528 terms
Photonics Dictionary: A
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apogeeThe point on an elliptical orbit about the Earth that is the farthest distance from the Earth.
APOMAAmerican Precision Optics Manufacturers Association
apostilbA unit of luminance equal to 1/p candela per square meter.
apparent contrastThe perceived brightness difference between light and dark areas on a target.
apparent fieldThe angular subtense of the field of view in the image space of a telescope, as differentiated from that in the object space (the true field).
apparent luminanceThe perceived brightness of an object being viewed at some distance, especially through an optical instrument.
apparent movementThe visual perception of motion when fixed stimuli are exposed in rapid temporal and spatial succession.
apparent visual angleThe angle subtended by an object, determined by the size of the object and its distance from the viewer.
APSactive pixel sensor; active pixel system; Advanced Photon Source; American Physical Society; atom probe spectroscopy; autocorrelated photon spectroscopy
APTautomatic picture transmission
aptamerAn aptamer is a short, single-stranded DNA or RNA molecule that can bind to a specific target molecule with high affinity and specificity. Aptamers are often referred to as chemical antibodies due to...
aqueous humorThe transparent fluid that fills the portion of the eye between the cornea and the eye lens (the anterior chamber).
ARAbbe refractometer; acoustic radiometer; acoustic resonance; active region; alpha ray; amplitude ratio; antireflective; aperture ratio; applied research; argon; aspect ratio; atomic reactor; augmented reality
Arago spotA bright spot or point, due to Fresnel diffraction, that appears at the center of the shadow of a circular object in light originating from a point source. Also referred to as a Fresnel spot or...
arc dischargeThe electric arc that is a particular discharge between two electrodes in a gas or vapor which is characterized by high cathode densities and a low voltage drop.
arc flashAn arc flash is a sudden release of electrical energy due to an electric arc — a continuous, high-current discharge of electricity between conductors or from a conductor to ground. Arc flashes...
arc light sourceIn present usage, especially for spectroscopic identification, an arc between electrodes that serves as a radiation source. Gas tubes that contain mercury vapor and mixtures of helium, neon and argon...
arc spectrumThe spectrum of the light produced by vaporizing an element in an electric arc.
arcuate displacementDisplacement in a direction perpendicular to that of the intended displacement, as in a translation stage with simple flexures that experiences vertical displacement during horizontal motion; it is...
AREactivated reactive evaporation
area concentrationThe ratio of aperture area over receiving area for a specific lens. Also called geometric concentration.
area image sensor -> mosaic detector arrayA group of photosensors arranged in a grid-like pattern covering the entire field of view, enabling them to record it all at once (as a camera records an image on film) rather than by scanning parts...
area scanArea scan, in the context of imaging and cameras, refers to a method of capturing an entire two-dimensional image in a single snapshot or exposure. Unlike line scan, which captures images one line at...
argon-ion lasergas laser using ionized argon as the active medium and applying electronic excitation in order to produce the laser light
ARLacceptable reliability level
ARMantiradiation missile
armorA protective jacket added to an optical fiber to facilitate use in harsh environments. Armor usually consists of steel or aluminum and is placed between the fiber and its outer jacket.
array processorIn image processing, a specially designed programmable computer peripheral that attaches to the host system for the purpose of more rapid arithmetical calculations than the latter can supply. The...
Arrhenius plotThe plot that expresses a reaction rate vs. the reciprocal of absolute temperature. Often used to describe the thermal characteristics of laser applications such as ablation or annealing.
ARROWantiresonant reflecting optical waveguide
arsenic trisulfideA dark red opaque material that is transparent to the infrared beyond 1 µm.
artificial intelligenceThe ability of a machine to perform certain complex functions normally associated with human intelligence, such as judgment, pattern recognition, understanding, learning, planning, and problem...
artificial pupiliris or adjustable radially symmetric opening used for allowing the passage of useful light
artificial radioactivityRadioactivity formed by the bombardment of stable elements by either neutrons or high-energy, charged particles under regulated conditions.
artificial starA point source of light used for the test and evaluation of image quality. May be a backlit pinhole in an otherwise opaque sheet placed at an appropriately large distance from the lens being tested.
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
Photonics DictionaryA