A brief introduction to the production principle of raster stereo printing

In recent years, with product packaging and filling, it has become richer and more beautiful. A brand new product quietly appeared in people's daily life. Have you paid attention to the cute little cards in the food package? 7 Tilt the card or move the card back and forth to see all kinds of wonderful effects.

This is the product made by the technology of grating stereo printing. It is widely used in packaging and acting products, commercial advertisements, science and education cartoons, postcards, New Year's cards, anti-counterfeiting marks, trademark tag mouse holders, various types of credit cards, etc. It is also used to decorate and fill various products. The printed pattern is continuous, without seams, and has excellent authenticity. Simultaneous multi-angle stereo printing can be performed on irregular surfaces of shaped objects. Now it can also imitate all kinds of natural patterns such as precious wood, jade, agate, snakeskin, marble, etc., and it is difficult to distinguish true and false together with the natural materials to achieve an excellent simulation effect.

Raster three-dimensional printing is the printing that uses a kind of grating plate to make the image have a three-dimensional effect. This kind of printed matter can directly observe the three-dimensional stereoscopic image on the two-dimensional plane image without any tools. Looking at these products, people must be curious how it is made? People can naturally produce a three-dimensional sense when observing objects, because there is a certain distance between human eyes. When observing an object, the left and right eyes observe from different angles to form a visual difference between the two eyes. The various images formed are reflected in the brain, which produces a sense of distance and three-dimensionality.

Prepress production uses this principle to achieve stereo imaging using cylindrical lens stereo gratings. That is, it uses the binocular parallax and convergence of human eyes to form a sense of depth to realize the three-dimensional sense in human consciousness. Therefore, in theory, only a group of images obtained from more than two different observation points can synthesize a stereo picture.

Cylindrical lens stereo grating is composed of many small cylindrical cylindrical lenses with the same structural parameters and performance. This feature makes it have "compression" and "isolation" effect on the image. The cylindrical stereo grating can record many images taken from different angles on the same picture in the state of stripes. When viewing, the same kind of cylindrical stereo grating is also used to make two eyes see two different images of the same scene, so a deep image with parallax stereo effect is produced in the human mind. The cylindrical lens stereo grating is composed of cylindrical lenses arranged linearly in a plane. Therefore, the stereoscopic image of the cylindrical lens stereoscopic grating should be called a unidirectional autostereoscopic image. Its significance is that only horizontal parallax information can be felt.

According to the principle of cylindrical lens stereo grating imaging, the stereo pictures produced by optical methods mainly have the following characteristics:

1. The three-dimensional picture must be a group of pictures taken from different angles of view of the same scene. Due to the unidirectional stereoscopic nature of the grating, the position of this group of pictures is required to be at the same height.

2. The synthesized three-dimensional picture is composed of stripes parallel to the axis of the columnar grating. The corresponding bit information of each picture in a group of pictures is arranged in sequence at equal intervals under the same grating pitch. As shown in Figure! Shows the situation of a three-dimensional picture synthesized by two pictures. 3 Due to the shooting position of each picture. The same point has two corresponding points on the three-dimensional picture, so that the position is shifted. This is why the three-dimensional sense is formed.

The biggest challenge facing raster stereo printing is color separation and plate making because the stereoscopic effect of the raster is obtained by separating and reorganizing the image into a fine raster. The key is to process the image by the interlaced scanning software. This kind of file data is generally relatively large, requiring the computer to have sufficient processing power to process the scanned image file. In addition, the fine pixel characteristics of the stereoscopic image and the magnifying effect of the lenticular grating make the plate-making screen counting device more than 120 lines / cm.

Since the three-dimensional picture image is composed of closely arranged pixels, and after the plate making and printing, a composite cylindrical mirror plate is also needed, so when selecting the screen angle, it is necessary to consider not to form moire between the screens. Also pay attention to each net The moire formed by the angle of the screen and the pixel lines and lenticular lines. It is not suitable to select the angle of the screen line in the three-dimensional printing. Because the horizontal network cable is the most obvious, and. 'It is orthogonal to the pixel line and the cylinder line, which interferes with the clarity and depth of the image. Because the three-dimensional printing uses a very fine 300-line screen. When printing, only 8.5% or 90% of the exposure is used. Otherwise, the printing is easy to paste. In this way, the amount of color in the dark area needs to be increased to reach 9. -9.5 into a point effect. Therefore, the solid density of three-dimensional printing is higher than that of flat four-color printing.

The requirements for three-dimensional grating printing are very accurate. At present, there are two main printing methods. One is to print directly on the grating material, and the other is to print on the paper and then paste it on the grating or on the plastic film and then press out the grating. . The grating thickness is between 0.008-0.385 inches. Therefore, if the printing overprint is not accurate, even if it is a very small deviation, the printed product will become a scrap. A very small gap will affect the effect of the entire layout. Therefore, the raster three-dimensional printing requires high precision for printing equipment, and the overprint error should be less 0.0lmm.

In the case of a cylindrical grating plate and a printed product, a combined printing process. The process of accurately bonding the image and the grating plate together is very critical. Some enterprises operate manually. There are many uncontrollable links, and the operation skills of workers directly affect the quality of stereo pictures. The method of sticking the grating board to the synthetic type is to coat a layer of bright glue on the printed finished product and heat and dissolve the thermoplastic material with high transparency in the mold to form a cylindrical grating board. The board is attached to the printed finished product The precise alignment of the grating lines and the grating lines on the printed matter can show the three-dimensional effect. The lenticular pitch is 0.6mm, and the uneven surface formed divides the image into countless pixels at equal distances. There are about 48 concave and convex lines per centimeter of cylindrical grating plate. There are about 6 pixels under each concave and convex line. It is difficult to control the precise alignment of the grating lines and the grating lines on the printed matter. The printing process directly printed on the grating material is relatively easy, as long as the machine precision is achieved, the finished product can be printed directly. But unlike traditional printing, it is necessary to coat a layer of white varnish on the printing surface.

Although the theory of three-dimensional photography stable image suggests that the master has less than 100 years of history, the practical application of this technology has developed very long. Raster stereo printing is derived from the three-dimensional stereoscopic film provided by stereo photography. However, due to the use of traditional optical principles in the production and synthesis of stereoscopic photographs, the application and application of stereoscopic photographs have great limitations, high requirements for equipment accuracy, and complicated process technology. The production cost is high. Therefore, three-dimensional photography has not been promoted and popularized, and at the same time, three-dimensional printing is subject to a large cumulative error between long processes in the pre-press production process. The screen resolution is low and the printing effect is not ideal. Difficult operation, low efficiency, poor quality, high scrap rate, and expensive expensive special manufacturing equipment and consumables are also reasons that greatly hinder the application and development of grating stereoscopic printing technology.

In the 21st century, three-dimensional photography has entered the digital age. People use computer software for multi-image synthesis. The rapid development of computer technology, especially image input, processing and output technology, provides convenience for computer synthesis of stereoscopic pictures.

With the advent of computer-to-plate CTP technology, high-precision printing with FM dots is used. The application of UV technology continues to mature, and many equipment manufacturers have launched various types of UV offset printing machines. Heidelberg, Manroland, KBA, Komori, Ryobi, etc. have all launched offset presses with this feature. Direct printing of plastic grating materials with offset presses is no longer a problem. The quality system for stereo printing is guaranteed. This has led to the rapid development of grating stereo printing. In recent years, domestic three-dimensional printing has been greatly developed. The printing factory began to use the grating three-dimensional printing process to obtain more complex products. From labels, posters to packaging products, and even plastic cups, three-dimensional printing has been applied to present a thriving scene.

Although what is seen in the product is not a stereoscopic effect in the true sense, but the raster stereo printing is not just a trick to entice children. Compared with the traditional three-dimensional photo production process. It shows its unique advantages in terms of economy and flexibility of use. We have reason to believe that the raster three-dimensional printing technology will have a wider application space and development in the future printing field. prospect.

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