Printability of the hottest FM DOT 4

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The printability of FM dot

1. Introduction

in the process of image reproduction, the traditional addition method is used to express the intensity level of the image. After more than a century of unremitting efforts, printing technicians have made considerable achievements in promoting the production and utilization of bio based plastic products. However, due to this addition method, there will be many regular rose shaped stripes during color overprint, and sometimes even moire. At the same time, due to the decomposition of points, with the reduction of the number of lines, the sharpness of the image decreases sharply, losing the characteristics of the original. In recent years, with the research of high fidelity reproduction technology, ultra-fine dot printing of more than 120l/cm has emerged, which can accurately obtain the image effect of fine level reproduction and continuous tone. However, no matter how fine it is, the characteristics of its points are that there are regular distribution of positive or negative points of different sizes in the image part, and there is always its fatal weakness. The structure of rose flower type, that is, the pattern phenomenon caused by adding angle, is independent of the number of lines. At the same time, if the number of lines exceeds a certain limit, it will not only bring greater difficulties to replication, but also cause more serious loss of step value, especially the highlight part, and there are certain restrictions on the resolution, which is the biggest drawback of the traditional addition method

2. Characteristics of frequency modulation points

in the 1970s, foreign countries began to study a frequency modulation addition method. It is different from the traditional addition. The printing points are calculated based on the statistics of the hue and hierarchy of adjacent parts in the image. They are irregularly randomly distributed in the image area and have the same size (most of them are μ m) , use the far 3-axis and vibrating table to show the intensity level of the image. Because the technical conditions at that time could not meet a large number of computing needs, it was postponed to the 1980s. With the development of electronic computers and the substantial improvement of computing power, this addition method was realized. However, at this stage, FM addition is only a random addition of a first-order function, with equal point sizes, and the change of point spacing is different from that of the photo image by halogen particles of different sizes and distances (0 μ m) Deposition to form tones or colors is still different. Therefore, people continue to study. Ganfeng international and mtmarion signed a long-term underwriting agreement. If the second order function is used to add randomly, the distance and area of the dots can change randomly. Then, the second order function addition is very similar to the original photo in terms of the mechanism of expressing the tone, and the replica will be more realistic, which is completely close to the effect of the photo image. Of course, the calculation of random addition of second-order functions is larger and more complex, but it is believed that it can be realized in the near future

in fact, at this stage, people have shown incomparable advantages over the traditional addition method by using first-order function frequency modulation addition. In order to show that using computer algorithm to control the dot arrangement can actually eliminate the unsightly pattern like periodic structure, which is more suitable for image reproduction above three primary colors. Due to the fine frequency modulation and dot adding, if the diameter is 15 μ The idea of M can undoubtedly reproduce 1%-99% of the tone value, so the replica has high resolution, soft image tone, rich layers, realistic images, and whether there is moire effect. This is the charm of FM plus method that can be affirmed by printing experts

3. Minimum point size of engraving

in FM plus technology, the only key parameter is the size of the point, which is much less than the traditional art printing parameters. It does not have the problems of point angle, line number and point shape. The size of the frequency modulation point is only related to the recording accuracy of the exposure device. Theoretically, the size of the light spot recorded by a 1200dpi Phototypesetting is a square spot with a side length of 1/1200in, but in fact, the light spot exposed on the photosensitive film by laser is a circle with an area slightly smaller than this square, about 21 μ m. That is equivalent to 1.2% dots of 60l/cm, or 1.5% square dots

it can be seen from table 1 that with the improvement of recording accuracy, the light spot becomes smaller. Judging from the output accuracy of the current Imagesetter, it is completely guaranteed to produce the FM dot size that meets the printing requirements. The problem depends on the printable dot size in printing. Therefore, FM addition is more about printing technology than computer hardware. Therefore, the minimum printable size is a key factor in printing, but its value varies due to the influence of printing equipment, materials, technology and technical level. It is reported that assuming a certain resolution, taking a light spot as the inking point, foreign countries can print on smooth paper with high quality, and the minimum printing point can reach 8 μ m. It can also be printed on rougher paper μ M points. But in our country, according to the test, it is less than 20 μ M-point printing is quite difficult, obviously there is a big gap

4. FM dot printability

dots go through many process transformations from the generation of negatives to printing to the printing to the crushing of test pieces, and the changes in each transformation directly affect the color restoration of the image, which is the existence of any processing technology. However, due to the different structure, fine dots, and the change law, the frequency modulation plus is different from the traditional plus, and its control conditions may be more strict. Now, according to the actual conditions, it is assumed that the recording accuracy is 1200dpi, that is, the inking point is 20 μ M size to discuss the requirements of FM dot printability

4.1 image density of output film

generally, the laser dots added by frequency modulation are often circular dots with jagged edges. The finer the dots are, the less halogen silver particles are deposited on the negative film, and the lower the density is. According to the requirements of printing standardization, its density must be greater than 2.30. At the same time, there must be no more than two diameters 6 inside the point μ M, otherwise and are unqualified

therefore, the film output by the laser recording device should preferably use the extra hard film matching the device. The output points are required to be solid, dense, transparent and clean. Because the dots are small, it is not allowed to use corrosion methods to eliminate spots or correct dots during film processing, and avoid repeated copies. Therefore, in addition to the strict specification and standard operation of the film washing conditions, it is best to have the supporting treatment solution and dust-proof clean environmental conditions suitable for FM addition

4.2 printing requirements

the basis of the printing point is the sand mesh on the surface of the printing spot. The finer the sand mesh, the more sand mesh on the support point, the stronger the adsorption force, and the smoother the edge of the point, so it is only 20 for one μ For m-Size frequency modulation point, in order to maintain its due printing resistance and not be worn, try to use a printing plate with fine sand grains and high resolution. According to international standards, the average roughness of the ideal sand mesh is 2.5 μ m. Depth 3 μ m

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