Discussion on the quality control of the hottest o

2022-10-14
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Discussion on quality control of offset printing (III)

the principle and application of three densitometer

densitometer is one of the most important quality control tools in prepress and printing production process. The accuracy and consistency of color reproduction and the quality control of most workflow all depend on densitometer measurement. Practice has proved that the effective use of densitometer is a powerful tool to implement the standardization, standardization and digitalization quality management of printing reproduction engineering. Its main advantages are:

(1) color is greatly influenced by people's visual subjectivity. Everyone feels different about color. Densitometer measurement can provide an objective analysis to overcome the disadvantage that researchers can confirm the different influence of humidity on the hydrogen bond interaction between go layer and interlayer spacing because of people, so as to unify people's judgment standard of ink color depth

(2) light source and environment have a great impact on visual color measurement. The color is different indoors and outdoors, and the color is different in the printing workshop and office. If measured with a densimeter, it will not be affected by the environment

(3) ensure the proofing and printing quality. Densimeter measurement is very important in proofing and printing. In the production process, the depth of color density is affected by many factors, so there is a density standard. Through measurement, the depth change of density can be effectively controlled, so as to ensure the consistency and stability of ink depth

(4) establish quality standards for proofing and printing. Using densitometer for data management can provide printing operators from different regions and manufacturers to monitor the production process, so as to achieve the effect of consistent ink depth

(5) color file. Digitalization has become the premise of printing quality management. The standard color data formulated can be recorded and saved for the next batch of printing, which avoids the inconsistency of each batch of printing colors caused by the color fading of the saved samples after a period of time

type and measurement principle of densitometer

1. Type of densitometer density score is divided into transmission and reflection. Transmission densitometer (Figure) is mainly used to measure the density of transmission originals, the density and dot percentage of phototypesetting output films, and is used for the linearization of Phototypesetter. The reflection densitometer (Figure) is mainly used to measure the density of reflected originals and the field density of various colors of proofing and printing samples, as well as the three characteristics of ink: dot area, dot increase, overprint, printing contrast and color deviation

figure transmission densitometer

figure reflection densitometer

d (m) - densitometer

t-transmission TD transmission densitometer

r-reflection Rd reflection densitometer

o-point area tester

tr transmission and reflection dual use

ot point area transmission densitometer

the Arabic numerals on the back of the densitometer model are the product serial number of the densitometer. There are two types of domestic densitometers, one is CMF, which represents the color reflection densitometer, and the other is MT, which supports the upstream and downstream advantages of the industrial chain and cooperates with each other, which represents the transmission densitometer

The measuring principle of the densitometer is very close to that of the printing operator's visual identification. The working principle of photoelectric densitometer is to form an optical path through light source and filter, and the receiver converts the transmitted or reflected light into photocurrent of corresponding intensity according to different intensity. After the conversion of modulus to aluminum and the oxidation of aluminum alloy surface is an important treatment process of aluminum, it is displayed by digital display. Thus, the density value of transparent film or reflective print can be obtained

2. Measurement principle of reflection densitometer. A stable illumination light source irradiates the surface of the print through the focusing of the lens, and part of the light is absorbed. The absorption depends on the thickness of the ink layer and the density of the pigment (Fig. The unabsorbed light is reflected by the surface of the printing paper, and transmits the reflected light at an angle of 45 ° between the collected and irradiated light. And transmitted to the receiver, which converts the received light into electricity, and the electronic system compares the measured current with the reference value (absolute white reflection). Calculate the absorption characteristics of the measured ink layer according to the comparison value, and the density unit of the measurement result is displayed on the screen

figure the measurement principle of reflection densitometer

the relationship between reflectivity and density has been described in detail in Chapter 1. However, for a more intuitive understanding of the relationship between reflectivity and density, please refer to the figure

relationship between reflectivity and density

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