Like all the colors in nature, the optical radiation of led device will produce visual stimulation to human eyes. People evaluate LED characteristics of color based on their own feelings. In order to avoid the subjectivity of this evaluation, physical method should be used to the color measurement ( colorimeter ).
At present, there are some problems such as the misuse of the term in the actual application; therefore, it is necessary to discuss the LED device chromaticity measurement issues for reference.
The Mental Attributes and Terms of Color
According to the appearance of color and the mental feeling for the intuitionistic color vision, people conducted the systematic introduction and arrangement for colors, and did the corresponding text description and figure mark. Color can be divided into color and achromatic color. Achromatic color refers to white, black and all kinds of different shades of gray, which have constituted a so-called black and white series. The research shows that there are three kinds of mental characteristics, which can be described by using tone, saturation and brightness ( Brightness Meter ).
It refers to the attributes of the discriminating colors. The optical radiation of different wavelengths in the visible light spectrum displays different tones such as red, green, blue and yellow etc. The tone of the light source depends on the feelings of the human eyes for the radiant spectrum composition. However, the tones of the object depend on the feelings for the light source composition and the radiation ratio of each wavelength reflected (or transmitted) by the body surface.
It refers to the purity of the color. In the visible spectrum, each monochromatic light has the highest saturation. The saturation is lower by mixing more white light with the monochromatic light.
Brightness is the bright degree of the color that human eyes can feel. The brightness is higher, human eyes will feel brighter, namely the brightness is higher. The luminous reflectance change of the achromatic color subject in the black and white series is the brightness changes. The visible color is more close to white, the brightness is higher.