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Photonics Dictionary: F

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friability
The resistance of individual grains of an abrasive to breaking down under pressure. If the grains break down under relatively low pressure, the abrasive is said to be more friable.
Fried length
The length of the small space within which the atmosphere exhibits coherence, particularly in relation to an observer on Earth viewing celestial objects. The turbulence of the Earth's atmosphere...
Fried's seeing parameter
A calculated function that can be achieved experimentally with interferometric analysis of complex atmospheric altitude; expressed as a relation to the turbulence integrated over the entire...
fringe
An interference band such as Newton's ring.
fringes of superposition
The multiple beam form of Brewster's fringes formed when the two plane-parallel plates have high-reflecting surfaces.
front focal length -> focal length
The focal length of a lens is the distance between the lens's optical center (or principal point) and the image sensor or film when the lens is focused at infinity. In simple terms, it is the...
front operating aperture
The restricting aperture located at the front of the lens. It is usually defined as the maximum diameter of the entrance cone at the front vertex, for the specified field of view at infinity focus.
front porch
In communcations and video signals, the portion of a composite signal between the leading edge of the horizontal blanking pulse and the leading edge of the horizontal synchronization pulse.
front vertex focal distance
The distance between the front focal point and the vertex of the front surface.
front-cell focusing
A method of focusing an optical system by moving the front component (the lens closest to the subject) to change the distances between components. Also known as front-element focusing.
front-surface mirror
An optical reflector with the reflective coating applied to the front surface of the substrate. This eliminates the ghost image formed with second-surface mirrors.
frustrated total reflection
Light leakage at a total reflecting interface when another highly refractive medium is brought close to it.
fs
femtosecond
FSDO
free-space digital optical
FSK
frequency shift keying
FSM
fast steering mirror
FSO
free-space optics
FSR
free spectral range
FSS
flying spot scanners
FT
Fourier transform
ft lb
foot pound
FTC
field test collimator
FTCCD
field transfer charge-coupled device
FTIR
Fourier transform infrared; frustrated total internal reflection
FTIR spectrometer
FTIR (Fourier transform infrared) spectrometer is a powerful analytical instrument used to obtain an infrared spectrum of absorption or emission of a solid, liquid, or gas sample. It operates based...
FTPSI
Fourier transfer phase-shifting interferometry
FTS
Fourier transform spectroscopy
FTTC
fiber to the curb
FTTH
fiber to the home
full duplex -> duplex
In data communications, the simultaneous operation of a circuit in both directions is known as full duplex; if only one transmitter can send at a time, the system is called half duplex.
full duration half maximum -> full width half maximum
The full width at half maximum (FWHM) is a measure used in various fields, particularly in spectroscopy, signal processing, and imaging, to characterize the width or extent of a distribution, peak,...
full radiator -> blackbody
An ideal body that completely absorbs all radiant energy striking it and, therefore, appears perfectly black at all wavelengths. The radiation emitted by such a body when heated is referred to as...
full wave compensator
A piece of uniform birefringent material placed at a 45° angle to the plane of polarization in a polarizing microscope to indicate changes in color caused by interference when a birefringent...
full width half maximum
The full width at half maximum (FWHM) is a measure used in various fields, particularly in spectroscopy, signal processing, and imaging, to characterize the width or extent of a distribution, peak,...
full-well capacity
The number of electrons that each pixel of a charge-coupled device can hold without overflowing and causing blooming.
fullerenes
Molecules composed entirely of carbon, in the form of a hollow sphere, ellipsoid or tube. Also called buckyballs. Cylindrical fullerenes are called carbon nanotubes or buckytubes.
function generator
A computer hardware unit that generates required functional information on the screen by controlling CRT beam movements or intensity.
functional material
Functional materials refer to materials that possess specific properties or functionalities that make them suitable for particular applications or purposes. These materials are designed and...
functional near-infrared spectroscopy
Functional near-infrared spectroscopy (fNIRS) is a non-invasive neuroimaging technique that measures changes in hemoglobin concentration in the brain. It utilizes near-infrared light to penetrate the...
fundamental mode
The lowest order mode of a waveguide. In fibers, the mode designated LP01 or HE11.
furnace
See glass annealing furnace; glass melting furnace.
fused array of fibers
Optical fibers fused together to form a solid, vacuum-tight assembly in the form of a slab or rod. Discs or rectangular shapes having ground and polished surfaces perpendicular to the fiber lengths...
fused quartz and silica
Fused quartz and silica are closely related materials, both composed primarily of silicon dioxide (SiO2), but they are produced through different manufacturing processes and have distinct properties...
fused silica
Glass consisting of almost pure silicon dioxide (SiO2). Also called vitreous silica. Frequently used in optical fibers and windows.
fusing
The permanent uniting of two glass pieces by high-temperature heating.
fusion
1. The combination of the effects of two or more stimuli in any given sense to form a single sensation. With respect to vision, the perception of continuous illumination formed by the rapid...
fusion ignition
Fusion ignition refers to the point in a controlled nuclear fusion reaction where the energy released by the fusion reactions becomes self-sustaining, leading to a continuous release of energy...
fusion splice
A splice accomplished by the application of localized heat sufficient to fuse or melt the ends of two lengths of optical fiber, forming a continuous single fiber.
FVD
front vertex focal distance
FWA
fluorescent whitening agents

Photonics DictionaryF

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