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5,268 terms
Photonics Dictionary
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gold colloid aggregates
Gold colloid aggregates refer to clusters or assemblies of gold nanoparticles suspended in a liquid medium. These aggregates are formed when individual gold nanoparticles come together due to various...
gold vapor laser
->
metal vapor laser
Devices in which the lasing medium is a vapor of metal atoms or ions, sometimes mixed with another gas. Metal vapor lasers use a variety of metal types to generate a variety of laser lines for...
Golgi Staining Technique
The Golgi staining technique (also called the black reaction) makes it possible to look at the nervous system by rendering neurons visible under light microscopy. After a long process involving...
goniophotometer
A device used to measure directional reflectance, with light collection restricted to a narrow range of angles of which the central angle varies.
goniophotometric curve
The graphed curve illustrating the directional reflectance of a sample for different angles of collection.
GORID
ground optical recorder for intercept determination
GOSIP
government open systems interconnection profile
GPC
graphics performance characterization
GPS
global positioning system
graded reflectivity mirror
A mirror whose percent reflectance varies as a function of position on the mirror surface.
gradient
In image processing and machine vision, the rate of change of pixel intensity.
gradient edge enhancement
Edge enhancement with a directional characteristic.
gradient vector
In an image, the orientation and magnitude of the rate of change in intensity at any point.
gradient-index profile
The term gradient-index profile refers to a specific type of refractive index distribution within an optical material. In optics, the refractive index of a material describes how much the speed of...
gram negative
Gram-negative bacteria are a group of bacteria that possess a cell envelope composed of a thin layer of peptidoglycan surrounded by an outer membrane. This outer membrane contains lipopolysaccharides...
gram positive
Gram-positive bacteria are a group of bacteria that have a thick cell wall composed primarily of a substance called peptidoglycan. This thick peptidoglycan layer retains a stain called crystal violet...
graphecon
An electron tube having two electron guns, one on each side of the storage medium, to encode the information onto the medium, and to read and simultaneously erase the electrostatic encoding.
graphene
Graphene is a two-dimensional allotrope of carbon consisting of a single layer of carbon atoms arranged in a hexagonal lattice pattern. It is the basic building block of other carbon-based materials...
graser
An acronym of gamma ray amplification by stimulated emission of radiation. It is a gamma ray laser that operates between energy levels established by metastable isomeric transitions in the nucleus.
graser
gamma ray amplification by stimulated emission of radiation
Grashof number
Formula used in convection study to express the ratio of buoyant force to viscous force.
grating
A framework or latticework having an even arrangement of rods, or any other long narrow objects with interstices between them, used to disperse light or other radiation by interference between wave...
grating beamsplitter
A grating beamsplitter is an optical device that utilizes the principles of diffraction to split a beam of light into multiple beams, often redirecting them at specific angles. It is based on the...
grating monochromator
An optical instrument used to isolate a narrow bandwidth of optical radiation using a diffraction grating as the dispersive element. See also monochromator.
grating prism
A specific, right-angle prism having a transmission grating replicated on its hypotenuse face and used in applications requiring a system that can produce in-line viewing for one wavelength.
grating spectrograph
->
spectrograph
An optical instrument for forming the spectrum of a light source and recording it on a film. The dispersing medium may be a prism or a diffraction grating. A concave grating requires no other means...
grating spectroscope
A spectroscope having a diffraction grating for the resolution of light of various wavelengths.
grating substrate
The substrate upon which a diffraction grating will be ruled. It must be dimensionally stable, and the surface must be polished to an accurate flat or spherical form as required by the grating. The...
gravimeter
An instrument capable of precise measurements of the Earth's gravity. This permits the detection of small changes in local height that indicate changes in the Earth's crust and subsurface density.
gravitational imaging
A process used to detect minute gravitational fields and to display images from objects by means of radiated gravitational imagery.
gravitational lens
The effect of a powerful gravitational field on light traveling through the field. This effect is detectable in astronomical observations when light from a distant source passes a massive object...
gravitational waves
Postulated by Einstein in his theory of relativity. They are waves traveling at the speed of light and exerting force on matter in their path. They are produced by changes in the distribution of...
gray filter
->
neutral density filter
A light filter that equally decreases the intensity of all wavelengths of light without altering the relative spectral distribution of the energy.
gray levels
In image processing, machine vision and television, discrete brightness values quantized for a group of pixels. They can range from white, through various shades of gray, to black.
gray scales
Transparencies that represent progressive steps in the amount of transmitted radiation for administering predetermined amounts of radiation to a radiation-sensitive substance. The steps are...
gray
1. A measure of absorbed dose, equal to the energy imparted by ionizing radiation to a mass of matter corresponding to 1 J per kilogram. 2. A term used to denote an incompletely polished surface that...
gray-scale modification
Image enhancement operations that involve altering gray-scale values. For instance, brightness sliding involves adding or subtracting an identical brightness value to or from each pixel in an image;...
grazing emergence
A condition in which an emergent ray is perpendicular to the normal of the emergent surface of a medium.
green block
A porous ceramic substance that is ground to a given optical form and on which a polished plate of glass is sagged by heat application. It is capable of transmitting in a partial vacuum. The glass...
Gregorian telescope
A telescope with an ellipsoidal secondary concave mirror that reflects rays from a parabolic primary mirror through an opening in the center of the primary, where the image is viewed with an eyepiece.
GRIN lens
A GRIN (gradient index) lens is a type of optical lens that utilizes a gradient in refractive index across its volume rather than having a uniform refractive index like conventional lenses. This...
grinding and polishing machinery
Machinery used to grind and finish a component, such as a lens or prism, to a desired precision. Usually such machines carry a cup-shaped or flat tool (lap) into close contact with the part. An...
Grittington test
A method of determining the abrasion resistance of very hard materials by passing a weighted wiper blade across them in a sand-water slurry for a specified number of times.
ground glass
A plate of glass in which a face has been frosted by grinding or etching. It diffuses light by scattering in directions close to the incoming beam, but the light falls off rapidly at larger angles...
ground state
Also known as ground level. The lowest energy level of an atom or atomic system. A material in the ground state is not capable of emitting optical radiation. All other states are called excited...
ground truth
A term variously applied to remote sensing techniques that essentially refers to all parametric conditions that influence the sensor system; includes the quantitative reality that the sensor sees and...
grown-junction photocell
A photodiode that has been designed so that the bar of semiconductor material has a PN junction perpendicular to its length and an ohmic contact at each of its ends.
Gudden-Pohl effect
The light flash that occurs when an electrical field is applied to a phosphor already excited by ultraviolet radiation.
guided mode
In an optical waveguide, a mode whose field decays monotonically in the transverse direction everywhere external to the core and which does not lose power to radiation. Also called bound mode.
guided wave
A wave in which energy is focused near a boundary separating materials having different properties. Propagation of the wave is in a direction parallel to the boundary.
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Photonics Dictionary
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