Specializing in lighting for 20 years

# Common lighting terms (Part I)

Date:04-01-2018

In order to get good lighting, it is necessary to have a reasonable lighting design. Reasonable lighting design should meet applicable requirements, safety, eye protection and economic requirements, and strive to achieve a comfortable lighting environment.

Experiments show that the normal wavelength of 555nm yellow-green light is the most sensitive, so the more deviation from the wavelength of 555nm radiation, the smaller the visibility.

First, the luminous flux:

The unit of time, the light source to the surrounding space can make the human eye light perception of energy (understanding: can make the human eye sense of light as visible light, so I think it can be generally understood as the light source to the surrounding space of visible light energy).

When emitting a monochromatic light source with a wavelength of 555 nm yellow-green, if the radiated power is 1 W, it emits a luminous flux of 680 lm. From this, it can be concluded that the light flux of a light source with a certain wavelength is calculated as follows:

Φλ = 680V (λ) Pλ

Wherein: Φλ - luminous flux (lm) of a light source with wavelength λ; Pλ - radiant power (W) of a light source with wavelength λ; V (λ) - relative spectral efficiency of light with wavelength λ.

Multi-color light flux for the monochromatic light flux and the sum of.

Second, luminous intensity:

Light source in a particular direction of solid cube within the luminous flux of radiation. Referred to as light intensity, symbol I, the unit is Candela (cd).

Stereo angle: a piece of sphere A area of the center of the ball angle is called the solid angle, expressed in ω, and

ω = A / r2, and solid angle unit is Sr (spherical surface degree). When A = r2 ω = 1Sr so the entire spherical surface corresponding to the solid angle ω = 4Пr2 / r2 = 4П (Sr).

So there: Iθ = Φ / ω Iθ-light source in the θ direction of the light intensity (cd); Φ-spherical A accepted luminous flux (lm); spherical corresponding solid angle (Sr). 1cd = 1lm / 1Sr

Third, illumination:
According to the object unit area accepted by the luminous flux is called according to the illuminance of illumination, symbol E, the unit is lx. Illumination can be expressed as:
E = Φ / A
Where: E-illuminated surface illumination (lx); Φ-A area to accept the luminous flux (lm); A- accept the luminous flux of the area.
When the light source diameter is less than 1/5 of its distance from the illuminated surface, the light source can be regarded as a point light source. The surface illuminance E is proportional to the intensity Iθ of the point source in this direction and inversely proportional to the square of the distance r to the light source and is called the inverse square distance law.
When 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 incidence angle θ, inversely proportional to the square of the distance from the light source to the light source.

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