光束

WordNet

a measure of luminous flux per unit area
a state of uncertainty about what should be done (usually following some important event) preceding the establishment of a new direction of action; "the flux following the death of the emperor" (同)state of flux
a substance added to molten metals to bond with impurities that can then be readily removed
excessive discharge of liquid from a cavity or organ (as in watery diarrhea)
the rate of flow of energy or particles across a given surface
in constant change; "his opinions are in flux"; "the newness and flux of the computer industry"
a flow or discharge (同)fluxion

PrepTutorEJDIC

流動,流れ;上げ潮 / 絶え間ない変化,流転(るてん) / 融剤,フラックス / (流体・粒子・エネルギーの)流量,流束,流動率 / (電気・磁気の)束(そく) / (体内の液体の)異常流出,異常排出
『光を発する』,光る,輝く(shining);明るい(bright) / 明白な(clear),分かりやすい
インフルエンザ,流感

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/08/15 14:59:09」(JST)

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Photopic (black) and scotopic ^[1] (green) luminosity functions. The photopic includes the CIE 1931 standard (solid),^[2] the Judd-Vos 1978 modified data (dashed),^[3] and the Sharpe, Stockman, Jagla & Jägle 2005 data (dotted).^[4] The horizontal axis is wavelength in nm.

Integrating sphere used for measuring the luminous flux of a light source.

In photometry, luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of electromagnetic radiation (including infrared, ultraviolet, and visible light), in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.

Units

The SI unit of luminous flux is the lumen (lm). One lumen is defined as the luminous flux of light produced by a light source that emits one candela of luminous intensity over a solid angle of one steradian. In other systems of units, luminous flux may have units of power.

Weighting

The luminous flux accounts for the sensitivity of the eye by weighting the power at each wavelength with the luminosity function, which represents the eye's response to different wavelengths. The luminous flux is a weighted sum of the power at all wavelengths in the visible band. Light outside the visible band does not contribute. The ratio of the total luminous flux to the radiant flux is called the luminous efficacy.

Context

Luminous flux is often used as an objective measure of the useful light emitted by a light source, and is typically reported on the packaging for light bulbs, although it is not always prominent. Consumers commonly compare the luminous flux of different light bulbs since it provides an estimate of the apparent amount of light the bulb will produce, and a lightbulb with a higher ratio of luminous flux to consumed power is more efficient.

Luminous flux is not used to compare brightness, as this is a subjective perception which varies according to the distance from the light source and the angular spread of the light from the source.

Relationship to luminous intensity

Luminous flux (in lumens) is a measure of the total amount of light a lamp puts out. The luminous intensity (in candelas) is a measure of how bright the beam in a particular direction is. If a lamp has a 1 lumen bulb and the optics of the lamp are set up to focus the light evenly into a 1 steradian beam, then the beam would have a luminous intensity of 1 candela. If the optics were changed to concentrate the beam into 1/2 steradian then the source would have a luminous intensity of 2 candela. The resulting beam is narrower and brighter, however the luminous flux remains the same.

SI photometry quantities

Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 1]}	Name	Symbol	Symbol	Notes
Luminous energy	Q_v ^{[nb 2]}	lumen second	lm⋅s	T⋅J ^{[nb 3]}	Units are sometimes called talbots.
Luminous flux / luminous power	Φ_v ^{[nb 2]}	lumen (= cd⋅sr)	lm	J ^{[nb 3]}	Luminous energy per unit time.
Luminous intensity	I_v	candela (= lm/sr)	cd	J ^{[nb 3]}	Luminous flux per unit solid angle.
Luminance	L_v	candela per square metre	cd/m²	L⁻²⋅J	Luminous flux per unit solid angle per unit projected source area. Units are sometimes called nits.
Illuminance	E_v	lux (= lm/m²)	lx	L⁻²⋅J	Luminous flux incident on a surface.
Luminous exitance / luminous emittance	M_v	lux	lx	L⁻²⋅J	Luminous flux emitted from a surface.
Luminous exposure	H_v	lux second	lx⋅s	L⁻²⋅T⋅J
Luminous energy density	ω_v	lumen second per cubic metre	lm⋅s⋅m⁻³	L⁻³⋅T⋅J
Luminous efficacy	η ^{[nb 2]}	lumen per watt	lm/W	M⁻¹⋅L⁻²⋅T³⋅J	Ratio of luminous flux to radiant flux or power consumption, depending on context.
Luminous efficiency / luminous coefficient	V			1
See also: SI · Photometry · Radiometry

^ Standards organizations recommend that photometric quantities be denoted with a suffix "v" (for "visual") to avoid confusion with radiometric or photon quantities. For example: USA Standard Letter Symbols for Illuminating Engineering USAS Z7.1-1967, Y10.18-1967
^ ^a ^b ^c Alternative symbols sometimes seen: W for luminous energy, P or F for luminous flux, and ρ or K for luminous efficacy.
^ ^a ^b ^c "J" here is the symbol for the dimension of luminous intensity, not the symbol for the unit joules.

Examples

**Table of comparative luminous flux of several light sources**^[5]^[6]^[7]
Source	Luminous flux (lumens)
37 mW "Superbright" white LED	0.20
15 mW green laser (532 nm wavelength)	8.4
1 W high-output white LED	25–120
Kerosene lantern	100
40 W incandescent lamp at 230 volts	325
7 W high-output white LED	450
6 W COB filament LED lamp	600
18 W fluorescent lamp	1250
100 W incandescent lamp	1750
40 W fluorescent lamp	2800
35 W xenon bulb	2200–3200
100 W fluorescent lamp	8000
127 W low pressure sodium vapor lamp	25000
400 W metal-halide lamp	40000
Values are given for newly manufactured sources. The output from many sources decreases significantly over their lifetime.

References

^ http://www.cvrl.org/database/text/lum/scvl.htm
^ http://www.cvrl.org/database/text/cmfs/ciexyz31.htm
^ http://www.cvrl.org/database/text/lum/vljv.htm
^ "Sharpe, Stockman, Jagla & Jägle (2005) 2-deg V*(l) luminous efficiency function". Archived from the original on 2007-09-27. Retrieved 2007-05-10.
^ Szokolay, S. V. (2008). Introduction to Architectural Science: The Basis of Sustainable Design (Second ed.). Routledge. p. 143. ISBN 9780750687041.
^ BeLight. 3. Trendforce. 2010. pp. 10–12.
^ Jahne, Bernd (2004). Practical Handbook on Image Processing for Scientific and Technical Applications (Second ed.). CRC. p. 111. ISBN 9780849390302.

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