The color difference measurement principle of the color-coated plate is to quantitatively measure the color difference between the sample and the reference sample by measuring the spectral tri-stimulus values of the reference sample and the sample. Two types. Among them, the directional geometric structure is divided into 45°/0° and 0°/45°. 45°/0° means that the light irradiates the sample in the 45° direction and the Detector receives the reflected light in the vertical direction, while 0 °/45° refers to the fact that the light receives reflected light at a 45° direction from the irradiated sample in the vertical direction. The instruments of these two structures do not include specular reflection light at all, and the data it measures are consistent with the observation of human eyes. In addition, this instrument can only measure the color of opaque samples; the geometric structure of the integrating sphere is divided into d/8° and 8°/d. The instrument with the integrating sphere structure is that the light irradiates the sample in the horizontal direction, and the Detector receives the reflected or transmitted light at an angle of 8° to the sample. This instrument can not only measure the color of opaque samples but also transparent samples s color.
When measuring, choose standard light source, standard chromaticity observer, color space and observation aperture. Measure the chromaticity coordinates of the reference sample CIELABL, a, b or HunterLab, ab under the specified instrument conditions, and then measure the chromaticity coordinates of three different parts of the sample under the same conditions. If the directional Colorimeter is non-circular For ring lighting, the same measurement point of the reference sample and the sample should be rotated 90° in four directions to measure four chromaticity coordinate values, and the arithmetic mean value is the chromaticity coordinate value of the measurement point.
The color difference between the sample and the reference sample can be calculated by the following formula (see the national standard GB/T 13448-2006 for the specific algorithm):
