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Photonics Dictionary

extramural absorption cement
A cement used to reduce crosstalk in fiber optic bundles or plates.
extraordinary ray
A ray that has a nonisotropic speed in a doubly refracting crystal. It does not necessarily obey Snell's law upon refraction at the crystal surface.
extraterrestrial radiation
Radiation that is emitted by a source outside the Earth and its atmosphere.
extreme ultraviolet
Extreme ultraviolet (EUV) refers to a specific range of electromagnetic radiation in the ultraviolet part of the spectrum. EUV radiation has wavelengths between 10 and 124 nanometers, which...
extrinsic detector
A photodetector composed of a semiconductor material whose responsive properties can be altered by the addition of impurities to the basic material. Copper- and mercury-doped germanium are both...
extrinsic fiber loss
A type of optical fiber loss resulting from the misalignment of fibers in a splice or connector.
extrinsic joint loss
Synonym of extrinsic fiber loss.
extrinsic photoconductivity
Photoconductivity due to the addition of impurities or external causes.
extrinsic properties
The properties exhibited by a semiconductor as the result of its modification by imperfections and impurities in the crystal.
eye
The organ of vision or light sensitivity.
eye box
The area in a 2-D or 3-D microdisplay viewer within which the eye can move and still see the entire image.
eye distance -> eye relief
Also termed eye distance. The distance between the vertex of the last optical surface of a visual optical system and the system's exit pupil.
eye guard
A shield of rubber, plastic or metal used to protect the eyes of the observer from stray light and wind, and to maintain the proper eye distance.
eye lens
The lens of an eyepiece nearest the observer's eye.
eye pattern
A pattern on an oscilloscope display that consists of a string of shapes that resemble eyes. Because the pattern becomes more closed with increasing distortion and interference, an open eye diagram...
eye relief
Also termed eye distance. The distance between the vertex of the last optical surface of a visual optical system and the system's exit pupil.
eye shield -> eye guard
A shield of rubber, plastic or metal used to protect the eyes of the observer from stray light and wind, and to maintain the proper eye distance.
eye test apparatus
Instruments used by ophthalmologists and optometrists to study the eye. There are, for instance, the ophthalmoscope to observe and photograph the retina; the retinoscope and optometer to determine...
eye tracker
An optical device used to monitor movement of the human eye.
eye-safe laser operation
Wavelengths between 400 and 1400 nm (VIS to NIR) are focused onto the retina by the cornea. Because the retina is sensitive to light, these wavelengths can be damaging even at low energies. It is the...
eyepiece
Also known as ocular. The lens system used between the final real image in a visual optical system and eye. It acts as an image magnifier. Many types of eyepieces are known; e.g., the Huygens used in...
eyepiece micrometer -> measuring eyepiece
Also known as an eyepiece micrometer. A microscope eyepiece that has a finely divided scale ruled or photographed on a section of transparent glass, and located in the focal plane. The dimensions of...
f number (f/#)
The expression denoting the ratio of the equivalent focal length of a lens to the diameter of its entrance pupil.
f/#
f number
f
focal length; femto-
F
Farad; Fahrenheit
f-Theta lens
An f-theta lens, also known as an f-theta scan lens or simply an f-theta lens system, is a specialized optical component used in laser scanning systems, particularly in laser marking, engraving, and...
F-center -> color center
A color center, in the context of materials science and condensed matter physics, refers to a specific type of crystallographic defect in a crystalline structure that introduces color to the...
FAB
fast atom beam
Fabry-Perot cavity
An optical resonator in which feedback is accomplished by two parallel planes. In diode lasers, the planes are obtained by cleaving, polishing, etching, etc.
Fabry-Perot etalon
A nonabsorbing, multireflecting device, similar in design to the Fabry-Perot interferometer, that serves as a multilayer, narrow-bandpass filter.
Fabry-Perot fringes
The series of rings when monochromatic light passes through a Fabry-Perot interferometer.
Fabry-Perot interferometer
A multiple-beam interferometer, usually consisting of two flat plates, with high reflective ability. The plates are set parallel to one another by spacers so that lightwaves may bounce back and forth...
Fabry-Perot laser
A laser oscillator in which two mirrors are separated by an amplifying medium with an inverted population, making a Fabry-Perot cavity. Standard diode lasers are Fabry-Perot lasers.
Fabry-Perot method
A means of determining a prism's index of refraction by placing the prism so that its emergent face is perpendicular to the incident beam. This arrangement permits the determination of the prism's...
Fabry-Perot mirror
A highly reflective mirror that is usually flat on one surface and curved on the other, and that has silver, gold or aluminum deposited on glass, providing about 99 percent reflection.
Fabry-Perot spectroscopy
The spectroscopic analysis of interference patterns using a monochannel spectrometer, spectrograph or multichannel spectrometer with a Fabry-Perot interferometer to record the fringes.
face-centered
With respect to a unit cell in a crystal structure, the property defining an atom located at the center of each face.
face-pumped laser
A device in which slab geometry internally compensates for thermal-optic distortion; the solid host material -- glass or Nd:YAG -- is in the form of a rectangular slab with plane parallel faces. The...
faceplate -> fiber optic faceplate
A plate made up of thousands of glass fibers arranged parallel to one another, i.e., in a coherent bundle, and fused together so that it is hermetically tight. It transfers an image from one plane to...
facet
1. One of the plane-reflecting surfaces on a multisurfaced polygon. 2. The cleaved end mirror of a laser diode's active region.
facet erosion
The degradation of the facets in a laser diode due to the intensity of radiation.
facsimile chart
Data gathered by a facsimile system and converted into graphic, readable form; generally used in meteorology. Also known as fax chart or fax map.
facsimile machine
A device used to transmit and receive images that have been converted to electrical signals over regular telephone lines; it includes a scanner, a transmitter, a receiver and a printer.
facsimile radio
The conversion of a still picture into sound waves and its subsequent transmission by radio.
facsimile synchronizing
The maintenance of the same scanning relationship between the transmitting scanning spot and receiving scanning spot for each scanning line transmitted in a facsimile system.
facsimile
The reproduction of a picture or image, produced by scanning the image and converting it into electrical signals that carry the image to be reproduced. Also known as fax.
fall time
Measurement of the interval during which a photodetector's signal and output current drops from 90 to 10 percent.
false Becke line
A secondary halo whose movement counterpoints the behavior of the Becke line.
false color
In imaging technology, assigning color to black and white images to differentiate features or convey information. Also called colorizing.

Photonics Dictionary

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