Color detection technology and color management applications
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Color has a very important position in the history of human civilization, and how to apply color and express color correctly and properly is the most important issue, and it is also the goal pursued by mankind. It also has its importance in today's and tomorrow's technological civilization. For example, today's information dissemination technology is constantly improving and changing with each passing day. It is more perfect and true color reproduction for the transmission and expression of color, that is, WYSI-WYG (What You See Is? What You Get’). To achieve this goal, you must have an ideal color vision model that is fully consistent with the perception of the human eye. This ideal color vision mode contains the correct color-difference formula and chromatic-adaptation model, and the ideal color appearance pattern (colour-appearance). Model) and so on. This ideal color vision mode is the basis for qualitative and quantitative applications of various colors.
Human efforts in color technology have so far achieved great success. For example, the National No. Lighting Committee (CIE) has published human eye color function (2° and 10°), CIExyY color system, CIEL*U*V* and CIEL*a*b* uniform colors since 1931. Space, etc., has become a very important content and achievement of CIE colorimetry. CIE colorimetry has also become the basis for the development of color science research in the world today. In addition, there have been great contributions and achievements in technologies such as color detection, computer color matching, computer color separation and color transmission. However, there are still many research and improvement in color detection application technology in the development of the goal of pursuing the ideal color vision mode. For example, the color difference formula is used to predict the derivation of large chromatic aberrations, the evaluation of color variability (Meta- merism), and the deduction of color sample color continuity (Colour Constancy) mode. In particular, color variability and color persistence often cause significant problems for industrial applications or for life and art. It can be seen that color variability and color constancy have an absolute impact on the effectiveness of color detection technology. Therefore, the development and results of the qualitative and quantitative detection techniques of these two color characteristics are the focus of this report.
Color variation can also be called metachromatography, conditional color or conditional color, etc., or simply defined as: two-color stimulus has the same color appearance under a reference light source (generally analog simulated sunlight, D65) (ie The so-called color (but the color), but under a certain second light source (such as tungsten light, A), the two have different color appearance (so-called non-color). This phenomenon is called color variation, and this two-color stimulus is called a color change pair (Metamer).
In terms of application, color variation is often a problem for color-related industries (such as printing, textile, ink, plastic, color TV, lighting, architecture, art, etc.), and even rejected. The collection and compensation will increase the serious loss of production costs. Therefore, the evaluation of color variability is an important part of color detection technology.
In terms of color variability color detection technology, it can be divided into qualitative method and quantitative method. The commonly used qualitative method is (1) visual method: by means of multi-light source standard for color light, observe the color or color difference of the color sample pair under different standard light sources. (2) Reflectance curve method: The color variability is determined according to the intersection number of the object's color reflectance curve (for a transparent object according to its transmittance curve), that is, the more the number of intersection points, the smaller the color variability. However, there are at least three intersections, that is, the greater the variability of the color change, the more the intersection of the reflectance curves will be concentrated at the three intersections. These three intersections are 450 nm, 540 nm, and 610 nm, also known as Barocentric wavelengths. For the quantitative method, CIEL*a*b* (CIEL*u*v* for color light sources), CMC(ι:c), CIE94 and BFD(ι:c) are commonly used for object color. The formula calculates the color difference exhibited by the color sample under different light sources to evaluate the color variability of the color sample pair. In addition, for lighting, CIE color rendering index (CIE) can be used. Colour rendering index) to assess the color rendering of an illuminated or artificial light source. In this report, we focus on the color of objects and explore the advantages and disadvantages of various color variability detection methods.
Color constancy can also be referred to as homochromatic or color constancy. Its relative characteristics are non-color constant (colour Non-constancy), that is, the same color. Both color and color variability are two sides of one body, and they are easily confused. The simple distinction is that color variability is for single color stimuli, while color variability is for two color stimuli. In other words, if a certain color stimulus has the same color appearance under a certain reference light source and under other light sources, the color stimulus is said to have color constancy. In daily life, everyone with normal color vision will have the same experience that most natural objects have a constant color appearance under different natural light. This phenomenon is color constancy. However, due to the advancement of human science and technology civilization, artificial color materials or inks and light sources or lightings are constantly changing and increasing in variety, which greatly improves the non-constantness of objects in daily life and the surrounding environment. Therefore, how to effectively manage color applications has become an extremely important issue today.
The detection technique of color constancy uses the chromatic adaptation model to predict the color appearance of any color stimulus under different light sources or illuminations, and even different media, and then evaluate its color constancy. In application, the color adaptation mode can be used to predict the color saturation of the color stimuli produced by the ink or the dye in a single or mixed use, thereby making the color quality of the product stable or easy to control and manage. Currently, published color adaptation models are like von Kries, Bartl-eson, BFD, CIE (Nay-atani et al.), Hunt, CIEL*a*b*, RLAB, and forthcoming models LLAB, KL95, Kuo96 and so on.