8,289 terms
Photonics Dictionary
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LTElocal thermodynamic equivalent
LTHRlateral transfer hollow retroreflector
LTPSlateral transitional phase shift
LTSlaser thermal simulation; laser-triggered switch
lumaThe luminance portion of a composite video signal, i.e., the portion of the signal that corresponds to the brightness of the image apart from any color value, giving a monochrome, or gray scale,...
lumenA lumen is a unit of measurement used to quantify the amount of luminous flux, which is the perceived power of light. In other words, the lumen measures the total amount of visible light emitted by a...
lumen-secondSI unit of quantity of light.
lumiaA laser effect used especially for laser light shows. Lumia are created by placing a distorting medium such as rippled glass in the path of the laser beam.
luminaireA complete unit containing a light source, globe, reflector, housing, socket and other necessary components for lighting.
luminanceLuminous flux emitted from a surface per unit solid angle per unit of area, projected onto a plane normal to the direction of propagation. Also known as brightness and luminous sterance.
luminance factorRatio of the luminance of a specimen to that of a perfect reflecting or transmitting diffuser identically illuminated.
luminance meterA type of photometer calibrated in luminance units (candles per square unit, or lamberts). In photography an exposure meter contains a luminance meter to record the average luminance of a scene.
luminance rangeAn objective measure of an object's brightness that is derived from the ratio of the luminance of its lightest section to that of its darkest section.
luminescenceLuminescence is the emission of light that occurs without the involved substance undergoing a significant increase in temperature. In other words, it is the production and emission of light by a...
luminescent fiberFiber that emits luminescent radiation excited by ultraviolet, x-ray or high-energy particles.
luminescent greenhouse collectorA collector for photovoltaic power generation that consists of a thin plate that strongly absorbs sunlight striking its faces and luminesces efficiently. A large fraction of the luminescence is...
luminosityLuminosity refers to the total amount of energy emitted by an astronomical object, typically measured per unit time. It quantifies the intrinsic brightness of the object and is often expressed in...
luminosity curvePlot of spectral luminous efficiency vs. wavelength.
luminousPertaining to electromagnetic radiation as perceived by the eye; that is, with the contributions as wavelengths in the visible region weighted according to V(λ), which symbolizes the spectral...
luminous efficacyQuotient of total luminous flux divided by total radiant flux; lumens per watt. (For a source, quotient of total luminous flux divided by lamp power input.)
luminous efficiencyRatio of radiant flux weighted according to V(l), the spectral luminous efficiency, to the corresponding radiant flux.
luminous emittanceLuminous flux emitted per unit area of a source, expressed as lumens per area.
luminous energyA measure of the time-integrated amount of flux. It has units of lumen-seconds and might be used to describe such things as the radiant energy that the eye would receive from a photographic flash.
luminous exitanceThe total luminous flux given out per unit area; i.e., the sum of the luminous emittance and any radiation that is reflected from and/or transmitted through the surface: expressed as lumens per area.
luminous fluxDescriptive of the radiant power of visible light modified by the eye response. It is the measure of the flow of visible light energy past any given point in space in a given time period, and is...
luminous paintA mixture of phosphor with a trace of a radioactive element that emits faint light continually. It is used on watch dials and as a marker inside dark rooms to show the location of switches.
Lummer-Brodhun cubeA photometric instrument having two prisms clamped in optical contact to produce a photometric field with an acute dividing line.
Lummer-Gehrcke plateA high-resolution spectroscopic device commonly used in the early 20th century as a component of double-beam interferometers. Light introduced at one end of the plane-parallel glass plate will be...
LUPIlaser unequal path interferometer
luxSI unit of luminous incidence or illuminance, equal to 1 lumen per square meter.
lux-secondSI unit of light exposure.
luxmeterAn illuminometer designed to measure illumination in terms of luxes.
LV-ROMlaser vision read-only memory
LVDSlow-voltage differential signaling
LVDTlinear variable differential transformer
LVNDlaser variable neutral density
LWIRlong-wavelength infrared
LWPlong-wave pass
Lyman continuumA spectrum that is continuous in the UV region with borders ranging from the visible to 300 A and lower.
Lyman ghosts -> GHOSTglobal horizontal and sounding technique
Lyman-alpha radiationThe hydrogen-derived, ultraviolet radiation running from 1216 to 512 A, discovered by Theodore Lyman in 1914.
lymphocyteA lymphocyte is a type of white blood cell (leukocyte) that plays a central role in the immune system. Lymphocytes are produced in the bone marrow and mature in the lymphoid organs, such as the...
Lyot filterA type of filter consisting of a series of birefringent crystals and polarizers invented by French astronomer Bernard Lyot for isolating and observing significant wavelengths of solar light.
Lyot stopA physical stop that is conjugate to the entrance pupil and is used primarily to reduce diffraction effects at longer wavelengths.
melectron rest mass
µmicro- the SI metric unit prefix, which represents one millionth, i.e. 10-6, of a given unit
µmmicron (also referred to as the micrometer)- which represents one millionth, i.e. 10-6 of the SI unit for length that is the meter.
mmeter;mass;milli- m is the standard unit symbol for length in the International System of Units (SI). 1 meter is equivalent to 3.28 feet. m is also the standard symbol for mass; m is also the standard SI metric unit prefix milli- which represents one thousandth i.e. 10-3, of a given unit.
Mmega;magnification -SI metric unit prefix which represents one million, 106, also the standard symbol for the magnification of a given optical system.
mAmilliampere (or milliamp in English) which represents one thousandth, i.e. 10-3, of the SI unit for electric current that is the ampere (also commonly referred to as amp).
Photonics Dictionary