A Survey of Print Reproduction and Technology Research (2)

1.2.1 Development of graphic imposition processing technology

The development of graphic and text imposition technology can be divided into three categories: one is the color electronic whole-page imposition system, the second is the simple imposition system, and the third is the color desktop publishing system (hereinafter referred to as DTP). The former two are based on the electronic color separation machine and are mainly used to process images. They generally have vivid color display, higher computer operation speed and processing capability. The simple imposition system refers to having general imposition functions, such as masking and revision functions, while the functions of level correction, color correction, pixel editing, etc., need to be relatively complete in high-end systems. In color prepress, electrical extensions and color full-page imposition systems have always dominated, but they are powerless in mixing text and color images. With the popularity of color printing, the demand for printed materials is getting higher and higher. This requires a full-color imposition system to meet the development needs, and the advantages of DTP will be revealed.

Since the mid-1980s, electronic color separation machines and full-page imposition systems have gradually become the main plate-making equipment for color image reproduction in China. The electronic color separation technology has also become increasingly mature. From 1987 to 1991, it was basically the promotion and application period of black-and-white laser phototypesetting systems. In the 1990s, China developed a color desktop publishing system successfully developed by the Peking University Computer Research Institute and reached the international advanced level, setting off a color revolution in the world. The color revolution began with the newspaper industry: it began trials in the Liberation Daily in 1991. On January 21, 1992, the Founder Color Print System at Peking University was put into production and use in the “Macau Daily”, and 4 to 6 editions of color newspapers were published every day. Become the first Chinese newspaper in the world. From that day onwards, the “Macau Daily” completely ridded the traditional extensions, entered color photos with a color scanner, and completed the text-in-one processing within the system. The RIP hooked up the color photos and then output the entire page. The quality is not lower than the electric extension.

The term DTP (Desk-top Publishing) appeared in 1985. It is essentially a full-page imposition system that integrates text and images on a personal computer. In July 1985, Apple Computer Inc. consisted of a Macintosh personal computer with Adobe's Pagemaker, a full-page imposition software, and a laser printer adapted to Adobe's Postscript language. Israel's Scitex company developed the world's first color desktop publishing system in 1988. It is based on Apple's Macintosh II high-end personal computer. Coupled with the maturity and application of technologies such as digital information technology, compressed information technology, page description language, raster image processing technology, and computer communication networking, the electronic platemaking system has become smaller, more individual, and more versatile. At the same time, it has the advantages of being able to add, combine, and network. This has led to the rapid development of the color DTP system and integrated text processing system.

Since the desktop publishing software has a Chinese character processing function and the establishment of a Chinese character PS library, China has the technical conditions for applying a desktop publishing system. After 1994, desktop publishing technology was first promoted in China's advertising production and design fields. Due to the computerization of prepress editing, since the 1990s, desktop publishing technology has become increasingly mature and widely used in newspapers, books and magazines, and packaging and printing.

1.2.2 Progress of Screening Technology

Before the appearance of the color prepress system, all screening methods can be summarized as AM screening (abbreviated as AM screening). The distance between networks in the AM network is fixed and fixed. That is, the frequencies of the networks are fixed and change only the size of the network, that is, the size of the network is different. Therefore, this type of screening is called AM screening. .

In the AM screening method, the electronic screen used by the electronic color separation machine is the IS network point technology (irrational tangent network point) and the RT network point technology (rational tangent network point) developed by the German Hell Company. The Postscript screening technology is used in the color desktop publishing system.

Because of the disadvantages of moiré and rose spots and gradation leap in the amplitude modulation screening (that is, layer jumps occur before and after the mesh starts to overlap), it is difficult to improve the printing quality, and it is difficult to develop the four-color printing mode. Since the 1990s, new screening technologies have emerged, namely FM screening technology. FM network, also known as random network, was formally launched at the International Printing Technology Exhibition in 1996. This kind of screening method has the same network size, uses the degree of density of the network to represent the image hierarchy, and the network distribution is random, so this screening method is called FM screening. It is characterized by the absence of web corners, so that no moiré and rose spots are formed. FM screening technology has been considered as a better screening method through practice, and its quality is higher than that of AM screening.

FM network technology currently has some shortcomings. In the printing, the dot enlargement of the network at the time of printing is 10% larger than that of the AM. Because the dot is small and the dot is easy to lose, the quality of the printing plate is required to be high. However, with the application of computer-to-plate technology, FM screening technology will be better applied because it eliminates the printing process.

At present, there are also network technologies that integrate FM and AM. In 2000, Dainippon Screen Company developed a brand new hybrid screening technology for the first time in the history of printing technology development. It can choose "Modulation Plus" and "Frequency Screen Plus" in due course according to the change of screen color and level. With the in-depth application, the research of screening technology will produce new results.

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