
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Gauss lens
A telescope objective with excellent spherochromatic correction, consisting of a meniscus crown and a meniscus flint, both convex to the long conjugate.
Gauss points
->
cardinal points
Focal, nodal or principal points of a lens. If the respective distances of the object and image are measured from the cardinal points, all thin-lens equations are applicable to thick lenses.
Gaussian beam
A beam of light whose electrical field amplitude distribution is Gaussian. When such a beam is circular in cross section, the amplitude is E(r) = E(0) exp [-(r/w)2], where r is the distance from beam...
Gaussian beam optics
The area of optics that deals with the propagation of Gaussian laser beams in free space, or any general medium - i.e. lenses- under the paraxial (small divergence angle) approximations. Gaussian...
Gaussian optics
1. That branch of optics that illustrates the theory in which q is substituted for sin q in Snell's law. Effective results are achieved if the aperture and field angle are made very small. The...
Gaussian profile
An intensity distribution (intensity as a function of radial distance from the beam center) which is given by the Gaussian function: where: I0 is the intensity at the beam center r is the radial...
Gaussian pulse
A pulse that has the waveform of a Gaussian distribution.
GDD
group delay dispersion
GEDI lidar
The global ecosystem dynamics investigation (GEDI) lidar is a state-of-the-art spaceborne instrument designed to study Earth's forests and ecosystems in three dimensions. Developed by NASA, GEDI is...
gegenschein-zodiacal light photometer
A photometer used to measure sky brightness and polarization associated with zodiacal light, background starlight, F-region airglow and spacecraft corona.
Geiger counter
Also called Geiger-Müller counter. An instrument designed to detect and measure radioactivity through the use of a gas-filled metallic tube containing a needle electrode. Radiation traveling...
genlock
A device used to lock the internal synchronization generator of a television camera to an external source.
geometric concentration
->
area concentration
The ratio of aperture area over receiving area for a specific lens. Also called geometric concentration.
geometric extent
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etendue
A product of the area of a light beam (normal to its direction of propagation) and the solid angle that the beam includes; flux per unit radiance or luminance. Alternative terms: geometric extent,...
geometric image
The position and shape of the image of a point source, as predicted by geometric optics alone. The geometric image is to be differentiated from the diffraction image, which is determined from...
geometric metamerism
Metamerism that occurs when the geometry of illumination or viewing is changed.
geometric optics
A field of physics that deals with light as if it truly were composed of rays diverging in various directions from the source and abruptly bent by refraction or turned by reflection into paths...
geometric phase shifting
A technique used to create an achromatic phase shift based on the principle of geometric phase. The phase shift is experienced by a light beam as a result of a cyclic change in its state of...
Geometrical optics
The area of optics in which the propagation of light is described by geometrical lines (or rays) governed by Fermat's Principle. Geometrical optics is useful as long as the objects in which the light...
georectification
The superposition of satellite or aerial images with a map in order to process and remove distortion. Uses reference points from map to align and apply information.
GEOS
geodetic Earth orbiting satellite; geosynchronous Earth observation system
germanate glass
A type of glass used in near-infrared optical components, in which germanium is used as a cation instead of silicon.
germanium crystal
Germanium crystal refers to a crystalline form of the element germanium (Ge), which is a metalloid and semiconductor commonly used in various electronic and optical applications. Germanium crystals...
germicidal UV
Germicidal ultraviolet (GUV) refers to a specific range of UV radiation that has disinfectant properties capable of killing or inactivating microorganisms, including bacteria, viruses, and fungi. The...
getter
In vacuum deposition, a device that removes contaminants from the vacuum chamber.
ghost
1. A faint second image caused by reflection that is sometimes seen when observing through an optical instrument. 2. With respect to spectroscopy, a false image of a spectral line formed by...
GigE
GigE, short for gigabit Ethernet, refers to a standard for high-speed Ethernet communication, capable of transmitting data at rates of up to 1 gigabit per second (Gbps), or 1000 megabits per second...
gimbal mount
An optical mounting device that permits adjustment around two perpendicular and intersecting axes of rotation.
Gires-Tournois interferometer
An interferometer similar in construction to a Fabry-Perot interferometer but having a rear mirror with high reflectivity, allowing light to escape only at the partially reflective front mirror.
Glan spectrophotometer
A device similar to the ordinary spectrophotometer but containing particular modifications to provide for the comparison of two sources.
Glan-Foucault prism
A type of birefringent polarizing prism that transmits the extraordinary ray and removes the ordinary ray through total internal reflection. It consists of two calcite prisms with an air gap...
glass
A noncrystalline, inorganic mixture of various metallic oxides fused by heating with glassifiers such as silica, or boric or phosphoric oxides. Common window or bottle glass is a mixture of soda,...
glass barium
A type of glass containing barium oxide, which is added to increase the refractive index while maintaining a relatively low dispersion.
glass dosimeter
A device that detects and measures the quantity of exposure to nuclear radiation. It uses a special glass rod that fluoresces when placed under ultraviolet radiation after its exposure to nuclear...
glass film plates
An early form of photographic media consisting of glass plates coated with an emulsion.
glass laser
An optically pumped solid-state laser in which the active medium is a neodymium ion in a glass rod host. Abbreviated Nd:glass.
glass marking ink
Ink used for writing on glass, and also for blackening the edges of lenses to prevent reflection. In the latter case, the refractive index of the ink must closely match that of the glass.
glass spectrograph
A spectrograph having glass as its refracting component and used in cases where speed and high dispersion are not required. The glass material has a range of about 3700 to 8000 Å.
glass-melting furnace
A furnace used to heat glass materials. It may be a small laboratory-type furnace for small-scale experiments or large enough to hold gas-fired tanks for the commercial mass production of glass....
glitter
The specular reflection of individual parts of a surface.
global optimization
A controlled random search process, such as generalized simulated annealing, that has been incorporated into many optical design programs as a way of helping designers find the most suitable lens...
global radiation
The total radiation, both solar and diffuse sky, that is incident to a unit's horizontal surface.
globar
A light source made up of silicon carbide or carborundum. It is resistant to the negative temperature coefficient and mechanical distortion.
globulite
A crystal of microscopic size having no definite plane faces and having a globular shape. At the time the crystal is formed, the strong surface tension influences the formation of the plane faces.
gloss
Property of a surface which, because of directional reflection, is responsible for the degree to which reflected highlights or the images of objects may be seen as superimposed on the surface.
glow discharge
An electric discharge in a low-pressure gas having a low-current density and a space potential near the cathode that is much higher than the ionization potential of the gas but less than its sparking...
glow lamp
A lamp in which the ionization of the inert gas contained in it produces a glow in the space close to the negative electrode.
GMTF
geometric modulation transfer function
GOES
geostationary operational environmental satellite
Golay cell
A thermal radiation detector consisting of a small cell with a blackened plastic front face that bulges slightly when heat is received by it. The bulging tilts a small mirror, which, in turn, varies...
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Photonics Dictionary
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