Image classification of three-dimensional images

What is the origin of 3D images? It boils down to "visual transfer". Let's talk about the most important thing in the world-eyes. People's eyes are about 6 cm apart, which means that if you look at an object, your eyes look from the left viewpoint and the right viewpoint respectively. The left eye will see the left side of the object, while the right eye will see her middle or right side. When the object seen by both eyes is imaged on the retina, the left and right impressions are combined to get the final stereoscopic impression. And the effect of this stereoscopic effect is "visual displacement".

When shooting images, just use two cameras to simulate the parallax between the left and right eyes, shoot two films respectively, and then show the two films to the screen at the same time, and add necessary technical means when showing, so that the audience can only see the left eye image with the left eye and the right eye image with the right eye. After the last two images are superimposed by the brain, we can see a picture with three-dimensional depth. This is what we call a 3D image. Let's talk about several different principles of 3D.

Early black and white stereoscopic image: red and green filter lens

I think everyone has seen this kind of glasses, which were very common when I was a child. We can try to write on a piece of white paper by ourselves with a red pen and a green pen. After passing through the red lens, the white paper turns red, so the eyes can't see the words written by the red pen, but they can see the words written by the green pen. Of course, when you look at the paper through the green lens, you can't see the green words, only the handwriting of the red pen. According to this principle, two eyes can see different pictures taken by two cameras through the filter processing of red and green glasses, and the last two pictures are superimposed to form stereoscopic vision, which is the red and green filter lens technology of early stereoscopic movies. This technology is relatively simple to implement and the cost is low.

Early Color Stereo Images: Fractional Polarized Stereo Images

This is also a common stereo imaging method. Ordinary light travels along a wavy route, just like a person shaking a long rope. If the light wave passes through a special lens, only one kind of vibration light wave is allowed to pass, just like setting a fence on a fluctuating rope. As a result, the fluctuating rope can only pass through the fence in the vertical direction, but not in the parallel direction. This special lens is called "polarizer". The effect of early color stereoscopic movies was formed by the polarization of light. Stereo movies use a left camera and a right camera to shoot the same scene at the same time. During the screening, two projectors are used, and each projector is equipped with a polarizer to project the images of two polarized lights onto the screen at the same time, so that the vibration directions of the two polarized lights can be at right angles to each other. The audience should wear special polarized glasses when watching movies. The polarized light transmitted by the left and right lenses is perpendicular to each other, so the polarized light that can pass through the left eye cannot pass through the right eye, and the polarized light that can pass through the right eye cannot pass through the left eye. In this way, the lens of the left eye only allows the image of the left camera to pass through, while the lens of the right eye only allows the image of the right camera to pass through, and finally a color stereoscopic image appears.

The most convenient to watch: naked-eye 3D stereoscopic image

For friends who are already nearsighted, it is really painful to wear a pair of 3D glasses. What is the ideal 3D viewing effect? You have to be naked to see the 3D effect. Japanese company fujifilm has sold digital cameras that can take 3D photos and videos. This is the first digital camera in the world that can enjoy stereoscopic images with naked eyes without professional glasses. This camera has two Fuji long lenses and two CCD sensors. The two lenses on the camera body can shoot two pictures from two angles at the same time, and the difference is not big. Combining the two pictures through the newly developed portrait processing technology can produce 3D effect. Users can watch stereo photo and videos on the 2.8-inch LCD screen on the back of the camera without wearing special glasses. Anyone can shoot a stereoscopic effect by pressing the shutter. In addition to the camera's own display screen, users can also watch 3D photos and videos through retail dedicated digital photo albums. In addition, fujifilm also provides 3D photo development service, and uses special coating technology to control the direction of light propagation, so as to achieve naked-eye 3D effect.

"Naked-eye" 3D technology is not yet mature, but some home appliance manufacturers have developed some TVs that can see stereoscopic images without glasses, and scientists are also trying to use holographic imaging technology to achieve stereoscopic effects and successfully apply it in some large-scale activities. In terms of cinemas, Real D Company of the United States announced that it would let audiences take off 3D glasses and watch 3D movies directly within 10 years. By then, it will be more convenient and comfortable for viewers to watch 3D movies.

How are 3D images formed in the brain?

The gradual popularization of 3D movies and 3D TV brings us visual shock, but also brings us a series of problems. We live in a three-dimensional world, so it is natural to look at the world from a three-dimensional perspective. The birth of 3D technology is the product of a high combination of visual needs and scientific and technological development. So, how are 3D images formed in the brain? What effects do 3D movies and 3D TV have on our bodies, especially our eyes?

3D is the abbreviation of three-dimensional solid, which means that objects are distributed in three directions in space, namely, left and right direction, up and down direction and front and back direction. When our eyes observe an object, we can not only see its length and height, but also see its depth. This is because our eyes have different perspectives. When this difference is transmitted from the retina to the brain, we can distinguish the front and back distance of the object and produce a stereoscopic effect, which is stereoscopic vision.

When we record with photos, TV and movies, we transform the three-dimensional real scene into a two-dimensional plane image. If we want to see a three-dimensional image from a plane image, we need to make the same image into two images according to the difference between our eyes, so that our eyes can see one image respectively, and through the fusion of our brains, we can produce a three-dimensional effect. There are three ways to change a plane image into a stereoscopic image, namely, eye mode, glasses mode and screen mode.

The eye mode is naked eye mode. Our eyes turn in the same direction at the same time. When we look left, we all turn left. Look up and turn up. There is only one case where the eyes turn in the opposite direction, that is, the eyes can turn inward. This is the function of eye convergence, which is a unique function to adapt to close-up viewing. There is a kind of stereoscopic painting, which consists of a series of repeated patterns. When the eyeball is highly condensed and forms a "cross-eyed", a three-dimensional image is seen. This method can also be used to watch stereoscopic movies. When watching a movie clip showing the same content side by side, you can see three images, and the middle image is stereoscopic. This mode can only be used for a short time, and it will cause visual fatigue after a long time.

Glasses mode allows us to feel the three-dimensional sense through glasses. Common methods include color difference method, polarization method and shutter method. Color difference method is commonly used in early stereoscopic movies. Through the filter, the eyes can see different colors of the same object, resulting in a three-dimensional effect. Polarization method is to make polarized light in horizontal direction and vertical direction pass through a polarizer in two eyes respectively, thus creating a stereoscopic impression. Shutter method is to put on shutter glasses and control the opening and closing of glasses, so that we can see the images of the left and right eyes respectively and form a 3D image in the brain. Cinema mostly adopts polarization mode, and 3D TV adopts polarization mode and shutter mode.

Screen mode is a more advanced naked-eye mode, which gives the task of binocular stereo imaging to the screen. Generally used in televisions, mobile phones and game machines, parallax barrier technology and cylindrical lens technology are mainly adopted. The common feature of the two technologies is to separate the visual images of the two eyes by changing the screen, so that the left eye can see the "left eye image" and the right eye can see the "right eye image". Through the fusion of the brains, we can see the 3D image. This is the future development direction of 3D TV.

The above three modes all convert plane images into three-dimensional images, and another way to watch three-dimensional images is holographic mode. Holographic image is a pure three-dimensional model, which represents three-dimensional objects in the form of light and can show slight warping. It can be observed from all directions. It is virtual, you can only see it, but you can't touch it. This kind of holographic image also exists in life, and it is a mirage. This mode is often used in film production, which can show scenes that are not available in the real world and enrich people's lives.

Not everyone can see stereoscopic images. Some people suffer from stereoscopic blindness and cannot produce stereoscopic vision. Some people have abnormal stereoscopic vision, or their binocular vision is very different, so it is difficult to produce stereoscopic vision. These people had better not watch 3D movies and TV.

Some people will have nausea, dizziness, dry eyes, soreness and other symptoms after watching 3D movies, and even have an acute attack of glaucoma. Watching 3D movies won't hurt your eyes. Some people will feel sick and dizzy after watching 3D movies, which may be related to the strong acousto-optic effect of the cinema and the clarity of the film. Dry and sore eyes may be related to watching the screen for a long time and blinking less. The acute attack of glaucoma is related to the dark environment of the cinema. In a dark environment, people with narrow corners are prone to glaucoma, and watching ordinary movies in cinemas can also happen.

People are more concerned about the effects of watching 3D TV on their eyes. Most people seldom go to the movies, but watch TV at home. From watching 2D TV to watching 3D TV, the quality of life has been greatly improved, but people don't know how to choose dazzling 3D TV. 3D TV is mainly divided into time-sharing mode and light-splitting mode. Time-sharing mode uses active shutter glasses to achieve 3D effect. The images of the left eye and the right eye on the TV screen are played in chronological order. With the opening and closing of glasses, the right eye only sees the "right eye image" and the left eye only sees the "left eye image", and 3D vision is synthesized in the brain. This mode has no effect on the image definition, because the left and right eyes play the image quickly, which will cause flicker. Beam splitting mode is to attach a polarizing film to the TV screen, so that the light emitted by the TV is only horizontally polarized light and vertically polarized light, and then with polarized glasses, the eyes can see polarized light in different directions, forming 3D vision in the brain. This mode will affect the clarity of the image because the image is compressed in up-down format, left-right format or horizontal staggered format, but it is also called non-flash 3D TV because there is no image transformation. Watching 3D TV is different from watching 3D movies in the cinema. Audio and indoor lighting can be adjusted freely, and you can walk freely when watching TV. Therefore, eye and physical problems that occur when watching 3D movies may be less common when watching 3D TV. Some experts pointed out that the visual effect of 3D is not exactly the same as the real 3D we usually see with our eyes. In order to adapt to this change, we need more brain fusion, which may easily lead to headaches. In order to adapt to this change, the eyes will be over-regulated, resulting in visual fatigue.

Three-dimensional movies use two adjacent cameras to shoot "left eye image" and "right eye image" respectively, and both eyes can see their own images at the same time, forming a 3D image. At present, there are some shortcomings in time-sharing and spectrum-sharing of 3D TV. The ideal 3D TV should be a comprehensive simulation of human stereoscopic vision. We expect naked-eye 3D TV to solve these problems, which will be the highest level of artificial stereoscopic vision.

Technical classification

3D display technology can be divided into glasses and naked eyes. Naked 3D is mainly used in public business occasions, and will be applied to portable devices such as mobile phones in the future. In the field of household consumption, whether it is a monitor, a projector or a TV, it needs to be used with 3D glasses. There are two kinds of mainstream glasses 3D technology: the non-flash 3D TV mode is the most natural way, which is closest to the stereoscopic effect we actually feel. Just like enjoying a vivid 3D image in a cinema, you can watch two images at the same time and stick a special film on the surface of 3D TV and glasses to separate the left image from the right image. The left and right images are separated by TV and sent to glasses at the same time. Through the filtering of glasses, the separated left and right images are sent to each eye, and the brain synthesizes these two images, making people feel the 3D stereoscopic impression.

Features of non-flash 3D:

On the contrary, smart parents who are worried that their children are too close to the TV will affect their eye health are more willing to recommend the distance according to audio-visual rather than flash 3D. Moreover, because of the IPS hard screen panel, there is no limit to the left and right viewing angles, no matter which angle you look at, it is very sharp, and there is no color change. The flashless 3D TV can enjoy 3D images at any angle.

Advantages of non-flash 3D:

1. There is no flicker, which can reflect 3D images that are very comfortable for eyes. Non-flashing 3D has no electric drive, so it is very comfortable to wear glasses, and there is no flicker at all. In this way, you can enjoy 3D images that make your eyes very comfortable. Looking at the actual measured flicker data, we can know that the data is almost zero and there will be no dizziness.

2. Wide viewing angle. As long as you watch the non-flash 3D TV at any angle within the recommended distance, the picture effect and color expression will not be compromised, and you can enjoy the perfect and shocking 3D image without being limited by the angle.

3. Be able to enjoy 3D images with light and comfortable glasses. Non-flash 3D glasses are light in weight and reasonable in price. You can also use extra glasses to make people wearing glasses comfortable to use.

4. Reflect 3D images without overlapping images. Because the right image enters the left eye or the left image enters the right eye, the phenomenon of overlapping pictures appears. The special film used in non-flash 3D reflects the 3D image after separating the left image and the right image, so there will be no image overlap, and you can enjoy the stereoscopic image just like seeing a living object. By actually measuring the data of overlapping pictures, we can know that the overlapping data of non-flash 3D is at an imperceptible level.

5. You can reflect high-definition 3D images without dragging. Non-flash 3D can reflect 240 3D composite images in 1 sec. Therefore, in the same time, non-flash 3D can show more picture information, reflecting high-definition stereoscopic images without dragging.

In terms of viewing angle, it is not a problem to watch 3D without blinking within the recommended audio-visual distance. For example, except for standing, sitting or watching TV in a very abnormal posture within one meter, there is no problem watching TV within the recommended distance of 3D TV. Shutter 3D technology, English active shutter 3D, used with active shutter 3D glasses. This 3D technology is widely used in televisions and projectors, with relatively more resources and excellent image effects. It is highly praised and adopted by many manufacturers, but the matching 3D glasses are expensive.

Shutter disadvantages:

1, after wearing glasses, the brightness decreases even more;

2. The opening and closing frequency of 3D glasses is affected by the luminescence of fluorescent lamps, which leads to incomplete synchronization between the shutter opening and closing of 3D glasses and the left and right images, which may lead to crosstalk ghosting. It is recommended to turn off the lights when watching.

3. The price of shutter 3D glasses is basically around 1000 yuan, which is relatively expensive and needs to be charged or charged. Color separation method

At present, the color separation method is the most widely used method, in which images of different colors are superimposed, and then the superimposed images are separated and filtered with red and blue glasses to achieve the effect of depth of field. Advantages are low price of glasses, low technical threshold, low equipment requirements and low overall cost, but the effect is the most common. Disadvantages: The image is not displayed in full color.

Spectroscopy (polarization) method

Spectroscopy (or polarization) is widely used to make 3D movies. It uses two polarizers with polarization axes at 90 degrees to each other, which are placed in front of two projector lenses respectively, and then the images are superimposed to achieve 3D stereoscopic effect. For glasses, polarized lenses are also used. However, the cost of shooting production and hardware equipment is relatively high. Disadvantages: you need to wear glasses to look at the image horizontally.

Photometric method

Most 3d cinemas use spectroscopic 3d technology.

Time division method

Time-sharing method is the best method. It uses time difference to achieve 3D stereoscopic effect. It uses a high-frequency display to quickly switch left and right images through frequent frequencies; At the same time, glasses can also make the left and right lenses transparent, visible and closed, and repeat left and right; The overlapping images in the display are transmitted to the left and right eyes respectively, and the brain is calculated into a 3D stereoscopic image through the visual afterimage. Advantages: Full-color display, no position problem of viewing image. The application fields of 3D imaging technology are quite extensive, mainly including: 3D film post-production, 3D animation production, digital city construction, promotional film, virtual simulation, phantom imaging, stereoscopic cinema construction, 3D game production, exhibition, large-scale tour activities, 3D teaching, 3D medical imaging and other fields.