On the principle of color measurement and color matching

Color measurement principle:
Color is a psychophysical quantity. People’s perception of color is realized by the light signal reflected or transmitted from the object received by the human eye. Color property is a three variable function, which can be described by the three elements of color: lightness, hue, and color saturation. The color of the light source is determined by the spectral distribution of the light source. The color of an object is determined by the spectral characteristics of its surface. However, the human eye does not always have the same color perception for objects with the same spectral characteristics of the object surface. Another key factor affecting the color perception of the human eye is the geometric characteristics of the spatial distribution of light on the object surface. The description of geometric characteristics is relatively complex, and different industries have different concerns. They also use different description and measurement methods, such as object surface glossiness, orange peel, etc.

When the light incident on the object surface, the following four conditions will occur:
1. Specular reflection occurs on the object surface. It is the main reason for the surface luster of objects.
2. When the light incident into the interior of the object, scattering occurs in the interior of the object, resulting in diffuse reflection and diffuse transmission.
3. When diffuse reflection and diffuse transmission light propagate in the object, light of different wave bands will have different absorption, thus producing different colors from the incident light.
4. When the object is more transparent, part of the light will directly pass through the object to generate transmission.

When the light incident on the surface of the object, part of the light reflected on the surface of the object and did not enter the interior of the object. The amount of specular reflected light depends on the refractive index of the object material and the incident angle of light, which follows Fresnel’s law.

The direction of specular reflected light depends on the smoothness of the object surface. With different surface roughness, specular light will produce different spatial distributions as shown in Figure 1.2. For specular light, there is no corresponding absorption because it does not propagate inside the object. Therefore, the spectral distribution of specular reflected light is consistent with that of incident light. The light entering the object is a refracted beam, and the direction of propagation inside the object follows the law of refraction. Refracted light generates multiple reflections and refractions inside the object. When light propagates inside an object, the object’s selective absorption of the spectrum reflects the corresponding color of the object. The light that part of the light returns to the air after passing through the object surface becomes diffuse reflection light, and the other part of the light passes through the object to the lower surface and becomes diffuse transmission light. Diffuse reflected light and diffuse transmitted light are different from the light source spectrum. The specular reflected light and diffuse reflected light are received by the human eye together. If the proportion of specular reflected light in the light signal received by the human eye is too large, the color of the object surface itself will be “diluted”, making the human eye feel that the color brightness is high and the saturation is low.

People must observe color under three conditions: light source, object and eye. Similarly, for the color measuring instrument to obtain the test results, there must be three conditions: lighting source, tested sample and sensor. Up to now, object color measuring instruments have been used to measure color data by measuring the spectral characteristics of material surfaces.

To represent a color objectively and quantitatively, it is necessary to calculate the proportion of the color of the object or light source in the matching stimulus primary colors, that is, calculate the tristimulus value of this color according to the principle of modern colorimetry. The calculation method of tristimulus value is to use the spectral reflection value of the sample, the relative spectral power distribution of the standard illuminant used and the color matching function of the 2 ° or 10 ° field of view recommended by CIE to calculate the chromaticity coordinates and other relevant chromaticity parameters of the sample color by using the equal wavelength interval method within the visible light spectrum range.

Color matching principle:
The colors can be simply classified as red, orange, yellow, green, blue, purple, black and white. The color can be determined by three parameters: hue, lightness and saturation. The colors can vary greatly, but the most basic ones are red, yellow and blue, also known as the three primary colors; Orange, purple and green are the three intermediate colors; The color mixed by the above colors in different proportions is called multicolor.

The color matching of coatings must be carried out according to the basic principles of chromatics. The three primary colors and other polychromes all have the relationship of mutual offset, that is, red, yellow and blue are offset colors, and red and green are a group of offset colors; Yellow and purple are a group of offset colors; Blue and orange are a group of offset colors.

What are the six advantages of the colorimeter:
1. Multi color space color value display
The colorimeter is equipped with a program for converting various color display indicators, which eliminates the need for color measurement personnel to manually convert measurement data, greatly improving the work efficiency.
2. Simple and easy to use Three step color difference measurement
3. PC management system
After the customer purchases, we will give away the color management software free of charge, connect the device to the computer, display the qualification judgment in real time, print the test report, and save the color data of each batch. Color Spectrum Technology has a mature PC management system, which connects the colorimeter to the computer, manages the test data in the upper computer software, exports the instrument data quickly, prints the test report, and facilitates color testers to conduct more complex analysis.
4. Stable measurement performance
standard deviation Δ E * ab 0.08 (after correction, measure the standard deviation of the white board for 30 times at an interval of 10s)
5. Mass data storage
The precision colorimeter can store 100 groups of standard sample data. Each standard sample can store 100 groups of samples.
6. Multiple models and options

LISUN lauched Portable Colorimeter/Chroma Meter is an innovation color measuring tool with powerful configuration to make color measurement easier and more professional; It support Bluetooth to connect with Android and ISO devices, Portable Colorimeter/Chroma Meter will take you into a new world of color management; It can be widely used to measure color value, color difference value and find similar color from color cards for printing industry, paint industry, textile industry, etc.

Lisun Instruments Limited was found by LISUN GROUP in 2003. LISUN quality system has been strictly certified by ISO9001:2015. As a CIE Membership, LISUN products are designed based on CIE, IEC and other international or national standards. All products passed CE certificate and authenticated by the third party lab.

Our main products are Goniophotometer, Integrating Sphere, Spectroradiometer, Surge Generator, ESD Simulator Guns, EMI Receiver, EMC Test Equipment, Electrical Safety Tester, Environmental Chamber, Temperature Chamber, Climate Chamber, Thermal Chamber, Salt Spray Test, Dust Test Chamber, Waterproof Test, RoHS Test (EDXRF), Glow Wire Test and Needle Flame Test.

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