Color measurement is mainly divided into the measurement of the color of the light source and the measurement of the color of the object. The object color measurement is divided into fluorescent object measurement and non-fluorescent object measurement. In actual production and daily life, color measurement of non-fluorescent objects is widely used. It is mainly divided into two categories: visual color measurement and instrument color measurement. Among them, instrument color measurement includes photoelectric integration method and spectrophotometry method.
1. Visual method
The visual method is the visual perception of light produced by the eyes, the brain, and our life experience. The light we see with the naked eye is generated by electromagnetic waves with a narrow wavelength range, and electromagnetic waves of different wavelengths show different colors The recognition of color is the visual nerve sensation caused by the naked eye after being stimulated by electromagnetic wave radiation energy.
The unknown colors of the individual components are added together to describe the resulting unknown colors. Although it is most suitable for color evaluation. The way to rely on it is with the help of the human eye, and it is simple and flexible, but due to the experience of observers and psychological and physiological factors The impact of this method makes the method too many variables and cannot be described quantitatively, which affects the accuracy of the evaluation.
2.The photoelectric integration method
For a long time, the density method has occupied a very high position in color measurement, but with the application of CIE1976L *, a *, b * gradually becoming widespread, and has covered the entire work flow from press to printing, people are more and more aware of color The importance of degree, and the rapid development of modern colorimetric have also laid the foundation for the objective evaluation of color by photoelectric integration instruments ( precision color difference meters).
The photoelectric integration method is a common method used in instrument color measurement in the 1960s. It does not measure the color stimulus value of a certain wavelength, but measures the tristimulus values X, Y, and Z of the sample through integral measurement over the entire measurement wavelength interval, and then calculates the chromaticity coordinates and other parameters of the sample. When using such three photo detectors to receive light stimuli, the tristimulus values X, Y, and Z of the sample can be measured with one integration. The filter must meet Luther's conditions to accurately match the photo detector.
The photoelectric integration instrument cannot accurately measure the tristimulus value and chromaticity coordinates of the excellent source, but can accurately measure the color difference between the two color sources, so it is also called a color difference meter. Foreign color difference meters have been mass-produced since the 1960s, and China has been developing such instruments since the early 1980s. Nowadays, the CS-210 precsision colorimeter produced by Hangzhou CHNSpec Technology Co.,Ltd has been used.
Spectrophotometry is also called spectrophotometer. It compares the light energy reflected (transmitted) by the sample with the standard reflected (transmitted) light energy under the same conditions to obtain the spectral reflectance of the sample at each wavelength, and then uses CIE The provided standard observer and standard light source are calculated according to the following formula to obtain the tristimulus values X, Y, and Z, and then X, Y, and Z are used to calculate the chromaticity coordinates x according to the formulas such as CIE Yxy and CIE Lab. y, CIELAB chromaticity parameters, etc.
The spectrophotometer determines the color parameters by detecting the spectral components of the sample. It can not only give the absolute values of X, Y, Z and the color difference value △ E, but also give the spectral reflectance value of the object, and can draw the object. Therefore, it is widely used in color matching and color analysis. The use of such instruments can achieve high-accuracy color measurement, calibration of photoelectric integral color measurement instruments, and establishment of chromaticity standards. Such instruments were first developed in China. CS-600 Integrating Sphere Color Spectrophotometer is color spectrum. Therefore, the spectrophotometer is an authoritative instrument in color measurement.
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