The hottest new trend of modern screening technolo

2022-09-22
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As we all know, the traditional addition method refers to amplitude modulation (AM) addition. However, amplitude modulation plus method is easy to produce "moires", so people hope to find an effective way to avoid "moires". Therefore, frequency modulation (FM) plus mode came into being. Color printing reproduction is C (green) m (product) y (yellow) K (black) four-color printing. CMYK four-color ink printing with a specific angle will produce a color "rose pattern". Moreover, the color "moire" is very obvious in a continuous angle range, which destroys the effect of the image itself. The application of traditional adding method often produces "moire". Why does it produce "moire"? There are two reasons. First, if the angle between the color and the color is not appropriate, or the overprint is not accurate when printing, it will produce "moire". Second, sometimes the pattern in a specific background has visual conflict with the screen line used for printing, which will also produce "moire". For example, when printing textile patterns, the "longitude and latitude" lines in the textile patterns will interfere with the printing screen and affect each other to produce "moire"

frequency modulation plus (or random plus), refers to the constant size of the pointer (generally much smaller than the traditional halftone amplitude modulation plus) to reproduce the order and level of the image by changing the occurrence frequency of points per unit area. When the points converge, a dark area of the image is formed. When the points are sparsely distributed, the bright region of the image is formed. Because FM plus does not add line number and angle, there is no "moire" in color image printing and reproduction. The result fundamentally solves the problem that the traditional addition method (amplitude modulation addition method) is easy to form "moire". Advantages of FM plus: at first, FM plus was mainly used in printing high-quality and fine prints, such as art albums. Because FM reproduces the details of fiber and jewelry clearly without "moire". With the popularization of FM plus in printing production, it is found that FM plus can effectively enhance the printing effect of low resolution images. The detail reproduction effect of its low resolution image plus output draft can be comparable to the printing effect of amplitude modulation plus output draft with high number of lines, so the lower resolution image can be used for prepress typesetting. Because there is no angle, FM plus is insensitive to inaccurate overprint. Thus, the adjustment time of printing registration and the preparation time of machine adjustment are saved, the scrap rate of machine adjustment is reduced, and the production efficiency of printing enterprises is improved

disadvantages of FM plus: Although FM plus has many advantages in printing production, FM plus is not perfect. In the traditional Phototypesetter printing production process, printers spend a lot of time to ensure the consistency of film to plate point transfer. FM plus, like am plus, is also very sensitive to the instability of chemical development process in the printing process. The graininess of printing in low contrast, flat and high light areas is very obvious, and the dot enlargement is also serious, and the printing plate densitometer cannot measure the reliable optical density of frequency modulation. In order to obtain the ideal printing effect, it is necessary to use the dot enlargement compensation curve to correct the output equipment; Or printing with waterless offset printing process, because waterless offset printing can effectively reduce point expansion

the development trend of modern printing plus technology. Modern printing plus technology is in the ascendant, new adding algorithms emerge in endlessly, and traditional adding methods are also constantly developing and improving. However, the addition methods can be divided into three categories: the new addition algorithm based on secondary frequency modulation addition, the new high-definition addition algorithm based on amplitude modulation addition and hybridscreening (hybrid addition algorithm)

1. A new addition algorithm based on secondary frequency modulation addition

secondary frequency modulation addition so that the car can stop safely is generally divided into two steps. For the first time, it mainly determines the position of points and uses point aggregation to generate image dark areas; For the second addition, an effective algorithm is applied to generate smooth and orderly image middle and bright areas, and the size and shape of the points are adjusted to control the noise and color difference after the added image rotates the clamping device by a certain angle. The advantages of secondary frequency modulation are smooth tone transition, low image noise and dot spread. However, it is still difficult to adjust the color in printing

2. The development of a new high-definition addition algorithm based on am addition

FM addition technology enables people to obtain a moire free and clear detail printing effect. But now, some printing equipment suppliers have developed many new processing technologies based on traditional am processing technology by combining the advantages of am processing and FM processing. These new processing technologies innovatively use high-definition am processing technology, so that low-resolution output documents can generate much higher number of lines than general output through this algorithm. For example, a 360lpi wired digital screen can generate 2400dpi resolution output through this addition method. In addition, the matching points expand the correction output of the compensation curve, and very small points can also be retained and printed on the printing plate. Therefore, this addition technology can make the printing machine easily print very good image details, and the operation is simpler, while avoiding the defect that FM addition cannot adjust the color in printing

so how can it avoid the appearance of "moire"? This new addition technology based on am addition provides more flexible addition angle settings. In addition to several standard offset addition angle settings, it also provides two new addition angle settings, 30o and 60o. In this way, this new high-definition addition algorithm based on am addition can not only obtain better detail effect than FM addition, but also maintain the same process stability and color adjustment flexibility as am addition

bridscreening (hybrid addition algorithm)

recently, there has been a hybrid addition method, which includes both FM addition and am addition, but it is different from the traditional FM addition and am addition

in actual production, printers can use it flexibly according to their needs. Sometimes, we can use FM plus for the green version, magenta version and black version, and use the traditional am plus for the yellow version. Or in the same color version, different contents (such as images with different resolutions) are mixed with two addition methods. For example, in order to improve the printability, FM plus is used for the highlight area of the image, and am plus is used for the middle tone. This is because in the middle tone, the point spread size generated by am plus is clear. However, in the high light area, the dot is very small, which is more suitable for FM plus printing. This mixed addition method is very suitable for flexographic printing process and offset printing process. There is also a technology called high-density processing, which has also been applied to flexographic printing. We know that the general field density of flexo printing is not high enough, and a few laboratories adopt semiconductor refrigeration tank, and this technology can help flexo printing produce higher field density than the general addition method. It actually uses thin lines to replace the dots in the dark tone area, which can improve the printing reproduction effect of the real area and improve the thickness of the printing ink layer and the saturation of the color

when we develop from electronic extension to DTP (color desktop publishing system) and now the popular CTP direct plate making system, the addition methods are gradually diversified. However, whether based on am plus or FM plus, the new plus technology has improved the detail reproduction ability of the image to varying degrees. With the update of the addition algorithm and the improvement of the printability, we believe that in the near future, we will see a new generation of addition algorithm with the advantages of clear, no moire, good printability and more bright colors, such as wide measurement range, high accuracy, compact structure, convenient operation and stable performance

source: Guangdong Printing

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