Basic knowledge of optics - a collection of terms

Do you have the basic terms of optics memorized? If not, read here.

Correlated Color Temperature: If the color of light emitted by a light source is closest to the color of light radiated by a black body at a certain temperature, then the temperature of the black body is called the correlated color temperature of the light emitted by the light source, and the unit is K.

Radiant Intensity: The radiant flux dφ emitted by a radiation source within a solid angle element containing the direction in a given direction divided by the solid angle element dΩ, with the unit of W/Sr.

Radiance: The radiation intensity dl of the surface element dA containing a point on the radiation source surface in a given direction divided by the orthographic projection area of ​​the surface element on the plane perpendicular to the given direction, with the unit of W/Sr?m2.

Irradiance: The irradiance E at a point on the radiation receiving surface is equal to the radiation flux dφ projected on a surface element including the point divided by the area dA of the surface element, and the unit is W/m2.

Luminous Intensity: The luminous flux dφ emitted by a light source in a given direction within a solid angle element including that direction divided by the solid angle element dΩ, in cd.

Candela (cd): Unit of luminous intensity. Candela is the luminous intensity of a light source emitting radiation with a frequency of 540×1012Hz in a given direction; the radiant intensity of the light source in this direction is 1/683W/Sr.

Luminous Flux: The amount of light radiation power that can be sensed by the human visual system, measured in lm.

Illuminance: The illuminance at a point on a surface is the luminous flux dφ incident on the surface element containing the point divided by the surface element area dA. The metric unit of illuminance is lx (lm/m2) and the imperial unit is fc (lm/ft2).

1lx=0.0929fc

1fc=10.76lx

Luminous Exitance: The luminous flux emitted per unit area, the unit is lm/m2.

Luminance: The luminous intensity per unit area in a given direction. The metric unit of luminance is cd/m2 (also called Nit), and the imperial unit is fL (1/π×cd/ft2).

1cd/m2=0.2919fL

1fL=3.426cd/m2

CIE STandard Photometric Observer: An ideal observer whose relative spectral response curve conforms to the photopic V(λ) function or the scotopic V' (λ) function.

Lambertian Surface: The luminous intensity in a certain direction is equal to the luminous intensity in the direction perpendicular to the surface multiplied by the cosine of the direction angle. Such a luminous surface is called a Lambertian emitting surface or a Lambertian body, sometimes also called a uniform diffuse surface or a uniform diffuser, and often called a cosine diffuser. The relationship between the luminous intensity and brightness of a Lambertian emitting surface is M=πL.

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