First, the luminous flux:
In a unit of time, the light source radiates into the surrounding space to make the light of the human eye produce light (understand: the light that can make the human eye produce the visible light, so I think it can also be roughly understood as the visible light radiated by the light source to the surrounding space. energy).
When a monochromatic light source having a yellow-green wavelength of 555 nm is emitted, if the radiation power is 1 W, it emits a luminous flux of 680 lm. Thus, the luminous flux of a light source of a certain wavelength can be calculated as follows:
Φλ=680V (λ) Pλ
Where: Φλ—the luminous flux (lm) of the light source with a wavelength of λ; Pλ—the radiation power (W) of the light source with a wavelength of λ; V(λ)—the relative spectral light efficiency of the wavelength of λ light.
The luminous flux of the multi-color source is the sum of the monochromatic luminous fluxes.
Second, the luminous intensity:
The luminous flux of a light source radiating within a solid angle in a particular direction. Referred to as light intensity, symbol I, the unit is candela (cd).
Solid angle: the angle formed by a certain area A on the sphere on the center of the sphere is called the solid angle, expressed as ω, and
ω = A / r2, the unit of solid angle is Sr (sphericality). When A=r2, ω=1Sr, so the solid angle corresponding to the entire spherical surface is ω=4Пr2/r2=4П(Sr).
Therefore, there are: Iθ=Φ/ω Iθ—the light intensity (cd) of the light source in the θ direction; Φ—the luminous flux (lm) received by the spherical surface A; the corresponding solid angle (Sr) of the spherical surface. 1cd=1lm/1Sr
Third, the illumination:
The luminous flux received per unit area of ​​the illuminated object is called the illuminance of the illuminated surface, and the symbol is E, and the unit is lx. Illuminance can be expressed as:
E=Φ/A
Where: E - illuminance on the illuminated surface (lx); Φ - A received light flux (lm); A - the area of ​​the received luminous flux.
When the diameter of the light source is less than 1/5 of its distance to the illuminated surface, the light source can be considered as a point source. The surface illuminance E is proportional to the light intensity Iθ of the point source in this direction, and inversely proportional to the square of the distance r from the source, called the inverse square inverse law.
When the light is obliquely incident, the illuminance of the illuminated surface is proportional to the light intensity Iθ of the light source in this direction and the cosine of the incident angle θ, and inversely proportional to the square of its distance from the light source.
Fourth, the light output:
The luminous flux emitted by a surface light source per unit area to a half space is called the light exiting degree of the light source, and the sign is M, and the unit is lm/m2. Its calculation formula is: M=Φ/S, where S is the area of ​​the surface light source ( M2).
The light emission degree of the secondary light-emitting surface that is reflected and emitted is M=ÏE where Ï is the reflection coefficient of the illuminated surface. The light emission degree of the secondary light-emitting surface that emits light due to transmission is M = Ï„E where Ï„ is the transmission coefficient of the illuminated surface.
Five, brightness:
The luminous intensity of the illuminant in the line-of-sight direction projection area is referred to as the surface luminance of the illuminant, and is represented by the symbol L in units of cd/m2.
Lθ=Iθ/Acosθ, where Lθ is the luminance of the illuminant along the surface (cd/m2), Iθ—the luminous intensity of the illuminant along the direction (cd); Acos θ—the projection surface of the illuminant in the line of sight direction.
Sixth, brightness contrast C:
Ratio of target brightness to background brightness in field of view
Seven, the general color rendering index Ra:
The general color rendering index for daylight and artificial standard light sources close to daylight is set at 100. For the same object, the color developed under the illumination of the measured light source is more consistent with the color developed by the light of the standard light source, and the larger Ra, the better the color rendering performance; conversely, the poorer the color rendering property.
Eight, color temperature:
The color of a light source expressed by a different color emitted by a black body heated to a different temperature is called the color temperature of the light source, and the color temperature is expressed in units of absolute temperature scale K. The correlated color temperature is the radiant temperature at which the chromaticity of the light is closest to or at the minimum of the chromaticity of the complete radiator (black body) at a certain temperature.
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