The principle and future development of grating stereo printing
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In recent years, as the product is packaged and filled, it has become increasingly rich and beautiful. A brand new product quietly appears in people's daily lives. Have you noticed the cute little card included in the food package? 7 Tilting the card or moving the card back and forth will see all kinds of wonderful effects.
This is the product made by the grating stereo printing technology. It is widely used in packaging and dressing products, commercial advertising, science and education cartoons, postcards, Chinese New Year films, anti-counterfeiting marks, trademark tag mouse support, various credit cards. Also used in the decoration and filling of various products. The printed pattern is continuous, seamless, and has excellent pseudo-authenticity. Multi-angle embossing can be performed simultaneously on the irregular surface of the formed object. Nowadays, it can also imitate various natural patterns such as precious wood, jade, agate, snakeskin, marble, etc., and it is difficult to distinguish the excellent simulation effect with the natural materials.
Raster stereo printing is a printing that uses a grating plate to give a three-dimensional image. This kind of print can directly observe a three-dimensional image on a two-dimensional plane image without any tools. Looking at these products, people must be curious about how it was made.
People can naturally produce a three-dimensional sense when observing an object because there is a certain distance between the eyes of the person. When observing an object, the left and right eyes are observed from different angles to form a visual difference between the two eyes. The various images formed are reflected in the brain, and the sense of distance and three-dimensionality are generated.
Prepress production utilizes the principle of stereoscopic imaging using a cylindrical lens stereo grating. That is, the stereoscopic feeling formed by human binocular parallax and convergence is realized. Therefore, in theory, a stereoscopic picture can be synthesized only by taking a set of images of the scene from two or more different observation points.
The cylindrical lens stereo grating consists of a number of small cylindrical lenses with identical structural parameters and properties. This property gives it a ''compression' and 'isolation' effect on the image. Cylindrical stereo gratings can record many images taken from different angles in the stripe state on the same picture. When viewing, the same kind of cylindrical stereo grating is also used, so that two eyes of the same scene can be seen by both eyes, and then a depth image with a parallax stereo effect is generated. The cylindrical lens stereo grating is composed of a cylindrical lens arranged in a line shape. Therefore, the cylindrical lens stereoscopic stereoscopic picture should be called a one-way autostereoscopic picture. The meaning is that only horizontal parallax information can be perceived.
The stereoscopic picture produced by the optical method according to the cylindrical lens stereoscopic grating imaging principle mainly has the following characteristics:
1. The stereo picture must consist of a set of pictures taken from different perspectives of the same scene. Due to the one-way stereoscopic nature of the grating, the bits at the time of this group of pictures are required to be at the same height.
2. The synthesized stereoscopic picture is composed of stripes parallel to the axial direction of the columnar grating. The same grating pitch is arranged in the corresponding position of each picture in a group of pictures in equal intervals. As shown in the figure! The stereo picture is composed of two pictures. 3Because of the location of each picture, the same point has two points on the stereo picture, so that the positional displacement is formed, which is the reason for the stereoscopic effect.
The biggest challenge faced by raster stereo printing is color separation platemaking because the stereoscopic effect of the grating is obtained by separating and recombining the image into a small raster. The key is that the interlaced software processes the image. This type of file data is generally large, requiring the computer to have enough processing power to process the scanned image file. In addition, the characteristics of the stereoscopic image pixels are fine and the magnification of the lenticular grating is more than 120 lines/cm.
Since the stereoscopic image is composed of a series of closely arranged pixels, after the plate making and printing, the cylindrical mirror plate is also to be combined, so in addition to the formation of the mesh angle, it is necessary to consider not forming a turtle between the screens. The screen angle and the moiré formed by the pixel lines and the cylindrical lines. In the three-dimensional printing, the angle of the cable should not be selected. Because the horizontal network cable is the most obvious, and. 'It is orthogonal to the pixel line and the column line, which interferes with the sharpness and depth of the image. Also, because of the three-dimensional printing, it is a very fine 300-line screen. In the printing process, it only uses 8.5% or 90% of the sun. Otherwise, it is easy to paste when printing. This requires increasing the amount of color in the dark area to reach 9 -9.5 points effect. Therefore, the three-dimensional printing has a higher density in field than the four-color printing.
The three-dimensional printing requirements of the grating are very precise. At present, there are two main printing processes, one is to directly print on the grating material, and the other is to print on the paper and then paste it onto the grating or paste it onto the plastic film and then press the grating. . The grating thickness is between 0.008 and 0.385 inches. Therefore, if the printing overprint is not allowed to be extremely small deviation, the printed product will become a waste. A very small gap will affect the effect of the entire layout. Therefore, the three-dimensional printing of the grating has high precision on the printing equipment, and the overprinting error should be less than 0.0l mm.
In the case of a post-synthesis printing process for cylindrical grating plates and printed matter, the process of accurately attaching the image to the grating plate is critical. Some companies are manual operations. There are many uncontrollable links, and the worker's operational skills directly affect the quality of the stereo picture. The method of splicing the grating plate is to apply a layer of bright glue on the printed product, and heat and dissolve the highly transparent thermoplastic material into a cylindrical grating plate in the mold. The plate is attached to the printed product. The raster line is precisely aligned with the raster line on the print to show a three-dimensional effect. The lenticular pitch is 0.6 mm, and the resulting concave and convex surface divides the image equidistantly into a myriad of pixels. There are about 48 concave and convex lines per centimeter of cylindrical grating plates. There are about 6 pixels below each concave and convex line. It is not easy to control the precise alignment of the grating lines with the grating lines on the printed matter. The printing process directly printed on the grating material is relatively easy, and the finished product can be directly printed as long as the machine precision is achieved. However, unlike traditional printing, it is finally necessary to apply a layer of white varnish on the printing surface.
Although the theory of stereoscopic imagery suggests that the Lord has a history of less than 100 years, the practical application of this technology has been very long. The 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 stereo photographs, stereo photographs have great limitations in application and high precision on equipment precision, complicated process technology and high production cost. Therefore, stereo photography has not been promoted and popularized, and stereo printing has been subjected to a cumulative error between the pre-press process and a large process. Difficult operation, low efficiency, poor quality, high scrap rate, and expensive special manufacturing equipment and consumables are also the reasons that greatly hinder the application and development of raster stereo printing technology.
Stereoscopic photography in the 21st century enters 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-synthesized stereoscopic images.
With the advent of computer-to-plate CTP technology, high-precision printing using FM dots is adopted. UV technology applications continue to mature, and many equipment manufacturers have introduced various types of UV offset presses. The direct printing of plastic grating materials by offset printing machine is no longer a problem. The three-dimensional printing quality system has been guaranteed. The three-dimensional printing of gratings has been rapidly developed. In recent years, domestic three-dimensional printing has been greatly developed. The printing house began to use the grating stereo printing process to obtain more complex products. From labels, posters to packaging products, and even plastic cups, there is a thriving scene of application of stereo printing.
Although the stereoscopic visual effect is not really seen on the product, raster stereo printing is not just a trick to tease children. Compared with the traditional stereo photo production process, it shows its unique advantages in terms of economy and flexibility of use. We have reason to believe that the grating stereo printing technology will have wider application space and development in the future printing field. prospect.