547 terms
Photonics Dictionary: A
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ASangular sensitivity
ASATantisatellite
ASCIIAmerican Standard Code for Information Interchange
ASDSRSautomatic spectrum display and signal recognition system
ASEamplified spontaneous emission
ASFIRactive swept frequency interferometer radar
ASIAmerican Standards Institute
ASICapplication-specific integrated circuit
ASIIAmerican Science Information Institute
ASISAmerican Society for Information Science
ASKamplitude shift keying
ASKAautomatic system for kinematic analysis
ASLMSAmerican Society for Lasers in Medicine and Surgery
ASMampere second meter
ASNTAmerican Society for Nondestructive Testing
aspect of imageThe particular orientation of the image, such as normal, canted, inverted or reverted.
aspect ratioWith respect to pictorial displays, the ratio of the width to the height. The television standard in the US is 4:3. High-definition or wide-screen television will have a ratio of 16:9.
asphericNot spherical; an optical element having one or more surfaces that are not spherical. The spherical surface of a lens may be slightly altered so as to reduce spherical aberration. Aspheric surfaces...
aspheric lens systemAn optical system having one or more lens or mirror components that have nonspherical surfaces. These surfaces, whether reflecting or refracting, serve to advance or retard the incident wavefront,...
aspheric lensAn aspheric lens is a type of lens whose surface profiles deviate from the traditional spherical shape. Unlike spherical lenses, which have a constant curvature across their surfaces, aspheric lenses...
aspheric mirrorAn aspheric mirror is an optical mirror surface that deviates from the shape of a perfect sphere, having a non-spherical surface profile. Unlike traditional spherical mirrors, which have a curved...
aspherizingThe modification of the spherical surfaces in an optical system to correct for spherical aberration.
assist gasA gas, such as oxygen, that improves the speed and efficiency of a laser cutter or welder when applied to the work surface, or an inert gas, such as argon, that helps to clean or shield the work...
astigmatic differenceIn an optical system having astigmatism, the distance between the tangential and sagittal image planes.
astigmatic spectral lineIn an astigmatic grating, the image of the entrance slit located at the primary focus.
astigmatismA lens aberration that results in the tangential and sagittal image planes being separated axially.
astigmatizerA cylindrical lens that may be rotated to distort a bundle of light originating at a point source, to form a line image.
ASTMAmerican Society for Testing and Materials
Aston dark spaceIn the discharge of a vacuum tube, the narrow, nonluminous region that sometimes may be found between the cathode and its glow.
astrometryThe analysis and measurement of celestial bodies, their motions and positions.
astronomical cameraA camera designed to record astronomical objects (e.g., stars, planets, nebulae, galaxies) and their spectra.
astronomical mirrorAn astronomical mirror, also known as a telescope mirror or primary mirror, is a key component of a reflecting telescope. It serves as the primary optical element responsible for gathering and...
astronomical observatoryA facility designed for the observation and recording of astronomical phenomena.
astronomical photographyThe use of photographs to record astronomical objects and phenomena for purposes of physical observation and measurement of motion, radiation and spectra.
astronomical scintillationAny irregular motion, variation in intensity or change in color that arises because of atmospheric turbulence during the observation of an astronomical phenomenon or object.
astronomical spectrographAn instrument that photographs the spectra of an extraterrestrial object.
astronomical spectroscopyThe process of using a spectrograph with a telescope to acquire information on an astronomical object's speed and physical characteristics.
astronomical telescopeAn astronomical telescope is a type of optical instrument designed to gather and magnify light from distant celestial objects for observation and analysis. It typically consists of two main optical...
astronomical unitThe unit generally used to express distances within the solar system, and sometimes to measure interstellar distances. Technically, one astronomical unit is the mean distance between the Earth and...
astronomyThe scientific observation of celestial radiation that has reached the vicinity of Earth, and the interpretation of these observations to determine the characteristics of the extraterrestrial bodies...
AstrositalA glass-ceramic material developed in Russia. Astrosital resembles Zerodur in terms of its ultralow thermal expansion. Other spellings include Astro-Sital and Astro-Sitall.
asymasymmetric
asymptotic spectral reflectanceThe unchanging nature of spectral reflectance as vegetational density increases to the point where additional increases in leaf area index or biomass do not cause a change in the spectral reflectance.
asynchronous transfer modeA method of data multiplexing that can provide large, instantaneous bandwidths for busy traffic while permitting slow traffic to use that bandwidth between bursts. Very short, fixed-length packets or...
asynchronous transmissionA mode of data transmission whereby each bit of information is generated separately, with some stop/start code to indicate the interval between bits.
ATatomic time
ATARSadvanced tactical air reconnaissance system
ATDMAsynchronous Time Division Multiplexing
ATEautomatic test and evaluation
ATLISautomatic tracking laser illumination system
Photonics DictionaryA