Distribution temperature
(distribution temperature) T d
When the relative spectral radiation power distribution of the radiation source at temperature T is the same as the relative spectral radiation power distribution of the black body at a certain temperature Td, the temperature Td of the black body is called the distribution temperature of the radiation source. Since the light with the same spectral distribution must have the same color, the chromaticity coordinates of the black body and the radiation source on the CIE 1931 chromaticity diagram must coincide.
Of course, the radiation of the actual non-black body radiation source cannot be completely consistent with the relative spectral radiant power distribution of the black body, but when the error is less than ±5% or the relative spectral radiant power distribution of the two is largely the same, it can be The distribution temperature of the radiation source is characterized by the temperature Td of the black body.
color temperature
(color temperature) T c
When the color of the radiation source at temperature T is the same as that of the black body at a certain temperature Tc, the temperature Tc of the black body is called the color temperature of the radiation source (referred to as color temperature).
For thermal radiation sources such as incandescent lamps, because their spectral distribution is relatively close to that of black bodies, their chromaticity coordinates are basically on the black body locus, and the concept of visible color temperature can properly describe the light color of incandescent lamps. Generally, a higher color temperature means more components of blue and green light; a lower color temperature means more components of orange and red light.
In addition, since the distribution temperature corresponds to the spectral distribution of the radiation source, and the light with the same spectral distribution must have the same color, the distribution temperature must be the color temperature.
correlated color temperature
(correlated color temperature) T cp
For some commonly used radiation sources other than incandescent lamps, their spectral distribution is far from that of a black body, and the chromaticity coordinates determined by their relative spectral power distribution at temperature T may not exactly fall on the blackbody temperature locus of the chromaticity diagram , and in the vicinity of the trajectory. At this time, the aforementioned color temperature cannot be used to describe its color, but the concept of correlated color temperature needs to be used to characterize and compare the light color characteristics of this type of radiation source. When the color of the radiation source is closer to the color of the black body at a certain temperature, or when the distance between the two coordinate points on the chromaticity diagram is the smallest, the temperature of the black body can be used to represent the color temperature of the radiation source, and it is called It is the correlated color temperature of the radiation source, usually represented by the symbol Tcp. Table 1 lists the correlated color temperature of common illuminants in daily life.
