Key Technology of Stereo Printing and Its Application Analysis (I)
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In the field of printing, the three-dimensional reproduction of stereoscopic image printing of objects - three-dimensional printing has become an important content in the special printing industry. Let's talk about the technical characteristics and development prospects in this area.
First, the principle and characteristics of three-dimensional printing
The principle of three-dimensional printing is to simulate the distance between two eyes of a person. From different angles, the left and right pixels are recorded 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 For three-dimensional printing.
The three-dimensional printing has the following characteristics: (1) The object can be reproduced realistically, and has a strong three-dimensional feeling. The product image is clear, the layer is rich, the image is realistic, and the artistic conception is deep; (2) the manuscript of the three-dimensional printing is often formed by the design or the scene, and the printed matter is generally selected as high-quality coated paper and high-temperature ink printing, so the gloss is good. The color is bright and not easy to fade; (3) The surface of the printed product is covered with a layer of concave and convex mirror-shaped grating plate, which can directly view the stereoscopic effect of the panoramic picture. From the perspective of stereoscopic vision of objects, the stereoscopic vision of objects is mainly derived from human physiological factors, experience and psychological factors. In fact, stereo vision is the stereoscopic information that people combine to form these complex factors of appeal in the visual process. From the physiological point of view, there are parallax (two-eye parallax and monocular motion parallax), convergence, and regulation. Specifically, binocular parallax is the fundamental factor for people to obtain stereoscopic vision. In daily life, when people observe an object, the image of the object seen by the left and right eyes will be different due to the angle of view between the two eyes. Parallax, it gives people a three-dimensional sense.
The effect of a stereoscopic image must be reflected by the display technology. The stereoscopic display referred to herein 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 two main methods for realizing stereoscopic display, namely, two-way display method and multi-directional display method.
(1) Two-way display method. Can be divided into stereoscopic method, two-color filter method, polarized color filter method and alternating segmentation method. Regardless of which method is adopted, stereoscopic vision is obtained by separately observing the image by using the left and right parallax eyes. Stereoscopic method: The basic principle of the stereoscopic method is to use a stereoscopic mirror to observe the left and right patterns to form a three-dimensional effect. This method has been widely used since the advent of the 19th century, but special stereoscopes must be used, otherwise there will be no stereoscopic vision. Two-color filter method: a method in which left and right images are printed in the same plane with red and blue inks, and the printed image is observed through red and blue color filters. Since the color filter and the 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 photographs and is not suitable for color prints. In addition, light of different wavelengths enters both eyes, which is easy to cause eye fatigue. Therefore, this method is rarely used except for the use of aerial maps. Polarized color filter method: The left and right images are respectively projected on the same plane through polarized color filters that are orthogonal to each other, and the left and right eyes are also observed by the same polarizing filter. Although this method requires special glasses, it has been widely used in stereoscopic movies and stereoscopic televisions. Alternate segmentation method: The left and right images are alternately presented on the same plane and the unnecessary portions of the same period are masked, thereby generating a stereoscopic effect. Since the afterimage effect causes flashing, and the cost of shielding glasses is high, this method has not been popularized so far.
(2) Multi-directional display method. There are mainly parallax shielding methods and cylindrical lens methods. Parallax screening method: Parallax shielding method, also known as parallax slit method, was invented by FELves in 1930. Its working principle is to divide the left eye image and the right eye image by slit and expose it on the film, and then develop it. , printing and printing. If you place it in the same position at the time of shooting, the two eyes are also placed at the position where the image is placed, and the stereoscopic image can be seen. By applying the parallax slit method, if two images are combined, a parallax stereoscopic image can be obtained. If the aperture ratio of the slit is lowered, the synthesis of a plurality of images can be completed, and a parallax panoramic image can be obtained. The parallax slit method is essentially inevitable in that the amount of light is decremented. Therefore, it is currently rarely used except for use in the photography of the cylindrical lens method. Cylindrical lens method: A cylindrical lens can be seen as a lens plate composed of a plurality of convex lens sheets side by side, which has a focusing effect. The back side of the lens coincides with the focal plane. Due to the image separation 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 in B and C. Position, you can see the stereo image.
Second, the three-dimensional printing process and points
1, three-dimensional printing photography method
As described above, cylindrical lens method embossing requires an image of an object to be seen from various directions. The photography method has (1) circular motion method. This method takes a point on the object as the center of the scene, and the distance from the point to the camera is a radius of the arc, and the camera moves along the arc to shoot continuously or intermittently; (2) Parallel movement method. Move the lens parallel around the centerline of the object. When shooting by this method, the accuracy is not easy to grasp; (3) Straight line shaking method. The image will be a little out of shape. But if you don't require higher precision, this is an easy way.
In addition, the method of using a cylindrical lens is not used in photography, and like a normal camera, photography is performed while moving, and then images in various directions are synthesized by a cylindrical lens. Thus the images in all directions (6-9 sheets) cannot be continuous. It mainly has instant photography. Cameras with multiple (6-9) lenses are ideal for outdoor photography, especially for moving objects, because of their portability. It is only that the stereoscopic photograph cannot be formed without post-synthesis, and has the advantage of being scalable when the image is synthesized. Ordinary camera movement method: Mount the ordinary camera on the electric chute and slide while shooting. Compared with the above-mentioned instant photography method, there is no outstanding advantage, but no special camera is needed. The method of using a cylindrical lens for photographing can continuously photograph within an effective angle. A stereo image can be obtained at one time, but it is very difficult to enlarge after photography, and the exposure time is long, the moving object cannot be photographed, and the camera is large in size and unsuitable for handling. The subject movement method is the opposite of moving the camera to rotate the object and move it linearly. The center of the large turntable coincides with the center of the subject, and the turntable moves while taking pictures. To use an indoor dedicated camera, you cannot shoot a moving object; the camera parallel movement method: equidistant photography of a subject by a parallel moving camera, and the camera always aligns with the center of the subject as it moves in parallel, Get good images. However, the production of the camera is very difficult, and due to structural limitations, it is only used for indoor photography; the camera is linearly shaken: this is a slightly simplified method than the parallel movement method described above. The camera moves straight to the left and right, and the lens is repeatedly shaken to the center of the subject. This method can be used indoors and outdoors; shutter movement method: This shooting method is limited to indoor close-range photography cameras. The shutter movement method uses a large-diameter lens, and stereoscopic images in all directions can be taken as the shutter moves inside the lens. In this way, the lens has a small moving distance and can be exposed in a short time, and the close-range photography does not damage the stereoscopic effect, and is particularly suitable for portrait photography.