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Photonics Dictionary

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antiferromagnetism
The elimination of magnetic moments and decrease in magnetic susceptibility with a decrease in temperature due to the equal power of atomic magnets.
antifog coating
A coating that is capable of stopping the condensation of moisture on an optical surface.
antigen
An antigen is any substance that is capable of triggering an immune response in an organism. Antigens are typically proteins or large polysaccharides, although other types of molecules can also act...
antiguide
A waveguide that has a core with a lower refractive index than the refractive index of the cladding. This structure can limit the power of the transmitted beam by removing unwanted radiation, for...
antihalation backing
Light-absorbing material that is applied to the back support of any bright image under inspection to prevent the formation of a secondary image.
antireflection coating
An antireflection coating (AR coating) is a thin film or coating applied to optical surfaces, such as lenses or windows, to minimize unwanted reflections and increase the transmission of light...
antiresonance
Literally the opposite of resonance, antiresonance occurs when any variation in excitation frequency results in an increased response.
antisolar point
The point to which the extension of the straight line, reaching from the sun to the observer's eye after penetrating the atmosphere of the Earth, is projected.
AOBD
acousto-optic beam deflector
AOD
acousto-optic deflector
AOI
area of interest; automatic optical inspection
AOM
acousto-optic modulator
AOTF
acousto-optic tunable filter
APA
all points addressable
APC
automatic power control; angle polished connector
APCVD
atmospheric pressure chemical vapor deposition
APD
avalanche photodiode
APD detector
An APD detector, or avalanche photodiode detector, is a type of photodetector used to detect light or optical signals by converting incoming photons into electrical current. It operates based on the...
apertometer
An instrument designed to measure the numerical aperture of an objective.
aperture
An opening or hole through which radiation or matter may pass.
aperture card
A combination 80-column computer card containing a 35-mm microfilm frame. Reference data can be punched onto the card to facilitate retrieval of it on film.
aperture diaphragm
The second adjustable iris diaphragm in an optical system. In the common microscope condenser system, it usually is located beneath the substage condenser on a transmitted light microscope. When the...
aperture distortion
A loss of resolution or detail in a television signal caused by the size of the electron scanning beam.
aperture illumination
The amplitude, polarization and phase contained in the field distribution over the aperture.
aperture imaging
The formation of an image by a pinhole aperture that transmits radiation, such as gamma radiation.
aperture mask
Also known as a shadow mask, a perforated plate placed between the focusing and accelerating electrodes, and the tricolor phosphor screen in a color-television tube.
aperture ratio
The ratio of the lens aperture to its focal length (1/f/#).
aperture stop
A physical constraint, often a lens retainer, that limits the diameter of the axial light bundle allowed to pass through a lens.
aphelion
The point of a planet or comet's orbit that is farthest from the sun.
API
application programming interface
APL
average picture level
aplanat
Also known as aplanatic lens. A lens corrected for spherical aberration and coma.
aplanatic lens system
A system that satisfies the Abbe sine condition, and is free from spherical aberration and coma.
aplanatic points
Aplanatic points refer to specific points in an optical system where certain aberrations, such as spherical aberration or coma, are minimized or eliminated. In an optical system, aberrations are...
aplanatic surface
An aplanatic surface is an optical surface that is specifically designed or shaped to minimize spherical aberration and coma. Spherical aberration is an optical aberration that occurs when light rays...
apochromat
An apochromat, often referred to as an apochromatic lens or apochromatic objective, is a type of optical system designed to minimize chromatic aberration. Chromatic aberration occurs when different...
apochromatic system
An optical system that is corrected chromatically for three colors simultaneously.
apodization
The use of a variable transmission filter at the aperture stop of a lens to modify its diffraction pattern. Reduced transmission at the center of the aperture will favor performance at high...
apogee
The point on an elliptical orbit about the Earth that is the farthest distance from the Earth.
APOMA
American Precision Optics Manufacturers Association
apostilb
A unit of luminance equal to 1/p candela per square meter.
apparent contrast
The perceived brightness difference between light and dark areas on a target.
apparent field
The 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 luminance
The perceived brightness of an object being viewed at some distance, especially through an optical instrument.
apparent movement
The visual perception of motion when fixed stimuli are exposed in rapid temporal and spatial succession.
apparent visual angle
The angle subtended by an object, determined by the size of the object and its distance from the viewer.
APT
automatic picture transmission
aptamer
An 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 humor
The transparent fluid that fills the portion of the eye between the cornea and the eye lens (the anterior chamber).
AR
Abbe refractometer; acoustic radiometer; acoustic resonance; active region; alpha ray; amplitude ratio; antireflective; aperture ratio; applied research; argon; aspect ratio; atomic reactor; augmented reality

Photonics Dictionary

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