400 terms
Photonics Dictionary: E
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equivalent air pathWhen a block of glass (prism, window, filter, etc.) is placed into a converging light bundle, it increases the physical distance to the point of focus. The equivalent air path for that block of glass...
equivalent focal length -> focal lengthThe 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...
equivalent wavelengthIn surface height measurement of optics with steep slopes, the use of two short visible wavelengths to synthesize a longer, equivalent wavelength.
Er:YAG laserAn Er:YAG laser is a type of solid-state laser that uses a crystal made of erbium-doped yttrium aluminum garnet (Er:Y3Al5O12) as the gain medium. The erbium (Er) ions are introduced into the crystal...
ERAearth radiation array
erasableData or encoded information capable of being eradicated, leaving the media free for rewriting. Also called reversible.
erbium-doped fiber amplifierAn optical fiber that can be used to amplify an optical input. Erbium rare earth ions are added to the fiber core material as a dopant in typical levels of a few hundred parts per million. The fiber...
ERCRelectronic retina computing reader
erect imageAn image, real or virtual, whose spatial orientation is identical to that of the object. The image obtained at the retina with the assistance of an optical system is said to be erect when the...
erecting eyepieceAn eyepiece combined with an erecting prism or lens system.
erecting systemLenses or prisms that serve to erect the image; i.e., to bring the image upright after it has been inverted by the objective.
Erfle eyepieceA telescopic eyepiece comprising five or six simple lenses in the form of three doublets or two doublets and a singlet.
ERGelectroretinography
erosionIn image processing, a morphology operator in which a structuring element or probe of a particular shape is moved over the input image. Where the probe fits completely within the boundaries of a...
ERPeffective radiated power
error correcting codeThe addition to the information signal in communications of redundant bits that enable the originally encoded message to be decoded without degradation of the data. In compact disc technology, the...
error functionA single number, defined by the computer program or the user that expresses the performance of an optical system. Also known as merit function and defect function, the error function comprises...
ERTSearth resources technology satellite
erythemaLocalized redness of skin due to congestion of capillaries; a common result of overexposure to laser radiation.
ESAEuropean Space Agency; excited state absorption
ESCAelectron spectroscopy for chemical analysis
ESDelectrostatic discharge
ESFextended superframe format
ESPIelectron speckle pattern interferometry
ESPRITEuropean Strategic Programme for Research in Information Technology
ESRelectrical substitution radiometer; electron spin resonance
ESSAenvironmental survey satellite
ESTMelectron scanning tunneling microscope
esuelectrostatic unit
etalonAn etalon is an optical device that consists of two parallel reflecting surfaces separated by a precise and known distance. It operates based on the principle of optical interference and is used to...
etaloningEtaloning is an optical phenomenon that occurs in imaging systems, particularly in devices such as spectrometers, interferometers, and cameras. It is characterized by the appearance of interference...
etchingThe engraving of a surface by acid, acid fumes or a tool; a process extensively used in the manufacture of reticles.
etching liquidAn acid used to etch the surfaces of particular materials. For glass, hydrofluoric acid is used either as a liquid or a vapor. Metals are etched by means of suitable acids or other liquids, often to...
etendueA product of the area of a light beam (normal to its direction of propagation) and the solid angle that the beam includes; flux per unit radiance or luminance. Alternative terms: geometric extent,...
ETIRenvironmental thermal infrared
ETOMelectron trapping optical memory
eutecticThe material that has the lowest possible constant melting point of any possible combination of the same components.
EUVextreme ultraviolet
evanescent field theoryA high-frequency approach to the propagation of light in graded-index fibers in which the modal field is represented in terms of an inhomogeneous (evanescent) plane wave with a complex phase, so that...
evaporagraphA sensor generally used for infrared imaging. It consists of two chambers separated by a thin, blackened membrane. An infrared image is formed on the membrane by a lens or mirror and produces...
evaporation coatingCoating carried out in a sealed chamber evacuated by a mechanical pump in series with an oil diffusion pump to a pressure less than 10-4 mm of mercury, measured by a vacuum gauge. At such a low...
evapotranspirationA process, either naturally occurring or mechanically induced, whereby water is changed from its liquid state into a vapor.
event-based sensorAn event-based image sensor, also known as a dynamic vision sensor (DVS), is a type of digital imaging device designed to capture visual information in a highly efficient and unique way compared to...
EWelectronic warfare; early warning
EWACSelectronic wide-angle camera system
EXAFSextended x-ray absorption edge fine structure
excess noise factorA factor, F, indicating the increase in shot noise in an avalanche photodiode as compared with the ideal multiplier, which is noiseless. The noise, which results from variations in avalanche gains,...
excimerA contraction of "excited dimer." The term refers to an excited species made by combination of two identical atoms or molecules, one of which is excited and one of which is at a ground...
excimer laserAn excimer laser is a type of ultraviolet laser that emits short pulses of light in the ultraviolet spectrum. The term excimer is derived from excited dimer, reflecting the nature of the gain medium...
excimer laser coronary angioplastyExcimer laser coronary angioplasty (ELCA) refers to a medical procedure used in the treatment of coronary artery disease. This technique involves the use of an excimer laser to perform angioplasty, a...
Photonics DictionaryE