Analyzing the Relationship between color difference and colorimeter

The colorimeter is a color deviation testing instrument, which can automatically compare the color difference between the sample plate and the tested object. That is, to make a filter that simulates the light splitting characteristics equivalent to the color sensitivity of the human eye, and use it to measure the light of the sample plate, the key is to design the light splitting sensitivity characteristics of this type of photoreceptor, and be able to measure and display excellent difference values through computer software under a certain light source. According to the principle of Lab and Lch in CIE color space, it can measure and display the color difference △ E and △ Lab values of the sample and the tested sample, and distinguish the subtle differences between colors to achieve the degree of coincidence between colors.

Chromatic aberration is a serious defect of lens imaging. Color difference is simply the difference between colors. When polychromatic light is the light source, monochromatic light does not produce color difference. The wavelength range of visible light is about 400 to 700 nm, and the light of different wavelengths has different colors. The refractive index is also different when passing through the lens. Color difference generally includes position color difference and magnification color difference. The position chromatic aberration makes the image have color spots or halos when observed at any position, making the image blurred. The magnification chromatic aberration causes the image to have a colored edge. One of the main functions of the optical system is achromatic.

Causes of color difference:
1. Light of various wavelengths will be dispersive to varying degrees. When white light is dispersed into various wavelengths of ultraviolet, visible and infrared wavebands, the image formed when passing through the lens will have a color edge, which is called chromatic aberration. The difference between the actual imaging and the ideal imaging of an optical system is collectively referred to as aberration. Chromatic aberration is one of the aberrations, which is caused by the different transmissivity of the transmission material with different wavelengths, so it can only appear for polychromatic light.

2. Quantitative color perception difference. It is represented by the difference of the three color attributes: lightness, hue and chroma. The difference in lightness indicates the difference in depth, the difference in hue indicates the difference in hue (i.e., red or blue), and the difference in chroma indicates the difference in brightness. The evaluation of color difference is very important in industry and commerce, which is mainly used for color matching in production and color quality control of products. The modern color difference evaluation is based on the standard color difference formula recommended by the International Illumination Association (CIE), measured and calculated with a color difference meter and a computer, and expressed with accurate figures. Such as CIE 1976L * a * b * and CIE 1976L * u * v * color difference formula.

3. Color difference refers to the phenomenon that the products dyed with the same color have different colors between batches, and the products dyed at the same time have several color differences. It can refer to the color difference between different parts of the same product, the color difference between the same batch of processed products, and the color difference between different batches of products originally dyed with the same color.

In the industry, product colors are required to be consistent. Due to the above reasons, there will be deviation in product color, which will reduce the quality of the product. In serious cases, it will lead to failure in acceptance and delivery. At this time, we need to use color measuring instruments such as color difference meter to control the color difference of products.

Control method I: control the product quality of the factory
To ensure the color consistency of each batch of products, a product color standard should be formulated as the factory standard. A certain amount of samples can be taken from different batches of the same product (hereinafter referred to as Product A) for measurement. After measurement, select the products with relatively large color difference, and take the products with relatively similar residual color difference as the calibration samples of product A. Measure the color value of the calibration sample with a color difference meter in turn, and calculate the average value (the instrument can automatically calculate the average value). The average value shall be used as the color factory mark of product A and stored in the colorimeter. The storage sample number can be set to 001 for easy memory. If there are multiple products, the factory marks can be measured in sequence according to the above method, and stored as 002, 003, etc.

In the future production process, to check whether the color of product A is qualified, you can call out the standard sample value (data 001) of product A from the color difference meter storage, and then locate the standard value. Take samples from each batch of product A for measurement, and the measured color difference value is the result of comparison with the factory standard. Color difference value of product（ Δ E) Now most manufacturers control it within 0.5 or 1, that is, color difference（ Δ E) If the color difference is less than 0.5 or 1, the product is regarded as unqualified. If the color difference is more than 0.5 or more than 1, the product is regarded as unqualified. For other products, the corresponding product manufacturer’s standard is called out in this way, and then the standard value is determined for measurement and analysis.

Control method II: production according to standard samples
Many companies order products according to the samples provided by the ordering company. They can measure the samples provided by the other party with a colorimeter, store the measurement results in the instrument, and remember the stored sample number as a standard sample. During application, call out the value of this standard sample and set it as the measurement standard value, then measure the products produced in turn, inspect the product color difference value according to the steps of “Method 1”, and evaluate whether the product color is qualified.

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.

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