FM screening technology

The emergence of Frequency Modulated Halftone Dots (referred to as FM network points) and its advantages in image resolution, non-rhizome, and articulation and other aspects have received widespread attention from the printing industry. With the improvement of materials and supporting technologies, it will become a major screening method superior to conventional amplitude modulated dots (AM). The conventional screening technology uses the method of changing the dot size to reproduce the color and gradation changes of the continuous tone manuscript. The size of the dot change corresponds to the amplitude modulation in the radio technology. For this reason, the conventional screening technology will be used after the frequency modulation screening technology emerges. The network generated by technology is called amplitude modulation network point.

The difference between the FM network technology and the AM network technology lies in that it does not change the size of the network dots, but the computer generates the same size points from the pixel values ​​of the digital images. The minimum diameter of these points can be equal to the recording accuracy of the equipment. A set of finite point groups in a halftoning unit constitutes a very special form of dot, it has no fixed shape, and the positions of these dots appear to be random and are also called

"Random dots," for example, two pixels that are exactly the same in numerical value when using FM screening technology to form dots, although the number of recording points is the same, but the location is different. The sum of the areas that make up an FM recording point is equal to the size of a regular cell, and its area ratio is also equal to that of a regular cell. AM sites are the effect of the tonality of the image by the size of the site. The frequencies of the sites in the space and the number of Internet sites per unit area are constant, and the tone of the image is expressed by changing the area of ​​the network. That is, the site of the bright tuning site is small and dark The network is large; the area of ​​the FM network is fixed, and the distribution density of the network in the space is changed.

(Denseness) to represent the image tone.

There are many advantages of FM network sites compared with AM sites, which are mainly manifested in:

1) Eliminate the occurrence of "rhizard". Color printing is usually accomplished by accurately overprinting four separate screen images. These images are printed using four inks of cyan, magenta, yellow, and black respectively. They use AM screening technology, regular ordered dots and dots. Simplification, will inevitably produce network line angle, inevitably produce "rhizome" in the process of overprinting. With the frequency modulation screening technology, the probability of appearance of network points is random, the arrangement of network points is irregular, and there is no regular spatial network structure, eliminating the interference caused by certain regular stripes of the image itself and the screening screen. The possibility of "mopy".

2) Improve color reproduction capabilities. Due to the irregular distribution of FM network points, there is no network line angle problem. Therefore, colors other than cyan, magenta, yellow, and black can be used to expand the color gamut, increase spot color ink printing, and achieve high fidelity (HiFi) color printing. The color difference between the original and the original is reduced, and the color reproduction ability is improved. This is extremely helpful for the printing business market to increase profits. In addition, due to the irregular distribution of FM network points, overlapping dots can be avoided, and the ink can be directly printed on the substrate. Therefore, a larger ink volume can be used to increase the color effect.

3) High resolution. FM network technology is the density of networks, that is, the number of network points per unit length (DPL) represents the fineness of network images, and the blackening points that make up the FM network points are the “elements” that form the image hue, and are also the most subtle Basic unit. With the same resolution of the system, the FM network point has a higher resolution and higher resolution than the AM network point. In the AM screening technology, the resolution of the dot line determines the sharpness. The higher the number of lines, the smaller the dot area of ​​the output and the better the sharpness. However, usually the number of network lines is too large, and the copying technology is more difficult. Therefore, the output images generated by the amplitude modulation screening technology have to be emphasized at the subtle level, namely USM. Because the screen area used by FM screening is particularly small and the image reproduction is of high definition, the copying effect is close to that of continuously adjusted photographs, especially the subtle levels of highlights and shadows are well reproduced. The adoption of the FM network point technology in the low-resolution imagesetter can also obtain high-quality images, while the amplitude modulation dot-screen technology requires a relatively high resolution.