How much do you know about the principle and techn

Analysis of stereoscopic printing: how much do you know about the principle and process technology?

in the printing field, stereoscopic printing, which reproduces the stereoscopic image of an object in three-dimensional space, has become an important content in the special printing industry. Here are the technical characteristics and development prospects in this regard

the principle and characteristics of stereoscopic printing

the principle of stereoscopic printing is to simulate the distance between human eyes, shoot from different angles, and record the left and right pixels on the photosensitive material. When viewing, the left eye sees the left pixel and the right eye sees the right pixel. The printed matter produced according to this principle is called stereoscopic printing

stereo printing has the following characteristics: (1) it can reproduce objects realistically and has a strong sense of three-dimensional. The product image is clear, the level is rich, the image is lifelike, and the artistic conception is profound; (2) The originals of stereoscopic printing are often made of modeling design or scenery shooting, and the printed matter is generally printed with high-quality coated paper and high-temperature resistant ink, so it has good gloss, bright color and is not easy to fade; (3) The surface of the printed product is covered with a layer of concave convex cylindrical mirror grating plate, which can directly watch the three-dimensional effect of the panoramic picture. From the perspective of people's stereovision of objects, stereovision of objects mainly comes from human physiological factors, experience and psychological factors. In fact, stereoscopic vision is the stereoscopic information formed by integrating these complex factors in the visual process. In terms of physiological factors, there are parallax (binocular parallax and monocular motion parallax), convergence, regulation, etc. Specifically, binocular parallax is the fundamental factor for people to obtain stereo vision, that is, in daily life, when people observe objects, due to the angle of view between the two eyes and other reasons, the object images seen by the left and right eyes will be different, that is, parallax, which gives people a sense of three-dimensional

the effect of stereoscopic images must be reflected by display technology. The stereoscopic display mentioned here refers to the reproduction of stereoscopic information in the three-dimensional space of an image, which is another basic condition for obtaining stereoscopic vision. There are mainly two methods to realize stereoscopic display, namely, two-way display method and multi-way display method

(1) two-way display method. It can be divided into stereoscopic method, two-color filter method, polarizing filter method and alternating segmentation method. No matter which method is adopted, stereo vision is obtained by using the parallax of two eyes to observe the image respectively by left and right eyes. Stereoscopic method: the basic principle of stereoscopic method is to use stereoscope to observe the left and right graphics to form a stereoscopic sense. This method has been widely used since it appeared in the 19th century, but special stereoscope must be used, otherwise there will be no stereo vision. Two color filter method: the left and right images are printed in the same plane with red and blue inks respectively, and the printed images are observed through the red and blue filters. Because the color filter and ink are complementary to each other, the image observed through the color filter is not red and blue, but black. Therefore, this method is limited to black-and-white photos and is not suitable for color printing. Coupled with different wavelengths of light entering the two eyes, it is easy to make the eyes tired. Therefore, this method is rarely used except for making aerial maps. Polarizing filter method: project the left and right images on the same plane through mutually orthogonal polarizing filters, and observe the left and right eyes with the same polarizing filters. Although this method requires special glasses, it has been widely used in stereoscopic movies and stereoscopic TVs. Alternate segmentation method: the left and right images are alternately presented on the same plane, and the unnecessary parts in the same period are covered, so as to produce a three-dimensional sense. Because the residual image effect will cause flash, and the price of glasses for masking is high, this method has not been popularized so far

(2) multidirectional display method. There are mainly parallax shielding method and cylindrical lens method. Parallax shielding method: parallax shielding method, also known as parallax slit method, was invented by es in 1930. Its working principle is to segment the left eye image and the right eye image by the slit, expose them on the film, and then develop, print and print. If it is placed in the same position when photographing, and the two eyes are also placed in the position where the image is placed, the stereoscopic image can be seen. Using the parallax slit method, if the two images are synthesized, the parallax stereo image can be obtained. If the aperture ratio of the slit is reduced, the synthesis of multiple images can be completed, and the parallax panoramic image can be obtained. In essence, the parallax slit method is inevitable to reduce the amount of light. Therefore, it is rarely used except in cylindrical lens photography. Cylindrical lens method: cylindrical lens can be regarded as a lens plate composed of many convex lens sheets side by side, which has the function of image division. The back of this lens coincides with the focal plane. Due to the image splitting effect of the lens, the images a, B, C and D in each direction can be separated into a, B, C and D and recorded on the focal plane. As long as the left and right eyes are placed at the positions of B and C, the stereoscopic image can be seen

process and key points of stereo printing

photography method of stereo printing

as mentioned above, cylindrical lens stereo printing requires images of the illuminated object seen from all directions. Photography methods include (1) circular arc moving method. This method takes a certain point on the subject as the center of the circle, and the distance from this point to the camera as the radius to make an arc. The camera moves along this arc and takes pictures continuously or intermittently; (2) Parallel moving method. Move the lens in parallel around the center line of the object. When shooting with this method, the accuracy is not easy to master; (3) Straight line shaking method. The captured image will be a little out of shape. However, if higher accuracy is not required, this is a simple method

in addition, the cylindrical lens is not used in photography. Like ordinary cameras, images in all directions are synthesized through the cylindrical lens while moving. Therefore, the images in all directions (6-9 pieces) cannot be continuous. It mainly includes instantaneous photography. The camera with multiple (6-9) lenses is most suitable for outdoor photography, especially the photography of moving objects, because it is easy to carry. However, stereoscopic photos cannot be formed without post synthesis. When image synthesis, it has the advantage of magnifying the size. Ordinary camera moving method: install the ordinary camera on the electric chute and take photos while sliding. Compared with the above instantaneous photography method, it has no outstanding advantages, but there is no need for a special camera. The method of using cylindrical lens in photography can continuously photograph within the effective angle. Stereoscopic images can be obtained at one time, but it is very difficult to enlarge after photography, and the exposure time is long, so moving objects cannot be photographed, and the camera is large, which is not suitable for handling. The subject moving method is the opposite of moving the camera. It makes the illuminated object rotate and move in a straight line

the center of the large turntable is consistent with the center of the subject, and photography is carried out while the turntable moves. Use a special indoor camera, which cannot shoot moving objects; Camera parallel moving method: use the method of parallel moving camera to take isometric photography of the subject. With the parallel moving, the camera is always aligned with the center of the subject, and a good image can be obtained. However, the camera is very difficult to make, and due to structural constraints, it is only used for indoor photography; Camera straight-line shaking method: This is a slightly simpler method than the above parallel moving method. The camera moves left and right in a straight line, and the lens shakes repeatedly to align with the center of the subject. This method can be used for indoor and outdoor photography; Shutter moving method: this shooting method is limited to indoor close-up cameras. The shutter moving method uses a large aperture lens. With the movement of the shutter in the lens, stereoscopic images in all directions can be taken. This method has less lens moving distance, can be exposed in a short time, and close-up photography will not damage the sense of three-dimensional, especially suitable for portrait photography

at present, there are two methods commonly used to shoot stereoscopic printing originals, namely, arc stereophotography and shutter moving method. Circular arc moving shooting: install the cylindrical lens plate directly in front of the photosensitive sheet, and shoot with a camera whose optical axis is always facing the center of the subject. The total distance of camera movement shall meet the requirements of image reproduction. Generally, it is controlled at the included angle of 3 ° - 102. The deformation measurement is measured through the deformation measurement installation. The grating plate in front of the photographic plate of the camera moves randomly and synchronously with the photographic plate. Each exposure will focus into a pixel under each semicircular column of the grating plate. When the camera finishes shooting at a predetermined distance, pixels fill the entire grid distance. Stereoscopic photos can be obtained after development. Shutter moving shooting: when shooting, the distance of the shutter moving from one end of the lens to the other is 60mm, which is equivalent to the distance between human eyes. At the same time, the grid plate close to the front of the photosensitive sheet also moves correspondingly, and the moving distance is a grid distance, that is, 0.6mm

plate making and printing process

due to the delicate pixels of stereo images and the amplification of cylindrical grating, the number of plate making lines must be more than 120 lines/cm. Stereoscopic printing is different from ordinary color printing, and the blue and black versions should adopt the same eye angle. In addition, stereo printing with different grid spacing should have different line combination angles of yellow, magenta, cyan and black plates to avoid interference fringes. Nowadays, the adding angle used by general manufacturers at home and abroad is: 0.6 grid spacing/cm, 100 lines/cm color separation, then the degree of adding angle is y81, M36, C66, K66; 0.44 grid pitch/cm, 58 lines/cm color separation, then the degree of adding angle is Y50, M20, C65, K65; 0.31 grid pitch/cm, 81 lines/cm color separation, then the degree of adding angle is y66, M22, C51, K51

because the stereoscopic manuscript is composed of closely arranged pixels, and the cylindrical mirror plate is also compounded after plate making and printing, when selecting the line angle, in addition to the moire formed between plates, we should also pay attention to the moire formed by the screen angle, pixel line and cylindrical mirror plate line

for example, 0 degree should not be selected for stereo printing, because the horizontal line is the most obvious, and 0 degree is orthogonal to the pixel line and the column mirror line, which interferes with the figure. In this paper, combined with China's material testing standard image, it is not easy to reinstall the clarity and depth of the software. In stereoscopic printing, the green and black plates have the same angle, which is determined by its own characteristics. Because the stereoscopic printing will eventually be combined with the plastic plate, and most of the column mirror plate has a certain gray level, and because the stereoscopic printing uses a very fine 300 line screen, it only needs to be exposed to 85% or 90% when printing, otherwise it is easy to paste the plate when printing, so it is necessary to increase the color amount of the dark tone area to achieve the effect of 9-9.5%. Therefore, the field density of color ink in stereo printing is higher than that in plane four-color printing. Generally: offset lithography: y:1-1.1, m:1 5，C:1.. 6； Stereoscopic printing: y:1 35，M:1.. 33，C:2。 If the three color printing ink is close to neutral gray after overprint, in order to reduce the error caused by the fourth overprint, there is no need to print the black version again. You can take the same angle between the black version and the green version for flexibility. In small format continuous exposure, the temperature of the exposure light source will cause the negative film to shrink, causing the grid distance between the front and back frames to change, affecting the printing cleaning method: take out the damping needle and use a trowel to correctly remove the component orientation accuracy along the axis of the damping needle, so it is best to connect the color separation film into a whole negative film for printing

when copying the positive image, it is necessary to close the line sheet with the same width as the grid distance between the negative film and the photosensitive film. The PS version with good hierarchical expressiveness should be used for the sun printing plate. The printing method selected for stereoscopic printing should ensure that it is not due to printing