In conventional printing, the images belong to the two-dimensional display range, but the information obtained by human vision belongs to three-dimensional information. From this point of view, the two-dimensional image display technology still has a lack of three-dimensional sense, that is, the three-dimensional sense of prints. Not strong enough. Then, how can we achieve the development of printing images from two-dimensional display to three-dimensional image display? People through the unremitting research and experiment, to absorb the characteristics of three-dimensional film, television, and finally developed a three-dimensional space reproduction object stereo image printing - three-dimensional printing, Nowadays, three-dimensional printing has become an important content in the special printing industry, and it has brilliance in many printing fields.

First, the characteristics of three-dimensional printing

The principle of three-dimensional printing is to simulate the distance between two eyes of a person and shoot from different angles. The left and right pixels are recorded on the photosensitive material. When viewed, 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. Three-dimensional printing has the following main features: (1) It can reproduce objects realistically and has a strong three-dimensional effect. Product images are clear, rich in levels, vivid in image and profound in artistic conception; (2) The manuscripts of three-dimensional printing are often made of design or scenery, and the printed matter is generally selected from high-quality coated paper and high-temperature resistant ink, so the gloss is good. Bright colors, difficult to fade; (3) printed product surface covered with a concave and convex cylindrical mirror grating board, you can directly view the three-dimensional effect of the panoramic picture.

From the perspective of people's stereoscopic vision of objects, the stereoscopic vision produced by objects is mainly based on human physiological factors, experience, and psychological factors. Physiological factors, there are parallax, convergence, adjustment and so on. In terms of experience and psychological factors, there are mainly retinal imaging size, line perspective, air perspective, density gradient, shadow, overlap, non-uniform composition, vision advance color, and retrograde color. The effect of stereoscopic images must be reflected by display technology. The stereoscopic display 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.

To achieve three-dimensional display are: (1) two-way display method. A stereoscopic method (basic principle is the stereoscopic effect of using a stereoscope to observe the left and right graphics) and a two-color filter method (printing the left and right images in the same plane with red and blue inks, respectively. Blue and color filters for viewing printed images), polarizing filters (left and right images are respectively projected on the same plane by orthogonal polarizing filters, left and right eyes are also observed by the same polarizing filter) and alternate division Method (left and right images are alternately presented on the same plane and unnecessary parts of the same period are masked to create a three-dimensional effect). Whichever method is used, stereoscopic vision is obtained by using the binocular parallax and left and right eyes respectively to observe the image. (2) Multi-directional display method. There are parallax shielding methods and cylindrical lens methods. Parallax Shielding, also known as parallax slitting, was invented by FEIves in 1930. Its principle is to divide the left-eye and right-eye images by slits and expose them on the film, then develop, print, and print. If you place it in the same position at the time of photography, and both eyes are placed at the position where the image is placed, stereo images can be seen. The cylindrical lens method, that is, the cylindrical lens can be regarded as a lens plate composed of a plurality of convex lens pieces side by side, and it has an imaging effect. The back of this lens coincides with the focal plane. Due to the separation 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 on the B and C. Position, you can see stereo images.

Second, the three-dimensional printing process points

1. Photography method and process

As described above, the cylindrical lens method for stereoscopic printing requires an image of an object to be viewed from various directions. Photography methods include arc movement method, parallel movement method, and linear vibration method. The method of using a cylindrical lens can continuously photograph within an effective angle. A stereoscopic image can be obtained at one time, but it is very difficult to enlarge the image after shooting, and the exposure time is too long to capture a moving object, and the camera is large in size and should not be carried. In addition, the cylindrical lens is not used for photography, and it is photographed while moving as with a normal camera, and then the images in each direction are synthesized by a cylindrical lens. Therefore, the images in each direction (6 to 9 sheets) cannot be continuous. It mainly has instant photography. However, this method cannot form a three-dimensional effect without post-production.

The methods commonly used for photographing three-dimensionally printed manuscripts include arc stereography and shutter movement. Circular arc photography method: The cylindrical lens plate is directly attached to the front of the photosensitive sheet and photographed with a camera. The optical axis of the camera is always at the center of the subject. The total distance of the camera movement is based on the requirements of the reconstructed image, and is generally controlled at an angle of 3 to 10 degrees. The grating plate in front of the camera photographic plate and the photosensitive plate move randomly and synchronously. Each exposure is focused to one pixel under each half cylinder of the grating plate. When the camera finishes shooting at a predetermined distance, the pixels fill the entire pitch. After washing can get a three-dimensional photo. Shutter movement method: When shooting, the distance from the head to the head of the lens is 60mm, which is equivalent to the distance between two eyes. At the same time, the grid plate immediately in front of the photosensitive sheet also moves accordingly, and the moving distance is a pitch of 0.6 mm.

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